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Applied Surface Science (v.257, #7)

Editorial Board (pp. ii).

Nonpolar a-plane GaN grown on r-plane sapphire using multilayer AlN buffer by metalorganic chemical vapor deposition by C.H. Chiang; K.M. Chen; Y.H. Wu; Y.S. Yeh; W.I. Lee; J.F. Chen; K.L. Lin; Y.L. Hsiao; W.C. Huang; E.Y. Chang (pp. 2415-2418).

▶ Mirror-like and pit-free non-polar a-plane (11−20) GaN films are grown on r-plane (1−102) sapphire substrates using metalorganic chemical vapor deposition (MOCVD) with multilayer high-low-high temperature AlN buffer layers. The multilayer AlN buffer structure includes a thin low-temperature-deposited AlN layer inserted into the high-temperature-deposited AlN layer. The results demonstrate that the multilayer AlN buffer structure can improve the surface morphology of the upper a-plane GaN film.Mirror-like and pit-free non-polar a-plane (11−20) GaN films are grown on r-plane (1−102) sapphire substrates using metalorganic chemical vapor deposition (MOCVD) with multilayer high-low-high temperature AlN buffer layers. The buffer layer structure and film quality are essential to the growth of a flat, crack-free and pit-free a-plane GaN film. The multilayer AlN buffer structure includes a thin low-temperature-deposited AlN (LT-AlN) layer inserted into the high-temperature-deposited AlN (HT-AlN) layer. The results demonstrate that the multilayer AlN buffer structure can improve the surface morphology of the upper a-plane GaN film. The grown multilayer AlN buffer structure reduced the tensile stress on the AlN buffer layers and increased the compressive stress on the a-plane GaN film. The multilayer AlN buffer structure markedly improves the surface morphology of the a-plane GaN film, as revealed by scanning electron microscopy. The effects of various growth V/III ratios was investigated to obtain a-plane GaN films with better surface morphology. The mean roughness of the surface was 1.02nm, as revealed by atomic force microscopy. Accordingly, the multilayer AlN buffer structure improves the surface morphology and facilitates the complete coalescence of the a-plane GaN layer.

Keywords: GaN; Crystal morphology; Nonpolar; MOCVD

Femtosecond laser ablation profile near an interface: Analysis based on the correlation with superficial properties of individual materials by Gustavo Nicolodelli; Cristina Kurachi; Vanderlei Salvador Bagnato (pp. 2419-2422).

▶ Ultrashort laser ablation behavior in a interface between two solid media represents new challenges in the field. ▶ Laser ablation through interfaces of two materials was understood using ablation characteristics of each individual material. ▶ Once one understands the threshold behavior for ablation, the variations on the geometry of ablated region at the interface can be predicted. ▶ The size of ablation discontinuity at interface is dominated by the difference on the optical properties of the two mediun. ▶ This procedure can be applied for understanding ablation geometry on structured materials.Femtosecond laser ablation of materials is turning to be an important tool for micromachining as well as for selective removal of biological tissues. In a great number of applications, laser ablation has to process through interfaces separating media of different properties. The investigation of the ablation behavior within materials and passing through interfaces is the main aim of this study. Especially, the analysis of the discontinuity in the ablation profile close to interfaces between distinct materials can reveal some of the phenomena involved in the formation of an ablated microcavity geometry. We have used a method that correlates the ablation cross sectional area with the local laser intensity. The effective intensity ablation properties were obtained from surface ablation data of distinct materials. The application of this method allows the prediction of the occurrence of a size discontinuity in the ablation geometry at the interface of distinct media, a fact which becomes important when planning applications in different media.

Keywords: Femtosecond; Laser ablation; Micromachining; Interfaces

Fabrication of triazinedithiol functional polymeric nanofilm by potentiostatic polymerization on aluminum surface by Fang Wang; Yabin Wang; Yanni Li; Qian Wang (pp. 2423-2427).

▶ The functional polymeric nanofilm (PAF17) of 6-(N-allyl-1,1,2,2-tetrahydroperfluorodecyl)amino-1,3,5-triazine-2,4-dithiol monosodium (AF17N) was prepared on pure aluminum surface by potentiostatic polymerization at different potentials. The optimal electro-polymerization potential and time were investigated. The result showed that uniform and compact nanofilm of PAF17 could be obtained under these conditions. It is expected that this technique will be applied in the preparation of lubricating, dielectric and hydrophobic surface on aluminum substrate.The functional polymeric nanofilm of 6-(N-allyl-1,1,2,2-tetrahydroperfluorodecyl)amino-1,3,5-triazine-2,4-dithiol monosodium (AF17N) was prepared on pure aluminum surface by potentiostatic polymerization at different potentials. The thickness and weight of polymeric nanofilm increased proportionally to electro-polymerization potential following linear equation. The chemical structure of nanofilm was characterized by Fourier transform-infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Adsorption peaks in FT-IR and C1s, N1s, S2p, F1s and Al2p peaks in XPS spectra indicated that the polymeric nanofilm was poly(6-(N-allyl-1,1,2,2-tetrahydroperfluorodecyl)amino-1,3,5-triazine-2,4-disulfide) (PAF17). The morphologies of polymeric nanofilm were also observed by atomic force microscopy (AFM). All the results showed that the optimal electro-polymerization potential and time were 8V and 20s, respectively. Uniform and compact nanofilm of PAF17 could be obtained under these conditions. It is expected that this technique will be applied in the preparation of lubricating, dielectric and hydrophobic surface on aluminum substrate.

Keywords: Triazinedithiol monosodium; Aluminum surface; Functional polymeric nanofilm; Potentiostatic electro-polymerization

Structure, electrical and optical properties of TiN_x films by atmospheric pressure chemical vapor deposition by Gangfeng Duan; Gaoling Zhao; Ling Wu; Xiaoxuan Lin; Gaorong Han (pp. 2428-2431).

▶ We obtain TiN_x films with various x using APCVD. ▶ They were prepared on glass substrates at a relatively low temperature of 600°C. ▶ It is suitable for online coatings production. ▶ The composition affects the optical and electrical properties of TiN_x coating glass.Titanium nitride (TiN_x) films with various nitride compositions ( x) were prepared on glass substrates by atmospheric pressure chemical vapor deposition using TiCl₄ and NH₃ as precursors. The structural, compositional, electrical and optical properties of the films were studied and the results were discussed with respect to nitride composition. The results showed a linear relationship between the lattice constant and the nitride composition. Resistivity of the films was minimized near x=1. All the TiN_x films exhibited a transmission band with a peak value of about 15% in the visible region (400–700nm). As the wavelength increased to transition point ( λ_T-R), the reflectance of the obtained films presented a sharp increase and then reached a high value of about 50% near 2000nm. Moreover, the red-shift of transmission band and the transition wavelength ( λ_T-R) with increasing the nitride composition were also discussed.

Keywords: Titanium nitride; Nitride composition; Atmospheric pressure chemical vapor deposition; Structure; Optical properties

Femtosecond laser machining of electrospun membranes by Yiquan Wu; A.Y. Vorobyev; Robert L. Clark; Chunlei Guo (pp. 2432-2435).

▶ Femtosecond laser machining of PCL electrospun membranes. ▶ Useful platform for fabricating patterned structures on membranes. ▶ Ultrafast laser processing of materials can minimize and control deformation of electrospun fibers.We demonstrate that a femtosecond laser can be used to machine arbitrary patterns and pattern arrays into free-standing electrospun polycaprolactone (PCL) membranes. We also examine the influence of various laser irradiation settings on the final microstructure of electrospun membranes. A beam fluence of 0.6J/cm² is used to ablate holes in 100μm thick PCL membranes. The machined holes have an average diameter of 436μm and a center-to-center spacing of 1000μm. Based on these results, the femtosecond ablation of electrospun membranes shows great potential for fabricating a variety of functional tissue scaffolds. This technique will advance scaffold design by providing the ability to rapidly tailor surface morphology, while minimizing and controlling the deformation of the electrospun fibers.

Keywords: Laser machining; Electrospinning; Membranes

Stability and textural properties of cobalt incorporated MCM-48 mesoporous molecular sieve by Qian Zhao; Xuping Zhou; Meiru Ji; Haihui Ding; Tingshun Jiang; Changsheng Li; Hengbo Yin (pp. 2436-2442).

Display Omitted▶ Co-incorporated MCM-48 obtained via hydrothermal method possesses the Ia3d cubic mesoporous framework. ▶ The thermal and hydrothermal treatment results indicate that the resulting mesoporous materials have highly thermal and hydrothermal stabilities. ▶ With the increase in cobalt content, the specific surface area of the sample gradually decreased and the mesoporous ordering gradually deteriorated.Transition metal cobalt incorporated MCM-48 mesoporous molecular sieves (CoMCM-48) with different Co contents were synthesized hydrothermally at 120°C for 24h by directly adding fluoride ions to the initial gel. The resulting materials were characterized by means of XRD, TEM, FT–IR, UV–vis, TPR and N₂ physical adsorption, respectively. The effect of various factors, such as the Si/Co molar ratio, calcination temperature and hydrothermal treatment time, on the crystalline structure and textural properties of CoMCM-48 was investigated in detail. The results show that the CoMCM-48 mesoporous materials with high specific surface area were successfully synthesized. A small amount substitution of Co for Si in MCM-48 did not significantly change the textural properties while the higher cobalt incorporated leads to decrease of the surface area and deterioration of structural regularity. Furthermore, the resulting CoMCM-48 still retained the cubic mesoporous framework even after calcination at 800°C for 4h or hydrothermal treatment at 100°C for 24h.

Keywords: Co-incorporated mesoporous molecular sieve; Hydrothermal synthesis; Textural property; Stability

The rubbing supplemented atmospheric plasma process for tunable liquid crystal alignment by Oleg V. Yaroshchuk; Ruslan M. Kravchuk; Sergiy S. Pogulay; Vyacheslav V. Tsiolko; Hoi Sing Kwok (pp. 2443-2447).

▶ Atmospheric plasma processing by itself provides insufficient uniformity of liquid crystal alignment on macroscopic scale. ▶ The alignment can be radically improved by combination of plasma processing with rubbing or other process providing high surface anisotropy. ▶ The homeotropic-to-planar anchoring transition observed with the increasing of exposure dose is caused by destruction of hydrophobic chains on the treated surface resulting in increase of surface free energy.Processing of the liquid crystal (LC) aligning substrates by a flux of atmospheric plasma provides controllable pretilt angle and anchoring energy, but rather poor alignment uniformity on macroscopic scale. The result is however radically improved by combination of this process with rubbing. In this case, high-quality tilted alignment is realized with a pretilt angle continuously tuned in the range 0–90°. The corresponding cells show excellent electro-optic performance. This makes combination of atmospheric plasma and rubbing processes rather attractive for industry, especially for those cases where the LC pretilt angle and anchoring energy should be patterned or continuously tuned.

Keywords: PACS; 61.30.Hn; 61.30.Gd; 52.77.Bn; 81.65.−bLiquid crystal alignment; Plasma beam alignment; Ion beam alignment; Atmospheric plasma treatment

Methane non-oxidative aromatization on Mo/ZSM-5: Effect of adding triethoxyphenylsilanes into the synthesis system of ZSM-5 by Chen Xu; Heng Liu; Mingjun Jia; Jingqi Guan; Shujie Wu; Tonghao Wu; Qiubin Kan (pp. 2448-2454).

A series of ZSM-5 zeolites were synthesized by adding triethoxyphenylsilane (PTEOS) into the initial sol of the synthesis system. The samples were studied by XRD, SEM, N₂ adsorption–desorption and acid assessment of d₃-acetonitrile adsorption. Characterization results showed that the crystal size of the ZSM-5 zeolites could be adjusted in a certain range by introducing different contents of PTEOS. Besides, the resultant materials possess hierarchical porosity in addition to those micropores generated by the MFI channels. Moreover, supported Mo/ZSM-5 catalysts were prepared, and their catalytic performances were investigated in the methane non-oxidative aromatization. It was found that the Mo/ZSM-5 catalyst, bearing suitable crystal size and mesoporous characteristic showed relatively high shape-selectivity to benzene and high stability for the reaction of methane aromatization.

Keywords: ZSM-5; Crystal size; Triethoxyphenylsilane; Methane aromatization

Field emission characteristics of thin-metal-coated nano-sheet carbon films by Guang-Rui Gu; Toshimichi Ito (pp. 2455-2460).

Nano-sheet carbon films (NSCFs) coated with very thin (≈5-nm-thick) metal layers were fabricated on Si wafer chips by means of quartz-tube-type microwave-plasma chemical-vapour-deposition method with hydrogen–methane gas mixture and an electron beam evaporation method. Field emission (FE) current densities obtained at a macroscopic average electric field, E, of ≈10V/μm changed from 13mA/cm² for NSCF with no coated metal to 1.7, 0.7 and 30mA/cm² for Ti-, Al- and Au-coated NSCFs, respectively, while the threshold E varied from 4.4V/μm for the former one to 5.3, 5.4 and 2.0V/μm for the corresponding latter ones, respectively. As the FE currents of Au-coated NSCFs tended to be saturated in a higher E region, compared to those of NSCFs with no coated metal, no simple Fowler–Nordheim (F–N) model is applicable. A modified F–N model considering statistic effects of the FE tip structures and a space-charge-limited-current effect is successfully applied to an explanation for the FE data observed in the low and high E regions.

Keywords: Nano-sheet carbon films; Field emission; Microwave plasma CVD; Space-charge-limited-current

Adsorption and separation of propane and propylene by porous hexacyanometallates by G. Autie-Castro; M. Autie; E. Reguera; R. Moreno-Tost; E. Rodríguez-Castellón; A. Jiménez-López; J. Santamaría-González (pp. 2461-2466).

▶ Propane and propylene separation. ▶ Propane and propylene adsorption. ▶ Inverse gas chromatography. ▶ Prussian blue analogues. ▶ Molecular porous solids.The separation capability for mixtures of propane and propylene by porous frameworks representatives of transition metal hexacyanometallates was studied from adsorption data under equilibrium conditions at 273.15K and from inverse gas chromatography profiles at different column temperatures. Samples of two porous solids were considered; Cd₃[Co(CN)₆]₂, which is representative of Prussian blue analogues (cubic structure) with a porous framework related to vacancies for building block, and Zn₃[Co(CN)₆]₂ (rhombohedral phase) where the porous framework results from the tetrahedral coordination for the Zn atoms. The two materials were found to be able for the mixtures separation, with the highest separation ability for the rhombohedral phase under equilibrium conditions but, in dynamic conditions the cubic one shown a better separation, which was ascribed to a kinetic contribution related to a smaller windows size.

Keywords: Propane; Propene; Separation; Adsorption; Porous hexayanometallates

The effect of laser remelting in the formation of tunable nanoporous Mn structures on mild steel substrates by Chang-sheng Dong; Yu Gu; Min-lin Zhong; Lin Li; Ming-xing Ma; Wen-jin Liu (pp. 2467-2473).

▶ Nanoporous manganese was fabricated by a three-step process involving high power laser cladding of a homogeneous Cu₄₀Mn₆₀ alloy coatings onto a mild steel substrate, laser remelting for tuning the grain size and the composition homogeneity followed by selectively electrochemical de-alloying for removal of Cu element and formation of nanoporous Mn. This paper focuses on the influence of the laser remelting speed on the dentritic arm space and finally the nanoporous structure evolution. The microstructure and homogeneity of the precursor Cu₄₀Mn₆₀ alloys have a significant influence on the evolution of nanopores during selectively electrochemical de-alloying. Nanoporous Mn with nanopore sizes ranging from 80 to 130nm was fabricated by this method. It is found that smaller nanoporosity leads to significant improvements in surface-enhanced Raman scattering.Nanoporous manganese was fabricated by a three-step process involving high power laser cladding of a homogeneous Cu₄₀Mn₆₀ alloy coatings onto a mild steel substrate, laser remelting for tuning the grain size and the composition homogeneity followed by selectively electrochemical de-alloying for removal of Cu element and formation of nanoporous Mn. The microstructure and homogeneity of the precursor Cu₄₀Mn₆₀ alloys have a significant influence on the evolution of nanopores during selectively electrochemical de-alloying. Laser remelting can significantly refine the microstructure. The second dendrite arm spacing decreases with increasing of laser remelting scanning speed. A SDAS of 1.17μm was obtained at the laser scanning speed of 133mm/s. When the remelting scanning speed reaches 100mm/s, a nanoporous structure with average pore size less than 100nm was achieved under optimized dealloying electrode current density about 2mA/cm². Nanoporous Mn with nanopore sizes ranging from 80 to 130nm was fabricated by this method. Surface-enhanced Raman scattering characteristics of the nanoporous materials have been investigated. It is found that smaller nanoporosity leads to significant improvements in surface-enhanced Raman scattering.

Keywords: Microstructure; Nanoporous; Surface-enhanced Raman scattering (SERS); Laser remelting

Configuration and electronic properties of graphene nanoribbons on Si(211) surface by W. Wang; L.Z. Sun; C. Tang; X.L. Wei; J.X. Zhong (pp. 2474-2480).

▶ Configurations and electronic structures of GNRs on Si(211) surface have been inverstigated by using first-principles method. ▶ Bridge and M-shape adsorption configurations of GNRs on Si(211) surface appear gradually as the ribbon width increases. ▶ The Si(211) substrate effectively affects the edge states of GNRs and tends to depress the metallic nature of zigzag GNRs (Z-GNRs) and metallize the armchair GNRs (A-GNRs).We perform first-principles calculations based on density functional theory to study the configuration and electronic properties of graphene nanoribbons (GNRs) on Si(211) surface. Both [011¯] and [1¯11] adsorption orientations of Si(211) surface are considered. We find that the adsorption energy is determined not only by the edge states of GNRs, but also by the ribbon width and the orientation of the substrate. Bridge and M-shape adsorption configurations appear gradually as the ribbon width increases. The substrate effectively affects the edge states of GNRs and tends to depress the metallic nature of zigzag GNRs (Z-GNRs) and metallize the armchair GNRs (A-GNRs).

Keywords: Si(2; 1; 1) surface; GNRs; Adsorption; Electronic structure

Fabrication of microporous hollow silica spheres templated by NP-10 micelles without calcinations by Xian Wang; Xin-Rui Miao; Zhuo-Min Li; Wen-Li Deng (pp. 2481-2488).

Display Omitted▶ Nonionic surfactant nonyl phenol ethoxylated decylether (NP-10) was used as template to fabricate silica hollow spheres. ▶ Size and morphologies of the hollow spheres could be tuned by changing the concentration of silica sodium or core materials. ▶ The core materials were removed by ethanol during the reaction. ▶ Neither calcinations process nor solvent etching was necessary to remove the core materials.We reported a novel method to fabricate hollow silica microspheres using nonionic surfactant nonyl phenol ethoxylated decylether (NP-10) micelles as template, n-octadecane as core and sodium silicate as silica precursor. The core materials were removed by ethanol during the reaction. Hollow structure formed without calcinations or chemical etching. Hierarchical silica hollow microspheres were prepared by changing the concentration of the reactants and reaction time. Size of the core materials was obtained from the temperature-dependent dynamic light scattering (DLS) measurement. Scanning election microscopy (SEM) and transmission electron microscopy (TEM) results revealed that ordered microporous hollow silica microspheres with thickness of shell about 200nm and mean diameter 2.5μm were prepared. Porosity and pore size were analyzed by Brunauer–Emmett–Teller (BET).

Keywords: Hollow silica microspheres; Template; Non-calcination; Nonionic surfactant

Improvement in the photocatalytic activity of TiO₂ by the partial oxidation of the C impurities by Myoung Joo Kim; Kwang-Dae Kim; Hyun Ook Seo; Yuan Luo; Nilay Kumar Dey; Young Dok Kim (pp. 2489-2493).

TiO₂ was treated by water in an ultrasonic bath, resulting in the enhancement of the photocatalytic activity for the decomposition of methylene blue under UV and visible light irradiation. No change in the crystallinity and optical properties of TiO₂ by the H₂O-treatment was observed. The X-ray photoelectron spectroscopy (XPS) and FT-IR data revealed that the C impurities were oxidized by this treatment, indicating that the change in the structure of the C impurities plays a pivotal role in the photocatalytic activity of TiO₂.

Keywords: Photocatalysis; TiO; ₂; X-ray photoelectron spectroscopy (XPS)

Controlling surface shallow junction depth by a rapid thermal annealing process with low ambient pressure by Yi-Jen Huang; Chun-Chu Liu; Kuang-Yao Lo; Sheng-Yuan Chu (pp. 2494-2497).

We demonstrate the effect of annealing pressure on the redistribution of phosphorus dopants in silicon. The phosphorus concentration in the kink region is dependent on the annealing pressure that enhances the phosphorous transient out-diffusion. The phosphorous in-diffusion in the tail region is suppressed by this transient out-diffusion under low annealing pressure (below the atmosphere), and the surface shallow junction depth is reduced. The phenomenon of dose loss caused by the phosphorous piling-up or sublimation at the surface has an influence on the electrical characteristics and the surface roughness. Moderate annealing pressure can reduce the junction depth and only slightly increase the sheet resistance and surface roughness.

Keywords: Phosphorous diffusion; Rapid thermal annealing; Transient enhanced out-diffusion; Dose loss; Junction depth

Boron doped ZnO thin films fabricated by RF-magnetron sputtering by Li Gao; Yan Zhang; Jian-Min Zhang; Ke-Wei Xu (pp. 2498-2502).

▶ Both as-deposited and annealed ZnO:B films exhibit much lower resistivity as well as slightly broader optical band gap compared with pure ZnO film. ▶ These results are consistent with the first-principles calculations that in both ZnO:B films not only the band gap becomes narrower but also the Fermi level shifts up into the conduction band with respect to the pure ZnO film.By using the radio frequency-magnetron sputtering (RF-MS) method, both pure ZnO and boron doped ZnO (ZnO:B) thin films were deposited on glass substrates at ambient temperature and then annealed at 450°C for 2h in air. It is found that both ZnO and ZnO:B thin films have wurtzite structure of ZnO with (002) preferred orientation and high average optical transmission (≥80%). Compared with the resistivity of 6.3×10²Ωcm for ZnO film, both as-deposited and annealed ZnO:B films exhibit much lower resistivity of 9.2×10⁻³Ωcm and 7.5×10⁻³Ωcm, respectively, due to increase in the carrier concentration. Furthermore, the optical band gaps of 3.38eV and 3.42eV for as-deposited and annealed ZnO:B films are broader than that of 3.35eV for ZnO film. The first-principles calculations show that in ZnO:B thin films not only the band gap becomes narrower but also the Fermi level shifts up into the conduction band with respect to the pure ZnO film. These are consistent with their lower resistivities and suggest that in the process of annealing some substituted B in the lattice change into interstitial B because of its smaller ion radius and this transformation widens the optical band gap of ZnO:B thin film.

Keywords: ZnO thin film; Boron doped; RF-magnetron sputtering

Synthesis and characterizations of spherical hollow composed of AgI nanoparticle using AgBr as the precursor by Ming Yang; Kui Zhou (pp. 2503-2507).

Hollow spheres of AgI with an average radius of 100–200nm have been prepared by a simple reaction between AgBr suspension and KI in the presence of gelatin. Gelatin played a decisive role as an inhibitor of the direct attack of I⁻ ions to AgBr surfaces and coagulation of the growing AgI in producing the spherical AgI particles. The products were characterized by X-ray powder diffraction, transmission electron microscopy, UV–vis absorption spectroscopy and X-ray photoelectron spectra techniques. The band gaps are estimated to be 2.95eV according to the results of optical measurements of the hollow spheres of AgI.

Keywords: Silver iodide; Hollow spheres; Semiconductor

Direct current magnetron sputter-deposited ZnO thin films by Jian-Wei Hoon; Kah-Yoong Chan; Jegenathan Krishnasamy; Teck-Yong Tou; Dietmar Knipp (pp. 2508-2515).

▶ The effects of deposition parameters on the properties of ZnO films deposited on glass substrates are revealed in this paper. ▶ The granular structures of the ZnO films are enhanced with the increasing film thickness, deposition pressure and substrate temperature. ▶ Thinner film, higher deposition pressure and higher substrate temperature enhance the optical transmittance of the ZnO.Zinc oxide (ZnO) is a very promising electronic material for emerging transparent large-area electronic applications including thin-film sensors, transistors and solar cells. We fabricated ZnO thin films by employing direct current (DC) magnetron sputtering deposition technique. ZnO films with different thicknesses ranging from 150nm to 750nm were deposited on glass substrates. The deposition pressure and the substrate temperature were varied from 12mTorr to 25mTorr, and from room temperature to 450°C, respectively. The influence of the film thickness, deposition pressure and the substrate temperature on structural and optical properties of the ZnO films was investigated using atomic force microscopy (AFM) and ultraviolet–visible (UV–Vis) spectrometer. The experimental results reveal that the film thickness, deposition pressure and the substrate temperature play significant role in the structural formation and the optical properties of the deposited ZnO thin films.

Keywords: ZnO; Sputtering; Optical properties; Structural properties

Epitaxial relationships and optical properties of SnO₂ films deposited on sapphire substrates by Zhen Zhu; Jin Ma; Caina Luan; Lingyi Kong; Qiaoqun Yu (pp. 2516-2519).

▶ Epitaxy of SnO₂ on three types of sapphires. ▶ Epitaxial relationships were determined by X-ray phi-scans. ▶ Observation of a UV emission in SnO₂ film on r-cut sapphire.SnO₂ thin films were grown using metalorganic chemical vapor deposition (MOCVD) system on sapphire substrates with three different orientations: r-cut(011¯2), a-cut(112¯0), and m-cut(101¯0). All the deposited films were epitaxial rutile films. The epitaxial orientation relationships were determined by X-ray Φ-scans: [010]SnO₂||[100]Al₂O₃ and[101¯]SnO2||[1¯2¯1]Al2O3 for the r-cut substrate; [010]SnO₂||[001]Al₂O₃ and[101¯]SnO2||[11¯0]Al2O3 for the a-cut substrate; [010]SnO₂||[001]Al₂O₃ and [100]SnO₂||[010]Al₂O₃ for the m-cut substrate. The X-ray rocking curves yielded full width at half maximum (FWHM) of 0.78°, 1.32° and 0.70° for the (101) and (002) reflections of the SnO₂ films on r-, a-, and m-cut sapphire substrates, respectively. The room-temperature photoluminescence (PL) spectra of SnO₂ films grown on a-cut and m-cut substrates only showed a broad deep-level luminescence band. While a UV band-edge luminescence peak was observed for the film grown on r-cut substrate.

Keywords: SnO; ₂; film; Epitaxial relationship; MOCVD; Photoluminescence

Structural properties of pulsed laser deposited SnO_x thin films by E. Fazio; F. Neri; R. Ruggeri; G. Sabatino; S. Trusso; G. Mannino (pp. 2520-2525).

▶ Nanocrystalline SnO_x thin films were deposited by pulsed laser ablation at 470K. ▶ Almost stoichiometric films were grown in the presence of 13.3Pa of oxygen. ▶ Increasing the deposition oxygen pressure up to 66.7Pa a worsening of the structural properties was observed. ▶ SAED analysis shows that the unit cell shrinks along the principal crystallographic axes due to oxygen vacancies, according to the stoichimetric parameter values.Nanocrystalline SnO_x thin films were grown by means of pulsed laser deposition onto substrates held at relatively low temperature (470K) and by varying the background oxygen gas pressure up to 66.7Pa. The formation of the nanocrystalline structures in the films has been investigated in detail by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The results showed that, upon increasing oxygen gas pressure up to 13.3Pa, the laser induced plasma expands forming a shock wave and it is possible to obtain almost stoichiometric films composed of nanoparticles exceeding 10nm in size and essentially with a tetragonal rutile crystalline structure. Further increase of the oxygen pressure up to 66.7Pa induces a worsening of the material’s structural properties with a drastic reduction of the nanoparticles size down to 1nm and the development of a large amount of an amorphous phase. The analysis of the SAED patterns shows that the unit cell shrinks along the principal crystallographic axes, due to oxygen atoms vacant sites, in agreement with the stoichiometry parameter values determined from X-ray core level photoemission spectroscopy measurements.

Keywords: PACS; 81.16.Mk; 68.37.Lp; 61.46.DfTin oxide; Thin films; Pulsed laser ablation; TEM

Optical properties and thermal stability of LaYbO₃ ternary oxide for high- k dielectric application by Wei-tao Su; Li Yang; Bin Li (pp. 2526-2530).

▶ New ternary high- k dielectric oxide LaYbO₃ has high crystalline temperature (Tc>900°C). ▶ Wide band gap (∼5.8–6eV). ▶ High dielectirc constant ∼23.A new ternary rare oxide dielectric LaYbO₃ film had been prepared on silicon wafers and quartz substrates by reactive sputtering method using a La–Yb metal target. A range of analysis techniques was performed to determine the optical band gap, thermal stability, and electrical property of the deposited samples. It was found the band gap of LaYbO₃ film was about 5.8eV. And the crystallization temperature for rapid thermal annealing (20s) was between 900 and 950°C. X-ray photoelectron spectroscopy results indicate the formation of the SiO₂ and silicate in the interface between silicon wafer and LaYbO₃ film. The dielectric constant is about 23 from the calculation of capacitance–voltage curve, which is comparable higher than previously reported La₂O₃ or Yb₂O₃ film.

Keywords: High-; k; oxide; Ternary rare earth oxide; LaYbO; ₃; Physical properties

Influence of jet-to-substrate distance on plasma etching of polyamide 6 films with atmospheric pressure plasma by Zhiqiang Gao (pp. 2531-2535).

In this study, polyamide 6 films were treated with different jet-to-substrate distances to investigate how it influenced the etching effect of plasma treatment. When the samples were too close or too far from the nozzle, the etching rate was almost not measurable. When the distance was 2mm, the etching rate was larger than that of other distance. Decrease in contact angle was observed under 2mm or 3mm of jet-to-substrate distance. However, the contact angle had no change when jet-to-substrate distance was 1mm or 6mm. It can be seen that the peel strength increased when jet-to-substrate distance was 2mm or 3mm, and the peel strength was the largest when jet-to-substrate distance was 2mm. However, the peel strength had no change when jet-to-substrate distance was 1mm or 6mm. These results were corresponding to SEM and XPS results.

Keywords: PACS; 52.40.Hf; 81.05.Lg; 81.65.MqPolyamide 6 film; Atmospheric pressure plasma jet (APPJ); Etching rate; Influence; Distance

Assessment of interface roughness during plasma etching through the use of real-time ellipsometry by Chien-Yuan Han; Chien-Wen Lai; Yu-Faye Chao; Ke-Ciang Leou; Tsang-Lang Lin (pp. 2536-2539).

▶ Δ trajectory transitions were observed during plasma etching of SiO₂/Si interface. ▶ Roughness height analysis showed morphology of the etched interface was gradually changed. ▶ Transition periods of Δ have strongly relationship with roughness height of the etched interface.Real-time in situ ellipsometry was used to investigate the etching of SiO₂/silicon wafers with a high concentration of Cl₂. We monitored the temporal trajectory of the ellipsometric parameter Δ and then selected several points for ex situ study using atomic force microscopy (AFM). There was a clearly observable transition period in the trajectory near the endpoint of the SiO₂/Si interface. We studied the relationship between the ellipsometric parameter Δ and the same point in the AFM ex situ measurements. Three stages, thin film, the interface layer, and the substrate, were analyzed in this work.

Keywords: Ellipspometry; Surface roughness; Plasma etching; Real-time monitoring

Sliding friction and wear behaviors of surface-coated natural serpentine mineral powders as lubricant additive by Baosen Zhang; Yi Xu; Fei Gao; Peijing Shi; Binshi Xu; Yixiong Wu (pp. 2540-2549).

This paper is devoted to investigate the friction and wear properties of surface-coated natural serpentine powders (SP) as oil additive. The worn surface was characterized and the formation mechanism of the tribofilm was discussed accordingly. Results indicate that the optimal of additive concentration and applied load exist in the tests. A tribofilm, which is responsible for the decrease in friction and wear, mainly with iron oxides, silicon oxides, graphite and organic compounds was found on the worn surface.This work aims to investigate the friction and wear properties of surface-coated natural serpentine powders (SP) suspended in diesel engine oil using an Optimal SRV oscillating friction and wear tester. The worn surface was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). Results indicated that the additives can improve the wear resistance and decrease friction coefficient of carbon steel friction couples. The 0.5wt% content of serpentine powders is found most efficient in reducing friction and wear at the load of 50N. The SEM and XPS analysis results demonstrate that a tribofilm forms on the worn surface, which is responsible for the decrease in friction and wear, mainly with iron oxides, silicon oxides, graphite and organic compounds.

Keywords: Serpentine; Lubricant; Additive; Friction and wear

Effects of Ag addition on phase transformation and resistivity of TiSi₂ thin films by S.Y. Sun; C.J. Lee; H.S. Chou; J.C. Huang (pp. 2550-2554).

In this study, the effects of adding Ag to TiSi₂ thin films are examined. It is demonstrated that both the C49→C54 transformation temperature and the electric resistivity are appreciably lowered with Ag addition. Due to the presence of Ag nanocrystals precipitated at the C49 grain boundaries, the overall grain boundary density would increase to result in the higher nucleation rate of C54 and the lower transformation temperature. The precipitation of pure Ag network can provide another electric current conductive path except for the TiSi₂ grains. Due to the lower vacuum condition and the higher oxygen content in the current sputtered and annealed films, the C49→C54 transformation temperature and the resistivity of the TiSi₂–20at%Ag films can only be reduced by ∼100°C and 10μΩcm, as compared with the non-Ag additive films. With better fabrication vacuum, the transformation temperature and resistivity might be lowered to a level below 700°C and 15μΩcm, which are highly applausive for engineering applications.

Keywords: Silicide; Precipitation; Phase transformation; Resistivity

Niobium based coatings for dental implants by G. Ramírez; S.E. Rodil; H. Arzate; S. Muhl; J.J. Olaya (pp. 2555-2559).

▶ The coatings of niobium oxide and niobium nitride improve the corrosion resistance of stainless steel. ▶ The niobium oxide and niobium nitride coatings increase cell proliferation. ▶ The niobium-based coatings do not have a toxic effect on cells. ▶ The niobium nitride coatings show better cell adhesion than the uncoated stainless steel. ▶ The niobium-based coatings have a similar biocompatibility to titanium.Niobium based thin films were deposited on stainless steel (SS) substrates to evaluate them as possible biocompatible surfaces that might improve the biocompatibility and extend the life time of stainless steel dental implants. Niobium nitride and niobium oxide thin films were deposited by reactive unbalanced magnetron sputtering under standard deposition conditions without substrate bias or heating. The biocompatibility of the surfaces was evaluated by testing the cellular adhesion and viability/proliferation of human cementoblasts during different culture times, up to 7 days. The response of the films was compared to the bare substrate and pieces of Ti6Al4V; the most commonly used implant material for orthopedics and osteo-synthesis applications. The physicochemical properties of the films were evaluated by different means; X-ray diffraction, Rutherford backscattering spectroscopy and contact angle measurements. The results suggested that the niobium oxide films were amorphous and of stoichiometric Nb₂O₅ ( a-Nb₂O₅), while the niobium nitride films were crystalline in the FCC phase ( c-NbN) and were also stoichiometric with an Nb to N ratio of one. The biological evaluation showed that the biocompatibility of the SS could be improved by any of the two films, but neither was better than the Ti6Al4V alloy. On the other hand, comparing the two films, the c-NbN seemed to be a better surface than the oxide in terms of the adhesion and proliferation of human cemetoblasts.

Keywords: Biocompatibility; Niobium; Dental implants; Coatings; Corrosion

Study of electrical field distribution of gold-capped nanoparticle for excitation of localized surface plasmon resonance by Tatsuro Endo; Hikaru Takizawa; Yasunori Imai; Yasuko Yanagida; Takeshi Hatsuzawa (pp. 2560-2566).

The specific optical characteristics which can be observed from noble metal nanostructured materials such as nanoparticles and nanoislands have wide variety of applications such as biosensors, solar cells, and optical circuit. Because, these noble metal nanostructures induce the increment of light absorption efficiency by the enhancing effect of electrical field from localized surface plasmon resonance (LSPR) excitation. However, the enhancing effects of electrical field from LSPR using simple structured noble metal nanostructures for several applications are not satisfactory. To realize the more effective light absorption efficiency by the enhancing effect of electrical field, quite different noble metal nanostructures have been desired for applying to several applications using LSPR. In this study, to obtain the more effective enhancing effect of electrical field, conditions for LSPR excitation using a gold-capped nanoparticle layer substrate are computationally analyzed using finite-difference time-domain (FDTD) method. From the previous research, LSPR excitation using such gold-capped nanoparticle layer substrates has a great potential for application to high-sensitive label-free monitoring of biomolecular interactions. For understanding of detailed LSPR excitation mechanism, LSPR excitation conditions were investigated by analyzing the electrical field distribution using simulation software and comparing the results obtained with experimental results. As a result of computational analysis, LSPR excitation was found to depend on the particle alignment, interparticle distance, and excitation wavelength. Furthermore, the LSPR optical characteristics obtained from the simulation analysis were consistent with experimentally approximated LSPR optical characteristics. Using this gold-capped nanoparticle layer substrate, LSPR can be excited easily more than conventional noble metal nanoparticle-based LSPR excitation without noble metal nanoparticle synthesis. Hence, this structure is detectable a small change of refractive index such as biomolecular interactions for biosensing applications.

Keywords: Localized surface plasmon resonance (LSPR); Gold-capped nanoparticle; Finite-difference time-domain (FDTD) method; Electrical field distribution; Sensing application

Polyethylene welding by pulsed visible laser irradiation by L. Torrisi; F. Caridi; A.M. Visco; N. Campo (pp. 2567-2575).

▶ The polyethylene welding by using ns laser pulses is an important technique which permits to produce a mechanical resistant welded material.Laser welding of plastics is a relatively new process that induces locally a fast polymer heating. For most applications, the process involves directing a pulsed beam of visible light at the weld joint by going through one of the two parts. This is commonly referred to as “through transmission visible laser welding”. In this technique, the monochromatic visible light source uses a power ns pulsed laser in order to irradiate the joint through one part and the light is absorbed in the vicinity of the other part.In order to evaluate the mechanical resistance of the welded joint, mass quadrupole spectrometry, surface profilometry, microscopy techniques and mechanical shear tests were employed. The welding effect was investigated as a function of the laser irradiation time, nature of the polyethylene materials and temperature.

Keywords: Laser welding; Polyethylene; Absorption and transmission; Shear stress

Novel titration method for surface-functionalised silica by Kai Hofen; Siegfried Weber; Chiu Ping Candace Chan; Peter Majewski (pp. 2576-2580).

▶ Novel aqueous based titration method. ▶ Titration method successful for amine, sulphonate, and carboxyl groups. ▶ Titration results are affected by sample mass. ▶ Titration results are affected by diffusion of reactant.This paper describes three inexpensive and fast analytical methods to characterise grafted particle surfaces. The reaction of silica with (3-aminopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane and N-(phosphonomethyl)iminodiacetic acid hydrate, respectively, leads to NH₂-, SO₃H- or COOH-functionalised silica, which were characterised by X-ray photoelectron spectrometry and titration in nonaqueous media as well as with two titration methods in a water-based environment. In the work presented, factors influencing the titrations are pointed out and solutions are presented to overcome these limiting factors are shown.

Keywords: Functionalised silica; Titration

Investigation of fatigue failure prediction of Fe–Cr alloy coatings under rolling contact based on acoustic emission technique by Piao Zhong-yu; Xu Bin-shi; Wang Hai-dou; Pu Chun-huan (pp. 2581-2586).

▶ In this study, the acoustic emission (AE) method was used to investigate the failure predication of the plasma sprayed Fe–Cr alloy coatings under rolling contact. At the same time, the mechanism of the rolling contact fatigue (RCF) of the coatings was also discussed.The rolling contact fatigue (RCF) failure prediction of the coating Fe–Cr alloy coatings was investigated. The acoustic emission (AE) technique was used to monitor RCF tests of the coatings. The failure mechanism was investigated. Results showed AE signals sensitively detected the initiations and propagations of the fatigue cracks within the coatings before the obvious surface material losses. AE signals also reflected the cumulate damage procedure. So the coming RCF failures can be predicted by AE signal responses. Moreover, the micro-defects within the coatings were considered to be the fatigue crack origins.

Keywords: Plasma spraying; Acoustic emission; Rolling contact fatigue; Fracture mechanics; Life prediction

Preparation of superhydrophobic films on titanium as effective corrosion barriers by Fen Zhang; Shougang Chen; Lihua Dong; Yanhua Lei; Tao Liu; Yansheng Yin (pp. 2587-2591).

▶ The anodized surfaces exhibited special hierarchical structure. ▶ Superhydrophobic films were prepared by a simple immersion technique. ▶ Superhydrophobic film provides an effective corrosion resistant coating. ▶ The hierarchical structure with the low surface energy leads to surface superhydrophobicity.Stable superhydrophobic films were prepared on the electrochemical oxidized titania/titanium substrate by a simple immersion technique into a methanol solution of hydrolyzed 1 H,1 H,2 H,2 H-perfluorooctyltriethoxysilane [CF₃(CF₂)₅(CH₂)₂Si(OCH₂CH₃)₃, PTES] for 1h at room temperature followed by a short annealing at 140°C in air for 1h. The surface morphologies and chemical composition of the film were characterized by means of water contact angle (CA), field emission scanning electron microscopy (FESEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The water contact angle on the surface of this film was measured to be as high as 160°. SEM images showed that the resulting surfaces exhibited special hierarchical structure. The special hierarchical structure along with the low surface energy leads to the high surface superhydrophobicity. The corrosion resistance ability and durance property of the superhydrophobic film in 3.5wt.% NaCl solution was evaluated by the electrochemical impedance spectroscopy (EIS). The anticorrosion properties of the superhydrophobic film are compared to those of unmodified pure titanium and titania/titanium substrates. The results showed that the superhydrophobic film provides an effective corrosion resistant coating for the titanium metal even with immersion periods up to 90 d in the 3.5wt.% NaCl solution, pointing to promising future applications.

Keywords: Superhydrophobic film; Titania; Corrosion inhibition; EIS; Structure

Microstructure evolution of sol–gel HA films by D.G. Wang; C.Z. Chen; J. Ma; T. He (pp. 2592-2598).

Bioactive hydroxyapatite films were fabricated on titanium alloy by a sol–gel method. The samples were firstly precoated at a low drying temperature for many times and then calcined at a relative high temperature. The phase constitution, microstructure and composition analysis were studied by X-ray diffraction (XRD), electronic probe microanalysis (EPMA), and the microstructure evolution was explained by some schematic illustrations. When the samples were precoated only once, hexagonal structure is always observed. After the samples were precoated many times, the hexagonal structure can be preserved only when the drying temperature is 500°C or above. When the drying temperature is below 500°C, the dried layer easily redissolved into the next coated sol because of the existence of some water-soluble ions such as NO₃⁻, consequently the hexagonal structure disappeared and a coarse surface with some small pores formed. High calcining temperature can accelerate the atomic diffusion which may integrate the adjacent grains, but excessively high temperature such as 900°C or above would make the whole film be incinerated completely.

Keywords: Sol–gel; Microstructure; Hydroxyapatite; Film

Mixed-solvothermal synthesis of CdS micro/nanostructures and their optical properties by Shengliang Zhong; Linfei Zhang; Zhenzhong Huang; Shangping Wang (pp. 2599-2603).

Several novel cadmium sulfide (CdS) micro/nanostructures, including cauliflower-like microspheres, football-like microspheres, tower-like microrods, and dendrites were controllably prepared via an oxalic acid-assisted solvothermal route using ethylene glycol (EG) and H₂O as pure and mixed solvents with different S sources. The as-prepared products were characterized by X-ray powder diffraction (XRD), scanning electronic microscope (SEM) and UV–vis spectrophotometer (UV). It was found that CdS micro/nanostructures can be selectively obtained by varying the composition of solvent, concentration of oxalic acid, and sulfur sources. UV–vis absorption spectra reveal that their absorption properties are shape-dependent. The possible formation process of the CdS micro/nanostructures was briefly discussed. This route provides a facile way to tune the morphologies of CdS over a wide range.

Keywords: CdS; Solvothermal; Nanostructure

Ageing effects on the wettability behavior of laser textured silicon by B. Nunes; A.P. Serro; V. Oliveira; M.F. Montemor; E. Alves; B. Saramago; R. Colaço (pp. 2604-2609).

In the present work we investigate the ageing of acid cleaned femtosecond laser textured 〈100〉 silicon surfaces. Changes in the surface structure and chemistry were analysed by Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS), in order to explain the variation with time of the water contact angles of the laser textured surfaces. It is shown that highly hydrophobic silicon surfaces are obtained immediately after laser texturing and cleaning with acid solutions (water contact angle>120°). However these surfaces are not stable and ageing leads to a decrease of the water contact angle which reaches a value of 80°. XPS analysis of the surfaces shows that the growth of the native oxide layer is most probably responsible for this behavior.

Keywords: Silicon; Wettability; Laser texturing; Surface chemistry; Acid-treatment; Ageing

Wear resistance of reactive plasma sprayed and laser remelted TiB₂–TiC_0.3N_0.7 based composite coatings against medium carbon steel by Zhengping Mao; Jun Wang; Baode Sun; Rajendra K. Bordia (pp. 2610-2616).

▶ The wear mechanism of as-sprayed coating at low sliding speed is grain abrasion. ▶ It changes to fatigue failure at higher sliding speed. ▶ The wear resistance of laser treated coatings is better than as-sprayed coatings. ▶ The dominant wear mechanism of laser treated coatings is oxidation.Wear resistance of reactive plasma sprayed TiB₂–TiC_0.3N_0.7 based composite coatings and the as-sprayed coating with laser surface treatment was investigated using plate-on-plate tests. Wear tests were performed at different normal loads and sliding speeds under dry sliding conditions in air. The surface morphologies of counterparts against as-sprayed and laser remelted coatings were investigated. The microstructure and chemical composition of wear debris and coatings were studied using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The results show that the wear resistance of the laser remelted coating is improved significantly due to their increased microhardness and reduced flaws. The primary wear mechanism of the remelted coating is oxidation wear and its minor wear mechanisms are grain abrasion and fatigue failure during the course of wear test. In contrast, the primary wear mechanism of the as-sprayed coating is grain abrasion at the low sliding speed (370rpm) and fatigue failure at the high sliding speed (549rpm). The oxidation wear mechanism is a minor contributor for the as-sprayed coating.

Keywords: Reactive plasma spraying; Laser surface treatment; Composite coating; Wear resistance; Wear mechanism

Preparation of ceramic coating on Ti substrate by Plasma electrolytic oxidation in different electrolytes and evaluation of its corrosion resistance by M. Shokouhfar; C. Dehghanian; A. Baradaran (pp. 2617-2624).

Ceramic oxide coatings (titania) were produced on Ti by micro-arc oxidation in different aluminate and carbonate based electrolytes. This process was conducted under constant pulsed DC voltage condition. The effect of KOH and NaF in aluminate based solution was also studied. The surface morphology, growth and phase composition of coatings were investigated using scanning electron microscope and X-ray diffraction. Corrosion behavior of the coatings was also examined by potentiodynamic polarization and electrochemical impedance spectroscopy. It was found that the sparking initiation voltage (spark voltage) had a significant effect on the form and properties of coatings. Coatings obtained from potassium aluminate based solution had a lower spark voltage, higher surface homogeneity and a better corrosion resistance than the carbonate based solution. Addition of NaF instead of KOH had improper effects on the homogeneity and adhesion of coatings which in turn caused a poor corrosion protection behavior of the oxide layer. AC impedance curves showed two time constants which is an indication of the coatings with an outer porous layer and an inner compact layer.

Keywords: Plasma electrolytic oxidation; Ceramic coatings; Growth characteristics; Titanium alloy; Corrosion resistance

Morphological control of copper phthalocyanine films by protonation-electrophoretic deposition by Yuanyuan Zhu; Lingfeng Qian; Minzhao Xue; Qiaorong Sheng; Qing Zhang; Yangang Liu (pp. 2625-2632).

Films composed of various nanostructured copper phthalocyanine are controllably prepared by the method of protonation-electrophoretic deposition. The ultralong nanowires of copper phthalocyanine are grown at the deposition temperature of 70°C. And the results of films UV–vis absorption spectra and X-ray diffraction indicate that copper phthalocyanine possesses the transformation tendency from α-phase to thermostable β-phase under the higher deposition temperature. The formation process of the ultralong nanowires illustrates that the nanowires grow in longitudinal orientation much faster than in lateral direction. And the time dependence of the films morphology, from another point of view, proves that copper phthalocyanine is dissolved in the precursor solutions, and the formation of the nanostructured copper phthalocyanine contains the process of crystal growth, which is different from the traditional electrophoretic deposition. So the films morphology is flexible to be controlled by varying the deposition conditions. These diverse nanostructured films have potential applications in the electrochemical and optoelectrical equipments.

Keywords: Copper phthalocyanine; Electrophoretic deposition; Ultralong nanowires

Adsorption of CO, NH₃ and O₂ on Fe site of La_0.875Sr_0.125FeO₃ (010) surface by density function theory calculation by Lihui Sun; Hongwei Qin; Feng Gao; Ensi Cao; Kai Fan; Jifan Hu (pp. 2633-2636).

▶ The C-down configuration is stable for the CO adsorption. ▶ The N-down configuration is more stable than the H-down one for NH₃ adsorption. ▶ The mode with an angle of about 120° between the O₂ and surface is stable.The adsorption of CO, NH₃ and O₂ gas molecules on Fe site of La_0.875Sr_0.125FeO₃ (010) surface has been investigated based on the density functional theory (DFT) with the spin polarized generalized gradient approximation (GGA). The optimal adsorption orientations as well as the adsorption energies for these molecules adsorption on Fe site of La_0.875Sr_0.125FeO₃ (010) surface are derived. Results show that adsorption configurations with C-down for CO, N-down for NH₃ are stable. For the O₂ molecule adsorption, the mode with an angle about 120° between the oxygen molecule and La_0.875Sr_0.125FeO₃ (010) surface is stable.

Keywords: Density functional theory (DFT); Sr doped; Adsorption energy; Charge transfer

Microwave-assisted covalent modification of graphene nanosheets with chitosan and its electrorheological characteristics by Huating Hu; Xianbao Wang; Jingchao Wang; Fangming Liu; Min Zhang; Chunhui Xu (pp. 2637-2642).

▶ Microwave-assisted covalent modification of graphene nanosheets with chitosan. ▶ The GNS–CS nanocomposites dispersed well in aqueous acetic acid. ▶ The GNS–CS nanocomposites with excellent biocompatibility and bioactivity.Biofunctionalization and manipulating of graphene nanosheets (GNS) are important for biomedical research and application. Chitosan (CS) modified graphene nanosheets have been successfully prepared under microwave irradiation in N,N-dimethylformamide medium, which involved the reaction between the carboxyl groups of graphene oxide nanosheets (GONS) and the amido groups of chitosan followed by the reduction of graphene oxide nanosheets into graphene nanosheets using hydrazine hydrate. The as-prepared graphene nanosheets–chitosan (GNS–CS) nanocomposites have been characterized by FTIR, TEM, FESEM, XRD and TG. The results showed that chitosan was covalently grafted onto the surface of graphene nanosheets via amido bonds. Solubility measurements indicated that the resultant nanocomposites dispersed well in aqueous acetic acid. Especially, the electrorheological (ER) properties of the GNS–CS nanocomposites have been investigated. It is believed that this new nanocomposites may be promising for biomedical applications.

Keywords: Graphene; Chitosan; Microwave; Electrorheological property

Non-hysteretic metal–insulator transition of VO₂ films grown by excimer-laser-assisted metal organic deposition process by Masami Nishikawa; Tomohiko Nakajima; Toshiya Kumagai; Takeshi Okutani; Tetsuo Tsuchiya (pp. 2643-2646).

We examined the correlation between thickness of an epitaxial VO₂ phase grown on a TiO₂ (001) substrate by the excimer-laser-assisted metal organic deposition (ELAMOD) process and the metal–insulator transition (MIT) property of it. The abrupt and hysteretic MIT was observed for the epitaxial films (thickness: t≥6nm), and the epitaxial film ( t≤4nm) showed semiconductor behavior. When an amorphous VO_x layer was prepared on the ultrathin epitaxial phase ( t≤4nm) by the ELAMOD, a non-hysteretic MIT was successfully observed. The non-hysteretic MIT was found to be owing to roughened interface between the epitaxial phase and the amorphous phase, where there would be a number of structural defects.

Keywords: VO; ₂; Epitaxial film; Metal–insulator transition; Hysteresis; Excimer laser

Nanoporous nickel oxide thin films and its improved electrochromic performance: Effect of thickness by D.S. Dalavi; M.J. Suryavanshi; D.S. Patil; S.S. Mali; A.V. Moholkar; S.S. Kalagi; S.A. Vanalkar; S.R. Kang; J.H. Kim; P.S. Patil (pp. 2647-2656).

▶ Present paper demonstrate the electrochromic properties (EC) of NiO thin films of different thickness with change in deposition time by a simple and cost effective chemical bath deposition method. ▶ Nanoporous NiO thin films were investigated as a function of film thickness in both aqueous (KOH) and non aqueous (LiClO₄-PC) electrolyte. ▶ The increment in the transmittance modulations with increase in film thickness leads to an increase in coloration efficiency (CE) to about 95cm²/C, which is two times more than that observed in KOH with excellent electrochemical stability upto 3000c/b cycles in LiClO₄-PC electrolyte. ▶ This suggest that electrochromic properties of the NiO films can be tailored merely by controlling the film thickness and choice of suitable electrolyte which will be potentially useful for designing complementary EC devices.Electrochromic properties of chemically bath deposited nanoporous NiO thin films were investigated as a function of film thickness using Ni sulphate precursor, aqueous ammonia and potassium persulphate as complexing and oxidizing agents respectively. The films were characterized for their structural, morphological, optical and electrochromic properties using X-ray diffraction, scanning electron microscopy, FT-IR spectroscopy, cyclic voltammetry, chronoamperometry and optical transmittance studies. X-ray diffraction patterns show that the films are polycrystalline, consisting of NiO cubic phase. Infrared spectroscopy results show the presence of free hydroxyl ion and water in NiO thin films. SEM micrographs revealed nanoporous nature composed of interconnected nanoporous network, forming well defined 3D nano envelopes. The optical band gap energy was found to be decreased from 3.22 to 2.80eV with increasing film thickness. The electrochromic properties of all the films were investigated in aqueous (KOH) and non aqueous (LiClO₄-PC) electrolyte by means of cyclic voltammetry (CV), chronocoulometry (CC) and optical studies. The transmittance modulations or optical density differences during the coloring/bleaching process were found to be increased with the film thickness. This increment in optical differences led to an increase in coloration efficiency (CE) to about 95cm²/C, which is two times more than that observed in KOH and response time of 2.9s for bleaching (reduction) and 3.5s for coloration (oxidation) observed for the film deposited at 60min with excellent electrochemical stability up to 3000 c/b cycles in LiClO₄-PC electrolyte.

Keywords: NiO thin films; Chemical bath deposition (CBD); Scanning electron microscopy; Electrochromic properties; CV; CA

Mechanical and corrosion resistance of hydrophilic sphene/titania composite coatings on titanium and deposition and release of cefazolin sodium/chitosan films by Su Cheng; Daqing Wei; Yu Zhou (pp. 2657-2664).

The mechanical and corrosion resistance of hydrophilic sphene/titania composite coatings on titanium formed by a hybid technique of microarc oxidation (MAO) and heat-treatment were investigated. The results indicated that the heat-treatment could improve the hardness, elastic modulus, elastic recovery and corrosion resistance of the MAO coatings, and reinforce the interface bonding between MAO coatings and titanium. A cefazolin sodium/chitosan drug film was prepared on the coating surfaces. The drug load procedures such as the addition of chitosan obviously increased the sustained-release ability of drug films. In addition, the increase of cefazolin sodium concentration could increase the accumulative release concentration of cefazolin sodium. The sustaining-release ability of drug films deposited on the MAO and heat-treated MAO coatings is similar. In the interior of drug film, the physical and chemical bonding reactions such as Coulombic interactions, van der Waals force and H-bonding etc. could be produced, through the chemical group interactions such as –OH and –NH₂ groups of chitosan with –CO of cefazolin sodium.

Keywords: Titanium; Sphene; Cefazolin sodium; Chitosan; Microarc oxidation; Heat-treatment

Chemical and morphological difference between TiN/DLC and a-C:H/DLC grown by pulsed vacuum arc techniques by H.A. Castillo; E. Restrepo-Parra; P.J. Arango-Arango (pp. 2665-2668).

▶ Morfhological properties of DLC coatings are strongly influenced by the interlayer. ▶ Deposition parameters influence the DLC coatings behaviour. ▶ The interlayer type do not produce a visible influence the vibrational energies of DLC coatings.In order to improve the adherence of DLC films, interlayers of amorphous hydrogenated carbon (a-C:H) and titanium nitride (TiN) were deposited by means of the pulsed vacuum arc technique. Bilayers were obtained by using a carbon target of 99.98% of purity in mixtures of (Ar+CH₄) and (Ar+H₂) for producing a-C and DLC, respectively and a target of titanium of 99.999% in a mixture of (Ar+N₂) for growing TiN. After the deposition, chemical and morphological differences between TiN/DLC and a-C:H/DLC bilayers grown on silicon and stainless steel 304 were studied using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and scanning probe microscopy (SPM) techniques. XPS analysis showed a difference in sp³/(sp²+sp³) bonds ratio for each bilayer, being 0.67 for TiN/DLC and 0.45 for a-C:H/DLC bilayers. sp³ and sp² bonds were also observed by the FTIR technique. SPM images, in atomic force microscopy (AFM) and lateral force microscopy (LFM) modes were carried out for illustrating the comparison between TiN/DLC and a-C/DLC morphologic characteristics. Roughness and grain size were studied as a function of the H₂ concentration for both bilayers.

Keywords: TiN/DLC; a-C/DLC; Pulsed arc; Adherence; Morphology; XPS

Temperature and magnetic field responsive hyaluronic acid particles with tunable physical and chemical properties by Sema Ekici; Pinar Ilgin; Selahattin Yilmaz; Nahit Aktas; Nurettin Sahiner (pp. 2669-2676).

We report the preparation and characterization of thiolated-temperature-responsive hyaluronic acid–cysteamine–N-isopropyl acrylamide (HA–CYs–NIPAm) particles and thiolated-magnetic-responsive hyaluronic acid (HA–Fe–CYs) particles. Linear hyaluronic acid (HA) crosslinked with divinyl sulfone as HA particles was prepared using a water-in-oil micro emulsion system which were then oxidized HA–O with NaIO₄ to develop aldehyde groups on the particle surface_. HA–O hydrogel particles were then reacted with cysteamine (CYs) which interacted with aldehydes on the HA surface to form HA particles with cysteamine (HA–CYs) functionality on the surface. HA–CYs particles were further exposed to radical polymerization with NIPAm to obtain temperature responsive HA–CYs–NIPAm hydrogel particles. To acquire magnetic field responsive HA composites, magnetic iron particles were included in HA to form HA–Fe during HA particle preparation. HA–Fe hydrogel particles were also chemically modified. The prepared HA–CYs–NIPAm demonstrated temperature dependent size variations and phase transition temperature. HA–CYs–NIPAm and HA–Fe–CYs particles can be used as drug delivery vehicles. Sulfamethoxazole (SMZ), an antibacterial drug, was used as a model drug for temperature-induced release studies from these particles.

Keywords: Temperature-sensitive HA particles; Magnetic composite; Drug release; Modifiable HA particles

Effect of stearic acid, zinc stearate coating on the properties of synthetic hydromagnesite by Hongchang Han; Shan Hu; Jinqing Feng; Huliang Gao (pp. 2677-2682).

▶ Surface of the synthetic hydromagnesite was changed from hydrophilic to lipophilic. ▶ The flowability of the surface modified synthetic hydromagnesite was improved. ▶ The surface modifiers and the modifying processing did not affect the crystal structure. ▶ The surface modifier had no obvious influence on the powder's degradation pathway.Synthetic hydromagnesite (SHM), used as flame retardant for polymers, may have similar or better flame retardancy effectiveness than aluminum tri-hydroxide (ATH) and magnesium di-hydroxide (MDH). Suitable surface modifiers are often employed to improve its dispersion and compatibility with polymer matrix. In this study, we chose stearic acid (SA) and zinc stearate (ZS) as the surface modifier, and investigated the properties of SHM modified with various surface modifier content using dry blending coating process. Scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG), particle size distribution, contact angle, oil absorption, bulk density, tapped density and Carr's index were employed to characterize the effect of surface modification. The results showed that the surface of SHM powders was changed from hydrophilic to lipophilic. The flowability of the surface modified powder was also improved. TG graphs showed that the surface modifier had no obvious influence on the degradation pathway of the SHM.

Keywords: Synthetic hydromagnesite; Stearic acid; Zinc stearate; Surface modification

Ti/TiN multilayer thin films deposited by pulse biased arc ion plating by Yanhui Zhao; Guoqiang Lin; Jinquan Xiao; Hao Du; Chuang Dong; Lijun Gao (pp. 2683-2688).

▶ Ti/TiN multilayer films were successfully deposited by pulse biased arc ion plating. ▶ The highest hardness value reached 43GPa for the modulation period of 54nm. ▶ A good adhesion of the deposited films is achieved with a maximum adhesion of 83N. ▶ Such superhard multilayer films would be favorable for application in the future.In this work, the effect of modulation period ( Λ) on Ti/TiN multilayer films deposited on high-speed-steel (HSS) substrates using pulse biased arc ion plating is reported. The crystallography structures and cross-sectional morphology of Ti/TiN multilayer films were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM), respectively. Their mechanical properties were determined via nanoindentation measurements, while the film/substrate adhesion via the scratch test. It was found that the highest hardness value reached 43GPa for the modulation period of 54nm, while the film/substrate adhesion also reached the highest value of 83N. Furthermore, the hardness enhancement mechanism in the multilayer films is discussed.

Keywords: Multilayer films; Pulse biased arc ion plating; Hardness; Adhesion

Properties of barium hexa-ferrite thin films dependent on sputtering pressure by Huizhong Xu; Wenxu Zhang; Bin Peng; Wanli Zhang (pp. 2689-2693).

▶ In magnetron sputtering of barium ferrite thin films, the sputtering pressure can. ▶ Tune the composition of the film and also the growth rate of the film. ▶ Inhibit the formation of needle like grains. ▶ Influence of the morphologies, texture and magnetic properties significantly.M-type barium ferrite thin films were deposited onto sapphire (00 l) substrates by radio frequency magnetron sputtering. An ultra-thin layer about 20nm was deposited and annealed before continuous deposition of the films up to 500nm under different sputtering pressures: 0.2, 0.5, 0.8 and 1.0Pa, respectively. It was found that the atomic ratios of Fe to Ba increased from 9.3 to 15.0 with the increase of the pressure. The films sputtered at all pressures have c-axis normal to the film plane by a four circle X-ray diffractometer, which is an improvement of the films directly sputtered on the substrate. Needle-like grains were formed on the surface of the films under higher sputter pressure with bubble domains, which is originated from high magnetocrystalline anisotropy of the film. Magnetic hysteresis loops recorded by vibrating sample magnetometer agree with them, where in-plane and out-of-plane loops of the samples prepared under high sputtering pressures are quite different, while they are almost identical of the samples under low pressures. The influence of the sputtering pressure was understood by that with the increase of the pressure, resputtering of the films was increased. Nucleation with c-axis normal to the film plane was deteriorated. Thus samples prepared under high pressure have more needle-like crystallites which have c-axis parallel to the film plane.

Keywords: Barium hexa-ferrites; Textures; Thin films; Magnetron sputtering

Influence of standoff distance on the structure and properties of carbon coatings deposited by atmospheric plasma jet by L. Marcinauskas; M. Silinskas; A. Grigonis (pp. 2694-2699).

▶ Carbon coatings (standoff distance 5mm) are porous with ∼10GPa hardness. ▶ Coatings (standoff distance >5mm) are softer with high H (∼25at.%) and O content. ▶ Decrease of standoff distance yields lower H (7at.%) and O (5at.%) concentration. ▶ H is mainly bonded to the sp³ carbon (70–60at.%) and forms methylene compounds.Carbon coatings were deposited by atmospheric plasma jet. Influence of the distance between the exit of the plasma gun and a substrate (consequently temperature of the substrate) on properties of the coatings was investigated. The coatings deposited near to the exit of the plasma gun are porous with columnar structure, moderate hardness (∼10GPa), and the lowest hydrogen (∼7at.%) concentration. The coatings deposited at the larger standoff distance (>5mm) have higher hydrogen (≤25at.%) content and graphite-like structure. Most of the hydrogen in all coatings is bonded to the sp³ carbon (70–60at.%) and predominantly forms methylene compounds. Decrease of standoff distance yields lower concentration of sp³ CH₃ compounds and relative increase of amount of hydrogenated sp² rings.

Keywords: Plasma jet deposition; Acetylene; Amorphous hydrogenated carbon; Raman spectroscopy; IR spectroscopy; Hydrogen

Optimization of inductively coupled plasma deep etching of GaN and etching damage analysis by Rongfu Qiu; Hai Lu; Dunjun Chen; Rong Zhang; Youdou Zheng (pp. 2700-2706).

▶ Inductively coupled plasma (ICP) deep etching of GaN is systemically studied by varying ICP power, RF power and chamber pressure, respectively. ▶ The quality of the etched GaN surface is found to be largely dependent on the RF power applied while the ICP power and chamber pressure play a relatively minor role. ▶ Sub-micrometer-scale hexagonal pits and pillars originating from part of the structural defects within the original GaN layer are observed on the etched surface. ▶ Considerable reduction of PL band-edge emission from the etched GaN surface indicates that high-density non-radiative recombination centers are created by ICP etching. ▶ A low-surface-damage etch recipe with high ICP power, low RF power, high chamber pressure is suggested.Inductively coupled plasma (ICP) etching of GaN with an etching depth up to 4μm is systemically studied by varying ICP power, RF power and chamber pressure, respectively, which results in etch rates ranging from ∼370nm/min to 900nm/min. The surface morphology and damages of the etched surface are characterized by optical microscope, scanning electron microscope, atomic force microscopy, cathodoluminescence mapping and photoluminescence (PL) spectroscopy. Sub-micrometer-scale hexagonal pits and pillars originating from part of the structural defects within the original GaN layer are observed on the etched surface. The density of these surface features varies with etching conditions. Considerable reduction of PL band-edge emission from the etched GaN surface indicates that high-density non-radiative recombination centers are created by ICP etching. The density of these non-radiative recombination centers is found largely dependent on the degree of physical bombardments, which is a strong function of the RF power applied. Finally, a low-surface-damage etch recipe with high ICP power, low RF power, high chamber pressure is suggested.

Keywords: GaN; ICP etching; Defects

In-situ study of the diffusion-reaction mechanism in Mo/Si multilayered films by S. Bruijn; R.W.E. van de Kruijs; A.E. Yakshin; F. Bijkerk (pp. 2707-2711).

▶ Diffusion in multilayers can be monitored in situ by measuring the period over time. ▶ Interface growth in Mo/Si multilayers obeys parabolic growth law after 10–50h. ▶ The diffusion coefficients in the diffusion controlled regime obey Arrhenius law.We present a low temperature diffusion study on the formation of intermixing zones between periodic, nanometer thick films consisting of Mo and Si. An in-situ X-ray diffraction method at pm-accuracy was developed, including a model that explains the period change observed by diffusion limited interface growth. Experiments were carried out on Mo/Si multilayered films in the temperature range of 100–275°C, resulting in the determination of diffusion coefficients. Temperature scaling showed Arrhenius-type behavior of the diffusion constant over the entire temperature range, with an activation energy of 0.5eV.

Keywords: Diffusion; Thin films; Multilayers; MoSi; ₂; Interface; X-ray diffraction; Molybdenum; Silicon

Surface derivatization with spacer molecules on glutaraldehyde-activated amino-microplates for covalent immobilization of β-glucosidase by Yaodong Zhang; Yun Zhang; Juanjuan Jiang; Li Li; Caihong Yu; Tingting Hei (pp. 2712-2716).

▶ Use spacer molecular for surface derivatization of amino-microplates. ▶ Generate sufficient spacing on polystyrene microplate surfaces for binding. ▶ Preserve the reactivity of immobilized biomolecule.Protein molecules immobilized on a hydrophobic polystyrene microplate by passive adsorption lose their activity and suffer considerable denaturation. In this paper, we report a thorough evaluation of a protocol for enzyme immobilization on a microplate with relatively inexpensive reagents, involving glutaraldehyde coupling and spacer molecules, and employing β-glucosidase as a model enzyme. The recommended conditions for the developed method include 2.5% glutaraldehyde to activate the reaction, 1% chitosan in an HAc solution to increase the binding capacity, 2% bovine serum albumin to block non-specific binding sites, and 0.1M NaBH₄ to stabilize Schiff's base intermediates. Using this method, the amount of β-glucosidase immobilized on amino-microplate was 24-fold with chitosan than without spacer molecules. The procedure is efficient and quite simple, and may thus have potential applications in biosensing and bioreactor systems.

Keywords: Protein immobilization; Microplate; β-Glucosidase; Spacer molecule

Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni by Mark C. Biesinger; Brad P. Payne; Andrew P. Grosvenor; Leo W.M. Lau; Andrea R. Gerson; Roger St.C. Smart (pp. 2717-2730).

▶ Practical approach to deconvolution of complex X-ray photoelectron 2 p spectra of Cr, Mn, Fe, Co and Ni species. ▶ Full disclosure of peak-fitting parameters presented as these are needed to reproduce fitting procedures. ▶ Comparison to quality standard samples provides best opportunity to understand species present. ▶ This approach takes into account peak asymmetries, multiplet splitting, shake-up and plasmon structures. ▶ A significant improvement over single peak binding energies used by databases for these species.Chemical state X-ray photoelectron spectroscopic analysis of first row transition metals and their oxides and hydroxides is challenging due to the complexity of their 2p spectra resulting from peak asymmetries, complex multiplet splitting, shake-up and plasmon loss structure, and uncertain, overlapping binding energies. Our previous paper [M.C. Biesinger et al., Appl. Surf. Sci. 257 (2010) 887–898.] in which we examined Sc, Ti, V, Cu and Zn species, has shown that all the values of the spectral fitting parameters for each specific species, i.e. binding energy (eV), full wide at half maximum (FWHM) value (eV) for each pass energy, spin–orbit splitting values and asymmetric peak shape fitting parameters, are not all normally provided in the literature and data bases, and are necessary for reproducible, quantitative chemical state analysis. A more consistent, practical and effective approach to curve fitting was developed based on a combination of (1) standard spectra from quality reference samples, (2) a survey of appropriate literature databases and/or a compilation of literature references and (3) specific literature references where fitting procedures are available. This paper extends this approach to the chemical states of Cr, Mn, Fe, Co and Ni metals, and various oxides and hydroxides where intense, complex multiplet splitting in many of the chemical states of these elements poses unique difficulties for chemical state analysis. The curve fitting procedures proposed use the same criteria as proposed previously but with the additional complexity of fitting of multiplet split spectra which has been done based on spectra of numerous reference materials and theoretical XPS modeling of these transition metal species. Binding energies, FWHM values, asymmetric peak shape fitting parameters, multiplet peak separation and peak area percentages are presented. The procedures developed can be utilized to remove uncertainties in the analysis of surface states in nano-particles, corrosion, catalysis and surface-engineered materials.

Keywords: X-ray photoelectron spectroscopy; Transition metals; Chemical states; Peak fitting

Effects of deposition temperatures and annealing conditions on the microstructural, electrical and optical properties of polycrystalline Al-doped ZnO thin films by Joon-Ho Oh; Kyoung-Kook Kim; Tae-Yeon Seong (pp. 2731-2736).

▶ Rapid-thermal-annealing results in larger grains compared to furnace-annealing ▶ Rapid-thermal-annealed samples show low carrier concentrations and high mobilities ▶ Furnace-annealed samples produce higher carrier concentrations and moderate mobilities ▶ Optical bandgap of annealed samples increases with increasing carrier concentrationAl-doped ZnO (AZO, ZnO:Al₂O₃=98:2wt%) films are deposited on different substrates by an RF magnetron sputtering and subsequently annealed at three different conditions to investigate the microstructural, electrical, and optical properties. X-ray diffraction and scanning electron microscope results show that all the samples are polycrystalline and the samples rapid-thermal-annealed at 900°C in an N₂ ambient contain larger grains compared to the furnace-annealed samples. It is shown that the sample deposited at room temperature on the sapphire gives a resistivity of 5.57×10⁻⁴Ωcm when furnace-annealed at 500°C in a mixture of N₂:H₂ (9:1). It is also shown that the Hall mobility vs. carrier concentration ( μ– n) relation is divided into two groups, depending on the annealing conditions, namely, either rapid-thermal annealing or furnace annealing. The relations are described in terms of either grain boundary scattering or ionized impurity scattering mechanism. In addition, the samples produce fairly high transmittance of 91–96.99% across the wavelength region of 400–1100nm. The optical bandgaps of the samples increase with increasing carrier concentration.

Keywords: Transparent conducting oxide; Al-doped ZnO film; Annealing condition; RF magnetron sputtering

Influence of the microstructure on the corrosion behaviour of a shape memory Cu–Al–Be alloy in a marine environment by S. Montecinos; S.N. Simison (pp. 2737-2744).

▶ Chloride environment can produce a dealuminization attack. ▶ The corrosion behaviour is affected by the microstructure of the samples. ▶ In the (β+γ₂) microstructure, preferential dissolution of precipitates occurs. ▶ The presence of γ₂ precipitates seems to protect β matrix from dealloying.The influence of the microstructure on the corrosion behaviour of a shape memory Cu–11.40Al–0.55Be (wt.%) polycrystalline alloy in 3.5% NaCl has been studied by microscopical examinations, spectroscopical and X-ray diffraction measurements, and electrochemical tests. Chloride environment can produce a dealuminization attack, and the corrosion behaviour is affected by the alloy microstructural conditions. After long times of immersion, the single β phase microstructure suffers localized corrosion in some regions but dealuminization is generalized on the whole surface. However, in the (β+γ₂) microstructure, preferential dissolution of γ₂ dendritic precipitates occurs, which seems to protect β matrix from dealloying.

Keywords: Copper-based alloys; Corrosion; Microstructure; Shape memory alloys

Cadmium (II) pyrrolidine dithiocarbamate complex as single source precursor for the preparation of CdS nanocrystals by microwave irradiation and conventional heating process by R. Marx Nirmal; K. Pandian; K. Sivakumar (pp. 2745-2751).

▶ A controllable and rapid approach to synthesise CdS nanocrystals by using a new single source molecular precursor cadmium pyrrolidine dithiocarbamate Cd(pdtc)₂. ▶ The synthesis of CdS nanocrystals is achieved by thermal decomposition of cadmium (II) pyrrolidine dithiocarbamate (Cd(pdtc)₂) complex with hexadecylamine under conventional heating and microwave irradiation. ▶ In microwave irradiation, the monodispersed CdS nanoparticles were obtained whereas the nanorods were formed by conventional heating process. ▶ A comparison of the formation of different shapes and sized CdS prepared by both thermal decomposition and microwave irradiation and their structural and optical characterizations are presented. ▶ This novel method was expected to produce various semiconductor nanocrystals with high yield and purity.The complex of cadmium with pyrrolidine dithiocarbamate Cd(pdtc)₂ has been used as single source precursor for the synthesis of CdS nanoparticles. The formation of CdS nanostructures was achieved by thermal decomposition of the complex under microwave irradiation and conventional heating in presence of hexadecylamine. The CdS nanoparticles with disordered close-packed structure were obtained under microwave irradiation, whereas wurtzite hexagonal phase CdS nanorods were obtained by conventional heating method (up to 150°C). Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and high resolution transmission electron microscopy (HRTEM) studies also were carried out to study the structure and morphology of nanoparticles. The optical property of the CdS nanoparticles was studied by UV–visible and fluorescence emission spectral studies. Fluorescence measurements on the CdS nanoparticles show a strong emission spectrum with two sub bands that are attributed to band-edge and surface-defect emissions. The reduction of a suitable cadmium metal complex is considered to be one of the single pot methods to generate CdS semiconductor nanoparticles with different shapes and high yield.

Keywords: Semiconductors; Chemical synthesis; Electron microscopy (TEM and SEM); Optical properties

Conciliating surface superhydrophobicities and mechanical strength of porous silicon films by Fuguo Wang; Kun Zhao; Jinchun Cheng; Junyan Zhang (pp. 2752-2755).

Hydrophobic surfaces on Mechanical stable macroporous silicon films were prepared by electrochemical etching with subsequent octadecyltrichlorosilane (OTS) modification. The surface morphologies were controlled by current densities and the mechanical properties were adjusted by their corresponding porosities. Contrast with the smooth macroporous silicon films with lower porosities (34.1%) and microporous silicon with higher porosities (97%), the macroporous film with a rough three-dimension (3D) surface and a moderate pore to cross-section area ratio (37.8%, PSi2′) exhibited both good mechanical strength (Yong’ modulus, shear modulus and collapse strength are 64.2, 24.1 and 0.32GPa, respectively) and surface superhydrophobicity (water contact angle is 158.4±2° and sliding angle is 2.7±1°). This result revealed that the surface hydrophobicities (or the surface roughness) and mechanical strength of porous films could be conciliated by pore to cross-section area ratios control and 3D structures construction. Thus, the superhydrophobic surfaces on mechanical stable porous films could be obtained by 3D structures fabrication on porous film with proper pore to cross-section area ratios.

Keywords: Superhydrophobic surfaces; Porous silicon; Mechanical properties

Surface modification of gold nanoparticles and their monolayer behavior at the air/water interface by Chaio-Ling Hsu; Ke-Hsuan Wang; Chien-Hsiang Chang; Wen-Ping Hsu; Yuh-Lang Lee (pp. 2756-2763).

Schematic illustration showing the adsorption of a cationic surfactant on a MSA-modified Au particle and its behavior at the air/water interface.Display Omitted▶ MSA renders an Au surface with carboxylic groups. ▶ Carboxylic groups react with a cationic surfactant. ▶ Desorption of surfactant into water results in a hydrophilic region.Gold nanoparticles were prepared by two different methods. The first method was chemically grafting the particles with different lengths of alkylthiol (C₆SH, C₁₂SH and C₁₈SH). For the second method, the Au particles were surface modified first by mercaptosuccinic acid (MSA) to render a surface with carboxylic acid groups which play a role to physically adsorb cationic surfactant in chloroform. This method was termed physical/chemical method. In the first method, the effects of alkyl chain length and dispersion solvent on the monolayer behavior of surface modified gold nanoparticles was evaluated. The gold nanoparticles prepared by 1-hexanthiol demonstrated the narrowest size distribution. Most of them showed narrower particle size distributions in chloroform than in hexane. For the physical/chemical method, the particles can spread more uniformly on the water surface which is attributed to the amphiphilic character of the particles at the air/water interface. However, the particles cannot pack closely due to the relatively weak particle–particle interaction. The effect of alkyl chain length was also assessed for the second method.

Keywords: Surface modification; Gold nanoparticles; Monolayer

Luminescence characteristics of Ca1−_xSr_xS:Ce nanophosphors by Geeta Sharma; Ankush Vij; S.P. Lochab; Nafa Singh (pp. 2764-2768).

Luminescence characteristics of Ca1−_xSr_xS:Ce ( x=0, 0.25, 0.50, 1) nanophosphors have been investigated. XRD of all the samples show a single cubic phase of Ca1−_xSr_xS:Ce. TEM micrographs exhibit the rod like structure of the samples with a decrease in diameter with decreasing amount of Ca. The results of TEM were found to be in good agreement with the XRD results. The photoluminescence spectrum comprises of a main peak in the range 480–510nm with a shoulder in the range 530–565nm, which may be ascribed to transitions from 5d–4f levels of cerium in the mixed host lattice. The red shift in the emission wavelength with increasing Ca content may be correlated with the change in crystal field of mixed host lattice for different Ca and Sr concentrations. We have also investigated TL response of Ca1−_xSr_x:Ce to⁶⁰Co-γ rays. All the samples with different Sr and Ca contents show different TL response. TL response for the sample with x=0.75 shows the simplest TL glow curve with the maximum TL intensity, for which we have calculated the activation energy using glow curve deconvolution functions.

Keywords: Photoluminescence; Thermoluminescence; Mixed lattice; Nanophosphors

Effect of oxidation temperature on microstructure, mechanical behaviors and surface morphology of nanocomposite Ti–C_x–N_y thin films by Y.H. Lu; J.P. Wang; Y.G. Shen (pp. 2769-2774).

▶ The starting oxidation temperature of nanocomposite Ti–C_x–N_y thin films was 300°C irrespective of the carbon content; however their oxidation rate strongly depended on their carbon content. Higher carbon content caused more serious oxidation. ▶ After oxidation, the film hardness value remained up to the starting oxidation temperature, followed by fast decrease with increasing heating temperature. ▶ The residual compressive stress did not show a similar trend with the hardness. Its value was first increased with increase of heating temperature, and got its maximum at the starting oxidation temperature. ▶ The film surface roughness value was slightly increased with heating temperature till the starting oxidation temperature, a great decrease in surface roughness was followed with further increase of heating temperature.Two nanocomposite Ti–C_x–N_y thin films, TiC_0.95N_0.60 and TiC_2.35N_0.68, as well as one pure TiN, were deposited at 500°C on Si(100) substrate by reactive unbalanced dc-magnetron sputtering. Oxidation experiments of these films were carried out in air at fixed temperatures in a regime of 250–600°C with an interval of 50°C. As-deposited and oxidized films were characterized and analyzed using X-ray diffraction (XRD), microindentation, Newton's ring methods and atomic force microscopy (AFM). It was found that the starting oxidation temperature of nanocomposite Ti–C_x–N_y thin films was 300°C irrespective of the carbon content; however their oxidation rate strongly depended on their carbon content. Higher carbon content caused more serious oxidation. After oxidation, the film hardness value remained up to the starting oxidation temperature, followed by fast decrease with increasing heating temperature. The residual compressive stress did not show a similar trend with the hardness. Its value was first increased with increase of heating temperature, and got its maximum at the starting oxidation temperature. A decrease in residual stress was followed when heating temperature was further increased. The film surface roughness value was slightly increased with heating temperature till the starting oxidation temperature, a great decrease in surface roughness was followed with further increase of heating temperature.

Keywords: Nanocomposite; Oxidation rate; Starting heating temperature; Mechanical behaviors; Ti–C; _x; –N; _y; thin films

Effects of phase explosion in pulsed laser deposition of nickel thin film and sub-micron droplets by W.O. Siew; S.S. Yapl; T.K. Yong; C.H. Nee; T.Y. Tou (pp. 2775-2778).

Nickel (Ni) thin films were deposited on glass substrates in high vacuum and at room temperature with third-harmonic or 355-nm output from a nanosecond Nd:YAG laser. At low laser fluence of 1J/cm², the deposition rate was about 0.0016nm/shot which increased linearly until 4J/cm². Above 4J/cm², the onset of phase explosion in the ablation abruptly increased the optical emission intensity from laser-produced Ni plume as well as thin-film deposition rate by about 6×. The phase explosion also shifted the size distribution and number density of Ni droplets on its thin-film surface. On the other hand, the surface structures of the ablated Ni targets were compared between the scan-mode and the fixed-mode ablations, which may suggest that droplets observed on the thin-film surface were caused by direct laser-induced splashing of molten Ni rather than vapour-to-cluster condensation during the plume propagation.

Keywords: Pulsed laser deposition; Phase explosion; Droplets; Melt ejection

Influence of physicochemical–electronic properties of transition metal ion doped polycrystalline titania on the photocatalytic degradation of Indigo Carmine and 4-nitrophenol under UV/solar light by L. Gomathi Devi; S. Girish Kumar (pp. 2779-2790).

To understand the role of dopant inside TiO₂ matrix, anatase TiO₂ was doped with transition metal ions like Mn²⁺, Fe³⁺, Ru³⁺ and Os³⁺ having unique half filled electronic configuration and their photocatalytic activity was probed in the degradation of Indigo Carmine (IC) and 4-nitrophenol (NP) under UV/solar light. For comparison, TiO₂ was also doped with V⁵⁺, Ni²⁺ and Zn²⁺ metal ions having d⁰, d⁸ and d¹⁰ electronic configuration respectively. Irrespective of excitation source UV/solar light and nature of the organic pollutant, photocatalytic activities of doped photocatalysts followed the order: Mn²⁺-TiO₂>Fe³⁺-TiO₂>Ru³⁺-TiO₂≥Os³⁺-TiO₂>Zn²⁺-TiO₂>V⁵⁺-TiO₂>Ni²⁺-TiO₂ at an optimum concentration of dopant. Based on the experimental results obtained, it is proposed that the existence of dopant with half filled electronic configuration in TiO₂ matrix which is known to enhance the photocatalytic activity is not universal! Rather it is a complex function of several physicochemical–electronic properties of doped titania. Enhanced photocatalytic activity of Mn²⁺ (0.06at.%)-TiO₂ was attributed to the combined factors of high positive reduction potential of Mn²⁺/Mn³⁺ pairs, synergistic effects in the mixed polymorphs of anatase and rutile, smaller crystallite size with high intimate contact between two phases and favorable surface structure of the photocatalyst. Despite the intense research devoted to transition metal ion doped TiO₂, it is rather difficult to make unifying conclusion which is highlighted in this study.

Keywords: Transition metal ion doped titania; Electronic configuration of dopant; Physicochemical–electronic properties of doped titania; Synergistic effect; Vectorial interparticle electron transfer

Single crystals of mesoporous tungstenosilicate W-MCM-48 molecular sieves for the conversion of methylcyclopentane (MCP) by Ioana Fechete; Bertrand Donnio; Ovidiu Ersen; Thierry Dintzer; Amel Djeddi; François Garin (pp. 2791-2800).

Highly ordered W-MCM-48 mesoporous materials containing isolated W atoms in tetrahedral framework positions were successfully synthesized following the S⁺I⁻ pathway, up to a Si/W of 40. When tungsten content was increased up to a Si/W of 20, the ordered cubic structure was only partially maintained, and for a Si/W of 10 an amorphous phase was obtained. Highly isolated tetrahedral framework tungsten atoms in the W-MCM-48 with a Si/W of 40, have been identified by UV–vis band at 225nm, IR-TF band at 970cm⁻¹ and XRD. The W 4f XPS results suggest that the tungsten atoms exist in two oxidation states, W⁴⁺ and W⁵⁺. The morphology of the samples varies as a function of tungsten content. The W-MCM-48 samples with a Si/W ratio of 40 existed as crystals with a unique crystalline morphology consisting of cubes truncated rhombic dodecahedrons belonging to the cubic Ia3d space group, while the samples with a Si/W ratio of 20 exhibited a different morphology consisting of spheres and cubes truncated by rhombic dodecahedrons. A comparison of samples with Si/W of ∞, Si/W of 40 and Si/W of 20 was performed using the conversion of MCP carried out at 450°C under H₂.

Keywords: W-MCM-48; Self-assembly; Single crystals; Ring opening; Methylcyclopentane

Influence of the substrate position angle on the adhesion of ZnO thin films deposited on polyimide foil substrates by Hu Changji; Zhu Daoyun; He Zhenhui; Fu Weichun; Zhong Qi (pp. 2801-2805).

▶ The substrate position angle influences the ion flux in CVAD. ▶ The ion flux obviously influences the adhesion of ZnO films on polyimide substrates. ▶ The substrate position angle influences the microstructure of ZnO films deposited by CVAD.ZnO thin films, as polymer protection layers against ultraviolet radiation, were deposited on polyimide foil substrates using cathodic vacuum arc deposition technique. X-ray diffraction results showed that all the samples had (002) preferred orientation and the FWHM decreased as the position angle decreased. A fragmentation test was employed to investigate the influence of substrate position angle on the adhesion of ZnO thin films. It was found that the intrinsic adhesion between the ZnO film and the polyimide substrate is about 60MPa at the substrate position angle of 0°. When the position angle increases to ±60°, the value of intrinsic adhesion decreases to about 30MPa.

Keywords: PACS; 52.77.; Dq; 61.05.; cpZnO thin film; Cathodic vacuum arc deposition; Adhesion; Fragmentation test

A corrosion resistant cerium oxide based coating on aluminum alloy 2024 prepared by brush plating by Junlei Tang; Zhongzhi Han; Yu Zuo; Yuming Tang (pp. 2806-2812).

▶ The deposition of rare earth conversion coatings on aluminum alloys and other metals is considered as an effective method to replace chromate conversion coatings which have been prohibited in many fields for their toxicity. ▶ However, most of the reported methods to prepare cerium oxide based coatings were based on electrodeposition or chemical conversion processes. ▶ The addition of hydrogen peroxide results in cerium precipitates and solution instability. ▶ Deposition solutions with H₂O₂ are also difficult to recycle. ▶ In this study, a cerium oxide-based coating was deposited on aluminum alloy 2024 by brush. ▶ The brush plated cerium oxide based coatings on aluminum alloy showed good corrosion resistance. ▶ H₂O₂ is not necessary in the brush plating solution. ▶ The influence of the plating parameters on structure and corrosion resistance of the cerium oxide based coatings was studied.Cerium oxide based coatings were prepared on AA2024 Al alloy by brush plating. The characteristic of this technology is that hydrogen peroxide, which usually causes the plating solution to be unstable, is not necessary in the plating electrolyte. The coating showed laminated structures and good adhesive strength with the substrate. X-ray diffraction and X-ray photoelectron spectroscopy analysis showed that the coatings were composed of Ce(III) and Ce(IV) oxides. The brush plated coatings on Al alloys improved corrosion resistance. The influence of plating parameters on structure and corrosion resistance of the cerium oxide based coating was studied.

Keywords: Cerium oxide based coating; Aluminum alloy; Brush plating; Corrosion resistance

Electroless plating of silver on cenosphere particles and the investigation of its corrosion behavior in composite silicon rubber by Yong-jun Hu; Hai-yan Zhang; Xiao-ling Cheng; Feng Li; Tian-li Chen (pp. 2813-2817).

In this paper, silver coating on the surface of cenosphere particles was prepared by electroless plating method. The adhesion, oxidation resistance and corrosion resistance properties of silver coating mixed in silicone rubber were investigated. The corrosion characteristic of silver coating was evaluated by anodic polarization curves of the silicone rubber composite in sulfuric acid solution. The results showed that the silver coating on the surface of cenosphere particles was smooth and uniform. The silver film was not oxidized and peeling off during preparation of composite silicone rubber. The adhesion between the cenosphere particle and silver film was good enough. The anodic polarization curves of the silicone rubber composite showed typical activation and passivation transformation. The values of corrosion potential, the initiating passive potential and maintaining passivity potential of composites filled with different contents of Ag-coated cenosphere particles were the same and related to the nature of silver coating. The passive current density of composite increased with increase of the amount of Ag-coated cenosphere particles and was inversely proportional to the resistance of silicone rubber composite. The better the conductivity of silicone rubber composite is, the higher corrosion rate will be.

Keywords: PACS; 72.80.Tm; 81.65.−b; 82.45.BbElectroless plating; Silver coating; Oxidation resistance; Corrosion resistance; Composite silicon rubber

Role of Ge interlayer in the growth of high-quality strain relaxed SiGe layer with low dislocation density by Chengzhao Chen; Linghong Liao; Cheng Li; Hongkai Lai; Songyan Chen (pp. 2818-2821).

▶ High-quality strain relaxed SiGe layer has been fabricated on Si using a thin Ge interlayer grown at 330°C. ▶ The properties of SiGe layers with and without the low-temperature Ge interlayer are compared. ▶ The results indicate that the Ge interlayer plays an important role in the preparation of SiGe layer. ▶ The strain relaxed low-temperature Ge interlayer with coalesced island surface, acting as a stable and compliant template, could remove the cross-hatch misfit dislocation lines on surface and promote the strain relaxation in the SiGe layer homogeneously.High-quality strain relaxed SiGe layer has been fabricated on Si using a thin Ge interlayer grown at 330°C. The properties of SiGe layers with and without the low-temperature Ge interlayer are compared. The results indicate that the Ge interlayer plays an important role in the preparation of SiGe layer. The strain relaxed low-temperature Ge interlayer with coalesced island surface, acting as a stable and compliant template, could remove the cross-hatch misfit dislocation lines on surface and promote the strain relaxation in the SiGe layer homogeneously.

Keywords: SiGe layer; LT Ge; Strain relaxationPACS; 81.15; Gh; 68.55; ag; 78.66; Db

1.54μm emission mechanism of Er-doped zinc oxide thin films by Y.R. Jang; K.H. Yoo; J.S. Ahn; C. Kim; S.M. Park (pp. 2822-2824).

Zinc oxide (ZnO) and Er-doped zinc oxide (ZnO:Er) thin films were formed by pulsed laser deposition, and characterized by photoluminescence (PL) and X-ray diffraction (XRD) in order to clarify the 1.54μm emission mechanism in the ZnO:Er films. Er ions were excited indirectly by the 325nm line of a He–Cd laser, and the comparison of the ultraviolet to infrared PL data of ZnO and ZnO:Er films showed that the 1.54μm emission of Er³⁺ in ZnO:Er film appears at the expense of the band edge emission and the defect emission of ZnO. The crystallinity of the films was varied with the substrate temperature and post-annealing, and it was found that the intensity of the 1.54μm emission is strongly related with the crystallinity of the films. There are three processes leading to the 1.54μm emission; absorption of excitation energy by the ZnO host, energy transfer from ZnO to Er ions, and radiative relaxation inside Er ions, and it is suggested that the crystallinity plays an important role in the first two processes.

Keywords: PACS; 71.55.Gs; 78.55.EtZnO; Er doping; Photoluminescence; 1.54; μm emission

Droplet printing through bubble contact in the laser forward transfer of liquids by M. Duocastella; J.M. Fernández-Pradas; J.L. Morenza; P. Serra (pp. 2825-2829).

Display Omitted▶ A bubble contact deposition mechanism for the LIFT of liquids has been unveiled. ▶ This mechanism consists in the contact of the generated cavitation bubble with the receptor substrate. ▶ To attain the highest resolution of LIFT, the bubble contact should be avoided. ▶ This can be achieved at low fluences and/or large donor–receptor separations.The deposition process of the laser-induced forward transfer of liquids at high laser fluences is analyzed through time-resolved imaging. It has been found that, at these conditions, sessile droplets are deposited due to the contact of a generated cavitation bubble with the receptor substrate, in contrast to the jet contact mechanism observed at low and moderate laser fluences. The bubble contact results in droplets with a larger diameter, a smaller contact angle and a lower uniformity than those of the jet mechanism. Therefore, in order to attain a high degree of resolution this mechanism should be prevented.

Keywords: Laser direct-writing; Time-resolved imaging; Laser printing; Micropatterning

Evaluation of Nanostructured coating layers formed on Ni balls during mechanical alloying of Cu powder by Iman Farahbakhsh; Alireza Zakeri; Palavesamuthu Manikandan; Kazuyuki Hokamoto (pp. 2830-2837).

▶ A novel coating method was used to deposit a nickel–copper solid solution on the surface of nickel balls in a planetary ball mill. ▶ Diffusion is caused by the impact of nickel balls in addition to the formation of Ni–Cu solid solution as a surface coating layer. ▶ XRD results revealed the presence of a solid solution and nanocrystalline structure on the surface.A novel coating method utilizing mechanical alloying was used to deposit a nickel–copper solid solution on the surface of nickel balls in a planetary ball mill. Mechanically milled copper powders were deposited by cold welding on the activated surface of the nickel balls. The impact of the nickel balls causes surface wear, leading to formation of mixed layered particles of copper–nickel and rewelding. In addition, diffusion takes place through the coating layer to form a Ni–Cu solid solution. The hardness of the coating reached a threefold increase (HV_0.01594) in comparison with the substrate hardness. Microstructural characterization of the coating surface performed using an optical microscope, SEM, and EPMA indicates that, with appropriate processing conditions, a thick, fully dense coating can be metallurgically bonded to the nickel balls. XRD results revealed the presence of a solid solution and nanocrystalline structure.

Keywords: Surface coatings; Mechanical alloying; Microstructure; Ni–Cu solid solution; EPMA; Mechanical diffusion

Study of molybdenum/lanthanum-based composite conversion coatings on AZ31 magnesium alloy by Lihui Yang; Junqing Li; Cunguo Lin; Milin Zhang; Jianhua Wu (pp. 2838-2842).

The molybdenum/lanthanum-based (Mo/La) composite conversion coating on AZ31 magnesium alloy was investigated and the corrosion resistance was evaluated as well. The morphology, composition and corrosion resistance of the coating were studied by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and potentiodynamic polarization analysis, respectively. The results revealed that the conversion coating consisted of spherical nodular particles, which was mainly composed of Mo, La, O and Mg. After conversion treatment the corrosion potential shifts about 500mV positively, and the corrosion current density decreases two orders of magnitude. The corrosion resistance of AZ31 alloy is remarkably improved by Mo/La composite conversion coating.

Keywords: Magnesium alloy; Molybdenum; Lanthanum; Conversion coating; Corrosion resistance

Microstructures and properties of electrical discharge strengthened layers on 65Mn steel by Dong Chunjie; Zhang Jianhua; Xu Jiayuan; Song Xichao; Zhao Yunfeng (pp. 2843-2849).

Here, we reported the successful surface modification with silicon electrode via electrical discharging. During the modification procedure, metallurgy reaction occurred between silicon electrode and workpiece materials, in which kerosene was discomposed and a strengthened layer was obtained on the surface of workpiece materials. The influence of processing parameters on the modified layer was also investigated. Our experimental results elucidated that an amorphous nano-crystalline alloy layer can be fabricated on the surface of 65Mn steel (ASTM:1566) in a controllable way. By forming a strengthened nano-layer, the hardness of 65Mn steel as well as the wear and corrosion resistance was obviously enhanced. In addition, a homogenous strengthened nano-layer can be formed by utilizing ultrasonic vibration of silicon electrode.

Keywords: Electrical discharge; Surface modification; Microstructure and performance; Ultrasonic vibration

Modification of interface structure and contact resistance between a carbon nanotube and a gold electrode by local melting by Koji Asaka; Motoyuki Karita; Yahachi Saito (pp. 2850-2853).

▶ The structural dynamics of the end-contact process of carbon nanotubes are observed. ▶ The contact structure between a carbon nanotube and gold is modified by local melting. ▶ The modification of the contact structure reduces the contact resistance.The electrical connection between a multiwalled carbon nanotube (MWNT) and a gold electrode on applying an electric current was studied by performing in situ transmission electron microscopy observations while simultaneous measuring the bias voltage and the electric current. The tip of the MWNT was brought into contact with the gold surface. When a current density of ∼10⁸A/cm² flowed through the contact, the gold surface started to melt along the surface of the MWNT tip due to Joule heating. At about twice the current density, a drastic change was observed in the structure of the gold surface in the contact region. This structural change increased the contact area between the MWNT tip and gold, which reduced the electrical contact resistance.

Keywords: Carbon nanotube; Contact resistance; Connection process; Local melting; In situ; transmission electron microscopy

Ablation yield and angular distribution of ablated particles from laser-irradiated metals: The most fundamental determining factor by Dilawar Ali; M.Z. Butt; M. Khaleeq-ur-Rahman (pp. 2854-2860).

▶ The angular distribution of LPP ions from target metals has no systematic correlation with the square-root of atomic mass of the target metals. ▶ The angular distribution of LPP ions exhibits systematic dependence on the room temperature Debye–Waller's thermal parameter B or the mean-square amplitude of atomic vibrations 〈 u²〉. ▶ The ablation yield (atoms/shot) of target metals under identical irradiation conditions is also a function of the room temperature B-factor or 〈 u²〉.Five metals (Zn, Cu, Ni, Ti, and Mo) were irradiated with 150 shots of a Q-switched Nd:YAG pulsed laser in a vacuum of 10⁻³torr. The ions projected out of the laser-produced plasma (LPP) plume were detected by CR-39 detectors positioned at −15°, 0°, 30°, 60°, and 90° with respect to the target-surface normal at a distance of 5cm from the target in each case. The angular distribution of LPP ions, which is characterized by the exponent n of cosⁿ θ distribution, is given by n=2.5–11 for the five target metals. The value of the exponent n has no systematic correlation with the square-root of atomic mass of the target metals but exhibits systematic dependence on the room temperature Debye–Waller's thermal parameter B or the mean-square amplitude of atomic vibrations 〈 u²〉. Likewise, the ablation yield (atoms/shot) of the twelve target metals investigated by Thestrup et al. (2002) under identical irradiation conditions is a function of the room temperature B-factor or 〈 u²〉.

Keywords: Nd:YAG laser; Ablation yield; Angular distribution; Sublimation energy; Debye–Waller's thermal parameter

Structural dependence of the efficiency of functionalization of silica-coated FeO_x magnetic nanoparticles studied by ATR-IR by Angelo Vargas; Ivan Shnitko; Alexandra Teleki; Stephen Weyeneth; Sotiris E. Pratsinis; Alfons Baiker (pp. 2861-2869).

▶ Propylamino functionalization of magnetic silica-coated FeO_x nanoparticles prepared by different methods, including coprecipitation and flame aerosol synthesis, shows different efficiency. ▶ ATR-IR spectroscopy combined with a specific surface reaction allows to determine specifically the chemically available aminopropyl groups on the surface. ▶ Elemental analysis gives an upper bound for the concentration of aminopropyl groups, while ATR-IR additionally provides information about the chemical availability of these groups. ▶ Depending on the structure and surface properties of the silica-coated FeO_x nanoparticles results from elemental analysis and ATR-IR measurements can deviate significantly.The efficiency of propylamino functionalization of magnetic silica-coated FeO_x nanoparticles prepared by different methods, including coprecipitation and flame aerosol synthesis, has been evaluated by attenuated total reflection infrared spectroscopy (ATR-IR) combined with a specific surface reaction, thus revealing the availability of the grafted functional groups. Large differences in the population of reactive groups were observed for the investigated materials, underlining the tight relation between the structure of nanoparticles and their suitability for organic functionalization. The materials possessed different core structure, surface area, and porosity, as evidenced by transmission electron microscopy and nitrogen adsorption–desorption isotherms. Grafting of aminopropyl groups using a standard procedure based on reaction with (3-aminopropyl)trimethoxysilane as source of the propylamino groups was performed, followed by classical dry analysis methods to determine the specific concentration of the organic functional groups (in mmolg⁻¹ of material). ATR-IR spectroscopy in a specially constructed reactor cell was applied as wet methodology to determine the chemically available amount of such functional groups, showing that the materials possess largely different loading capacity, with a variability of up to 70% in the chemical availability of the organic functional group. The amount of (3-aminopropyl)trimethoxysilane used for functionalization was optimized, thus reaching a saturation limit characteristic of the material.

Keywords: Magnetic nanoparticles; Magnetic separation; Population of functional groups; ATR-IR spectroscopy; Iron oxide; Silica; Flame-synthesis; Aminopropyl; Benzaldehyde

Protons’ generation by laser irradiation at 5×10⁹W/cm² from silicon dielectric targets containing an excess of hydrogen by F. Caridi; A. Picciotto; L. Torrisi; L. Giuffrida; P. Bellutti (pp. 2870-2874).

A study of silicon plasma generated in vacuum by 532nm Nd:YAG laser at intensities of about 5×10⁹W/cm² from dielectric targets containing a relatively huge quantity of hydrogen was presented.Time-of-flight technique was employed to measure the particles’ energy and the relative yield with respect to other ion species. Plasma-accelerated ions show Coulomb–Boltzmann-shifted distributions depending on their charge state.Mass quadrupole spectrometry allowed the estimation of the relative hydrogen amount inside the different samples considered: silicon (Si), silicon nitride (Si₃N₄) and hydrogenated annealed silicon (Si(H)) as a function of the ablation depth and irradiation time.Depth profiles of the laser craters permit to calculate the ablation yield at the used laser fluence. The plasma temperature and density was evaluated by the experimental data. A special regard is given to the protons’ generation process occurring inside the plasma, due to the possible influence of the hydrogen excess on the treated samples in comparison to the not-hydrogenated silicon ones.

Keywords: Proton beams; Laser-plasma; Time-of-flight technique

Acid–base properties of Ni–MgO–Al₂O₃ materials by Wojciech Gac (pp. 2875-2880).

▶ Acid–base-properties of Ni–MgO–Al₂O₃ systems were related to the Ni/Mg ratio. ▶ The increase of Ni/Mg ratio decreased stability of the hydrotalcite structure. ▶ Thermal treatment of the samples in hydrogen led to the structural and surface changes.Ni–MgO–Al₂O₃ materials of different Ni/Mg ratios were prepared by the co-precipitation method. Acid–base properties of the samples after calcination and reduction were examined by the temperature programmed desorption of ammonia and carbon dioxide. Thermal treatment of the materials in air at 400°C led to the formation of hydrotalcite-like phases. The increase of Ni/Mg ratio decreased the stability of the hydrotalcite structure. The number and the strength of acid and base sites were related to the Ni/Mg ratio and thermal treatment conditions of materials. It was found that the replacement of Ni with Mg decreased the acidity and increased basicity of the surface of oxide materials. Thermal treatment of the samples in hydrogen led to the structural changes. The presence of magnesia improved thermal stability. The ratio of the number of acid to base sites in the reduced samples gradually increased with the increase of magnesia content.

Keywords: Ni–MgO–Al; ₂; O; ₃; Hydrotalcite; TPD; Acidity; Basicity

Fabrication and lithium electrochemistry of InSe thin film by Wen-Jing Li; Yong-Ning Zhou; Zheng-Wen Fu (pp. 2881-2885).

▶ InSe thin film has been successfully fabricated by pulsed-laser deposition method. ▶ The reversible capacity of InSe electrode of 410mAh/g with the volumetric capacity of about 3302mAh/cm³ was achieved. ▶ Both alloying/de-alloying processes and selenidation/reduction processes were revealed. ▶ InSe was found to be a novel candidate of anode materials for rechargeable lithium batteries.InSe thin film has been successfully fabricated by pulsed-laser deposition method. Electrochemical behavior of Li/InSe cell has been investigated by Galvanostatic cycling and cyclic voltammetry measurements for the first time. The reversible capacity of InSe electrode of 410mAh/g with the volumetric capacity of about 3302mAh/cm³ was achieved at a current density of 0.05mA/cm². By using XRD and XPS measurements, both alloying/de-alloying processes and selenidation/reduction processes were revealed during the electrochemical cycling of InSe thin film electrode. InSe was found to be a novel candidate of anode materials for rechargeable lithium batteries.

Keywords: InSe; Anode materials; Lithium ion batteries; Pulsed laser deposition

Physical mechanism of silicon ablation with long nanosecond laser pulses at 1064nm through time-resolved observation by Yun Zhou; Benxin Wu; Sha Tao; Andrew Forsman; Yibo Gao (pp. 2886-2890).

▶ Long nanosecond pulsed laser ablation of silicon at 1064nm has been studied. ▶ Material removal occurs through vaporization followed by liquid ejection. ▶ Ejected liquid front changes linearly with time. ▶ Liquid ejection is unlikely due to phase explosion.Nanosecond (ns) laser ablation can provide a competitive solution for silicon micromachining in many applications. However, most of the previous studies focus on ns lasers at visible or ultraviolet (UV) wavelengths. The research is very limited for ns lasers at infrared (e.g., 1064nm) wavelengths (which often have the advantage of much lower cost per unit average output power), and the research is even less if the ns laser also has a long pulse duration on the order of ∼100ns. In this paper, time-resolved observation using an ICCD (intensified charge-coupled device) camera has been performed to understand the physical mechanism of silicon ablation by 200-ns and 1064-nm laser pulses. This kind of work has been rarely reported in the literature. The research shows that for the studied conditions, material removal in laser silicon ablation is realized through surface vaporization followed by liquid ejection that occurs at a delay time of around 200–300ns. The propagation speed is on the order of ∼1000m/s for laser-induced plasma (ionized vapor) front, while it is on the order of ∼100m/s or smaller for the front of ejected liquid. It has also been found that the liquid ejection is very unlikely due to phase explosion, and its exact underlying physical mechanism requires further investigations.

Keywords: Nanosecond laser ablation; Laser silicon ablation

Surface modification of argon/oxygen plasma treated vulcanized ethylene propylene diene polymethylene surfaces for improved adhesion with natural rubber by Ganesh C. Basak; Abhijit Bandyopadhyay; Sudarsan Neogi; Anil K. Bhowmick (pp. 2891-2904).

▶ Plasma treatment changes surface characteristics of vulcanized EPDM rubber. ▶ The degree of modification depends on composition of plasma and process parameters. ▶ Peel strength is greatly improved due to increase in polarity and micro-roughness.Vulcanized ethylene propylene diene polymethylene (EPDM) rubber surface was treated in a radio frequency capacitatively coupled low pressure argon/oxygen plasma to improve adhesion with compounded natural rubber (NR) during co-vulcanization. The plasma modified surfaces were analyzed by means of contact angle measurement, surface energy, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray sulfur mapping and atomic force microscopy. Several experimental variables such as plasma power, length of exposure time and composition of the argon–oxygen gas mixture were considered. It was delineated that plasma treatment changed both surface composition and roughness, and consequently increased peel strength. The change in surface composition was mainly ascribed to the formation of C–O and –CO functional groups on the vulcanized surfaces. A maximum of 98% improvement in peel strength was observed after plasma treatment.

Keywords: Plasma; Rubber; Co-curing process; Peel

Effects of the ultrasonic flexural vibration on the interaction between the abrasive particles; pad and sapphire substrate during chemical mechanical polishing (CMP) by Wenhu Xu; Xinchun Lu; Guoshun Pan; Yuanzhong Lei; Jianbin Luo (pp. 2905-2911).

▶ The actions of the ultrasonic and silica abrasive particles were the main factors in the sapphire material removal rate (MMR). ▶ The chemical additives were helpful to decrease the roughness of sapphire. ▶ The effects of the flexural vibration on the interaction between the silica abrasive particles, pad and sapphire substrate improved the sapphire's MRR.In this paper, the technique of ultrasonic flexural vibration assisted chemical mechanical polishing (UFV-CMP) was used for sapphire substrate CMP. The functions of the polishing pad, the silica abrasive particles, and the chemical additives of the slurry such as pH value regulator and dispersant during the sapphire's UFV-CMP were investigated. The results showed that the actions of the ultrasonic and silica abrasive particles were the main factors in the sapphire material removal rate (MMR) and the chemical additives were helpful to decrease the roughness of sapphire. Then the effects of the flexural vibration on the interaction between the silica abrasive particles, pad and sapphire substrate from the kinematics and dynamics were investigated to explain why the MRR of UFV-CMP was bigger than that of the traditional CMP. It indicated that such functions improved the sapphire's MRR: the increasing of the contact silica particles’ motion path lengths on the sapphire's surface, the enhancement of the contact force between the contact silica particles and the sapphire's surface, and the impaction of the suspending silica particles to the sapphire's surface.

Keywords: Ultrasonic flexural vibration; Chemical mechanical polishing (CMP); Sapphire substrate; Silica abrasive particles; Interaction

Surface studies of novel hydrophobic active carbons by Robert H. Bradley; Martin W. Smith; Aurik Andreu; Maurizio Falco (pp. 2912-2919).

▶ We have synthesized a microporous carbon with a hydrophobic surface which gives enhanced breakthrough times (+40%) for filter-beds used for the separation of certain organic vapours under high humidity (80% RH) conditions. ▶ These materials also show improved (reduced) ageing under high humidity storage compared to standard carbons. ▶ They also give us an insight into the fundamental mechanism of water adsorption by active carbons and, by disrupting this process, allowing us to test current theories and ideas.The efficient adsorption of toxic organic species from humid airstreams by active carbons is impeded by the competitive adsorption of water vapour which, at low values of p/ p^s, occurs at specific (polar) adsorption sites located at the edges of the carbon layer-planes and at in-plane defects. At higher pressures, adsorption in micropores and mesopores also occurs. The concentration of polar adsorption sites therefore determines the hydrophilicity of the carbon structure and their accelerated formation, by exposure to air and water vapour, is also responsible for the ‘ageing’ of active carbons. Overall, the adsorption of water reduces the volume of porosity available for the adsorption of target species and the hydrophilic nature of active carbons is recognized as a major barrier to their effective use in many applications.We present here results for the adsorption of nitrogen, organic and water vapours by a hydrophobic respirator granular active carbon produced by the thermal treatment of a base carbon, to desorb polar oxygen groups, followed by use of a plasma enhanced chemical vapour deposition (PECVD) treatment to apply a hydrophobic, fluorine containing, surface nanolayer. We show that at equivalent %RH values the treated carbon adsorbs significantly less water compared to an untreated (control) carbon and that the treatment does not reduce the levels of open porosity or impede the adsorption of a range of organic vapours at ambient temperatures. Preliminary evidence for the presence, after treatment, of constrictions at pore entrances which act as molecular gates is also presented. The treated carbon (after ageing for 6 weeks at 80%RH) is shown to have greater adsorptivity than an untreated base carbon toward hexane present in a humid (80%RH) airstream. This results in a 39% increase in break-through time. These hydrophobic properties persist one year after manufacture. The mechanism leading to the modified water adsorption properties is the partial desorption of polar oxygen sites followed by deposition at the external carbon surfaces of hydrophobic plasma polymer species. This reduces the polar surface free energy of the carbon and hence the amount of water adsorption occurring by the primary mechanism. This in turn retards the diffusion of water molecules into the micropores and leads to lower adsorption volumes at higher pressures.

Keywords: Active carbon; Hydrophobic; Plasma enhanced CVD; XPS; Water adsorption

Ultrathin amorphous Ni–Ti film as diffusion barrier for Cu interconnection by B.T. Liu; L. Yang; X.H. Li; K.M. Wang; Z. Guo; J.H. Chen; M. Li; D.Y. Zhao; Q.X. Zhao; X.Y. Zhang (pp. 2920-2922).

▶ 5-nm-thick amorphous Ni–Ti film in Cu/Ni–Ti/Si heterostructure is investigated as the barrier layer between Cu and Si. ▶ No Cu silicides are found for the samples annealed up to 750°C. ▶ Failure of the Ni–Ti barrier is attributed to dewetting and agglomeration of the Cu. ▶ An ultrathin amorphous Ni–Ti film can be a good barrier material candidate as Cu metalization at temperatures below 700°C.5-nm-thick amorphous Ni–Ti films deposited on Si by magnetron sputtering, annealed at various temperatures in high vacuum, have been studied as diffusion barriers for Cu interconnection using X-ray diffraction, atomic force microscopy and four-probe methods. Although no Cu silicide peaks are found from X-ray diffraction patterns of the samples annealed up to 750°C, it is found that the sheet resistance of Cu/Ni–Ti/Si decreases with the increase of annealing temperature and then slightly increases when the annealing temperature is higher than 700°C. Root mean square roughness of Cu/Ni–Ti/Si increases with the increase of annealing temperature and many island-like grains present on the surface of the 750°C annealed sample, which is ascribed to dewetting and agglomeration.

Keywords: Cu interconnect; Ni–Ti; Diffusion barrier; Dewetting; Agglomeration

High catalytic performance of Pt nanoparticles on plasma treated carbon nanotubes for electrooxidation of ethanol in a basic solution by Zhongqing Jiang; Zhong-jie Jiang; Yuedong Meng (pp. 2923-2928).

Nanosized platinum particles deposited on plasma treated multi-walled carbon nanotubes have been used in electrocatalytic oxidation of ethanol in a basic solution and exhibit significant higher catalytic activities, higher Pt utilization efficiency (93.77%) and improved durability in comparison to the commercial available JM Pt/C catalyst.Nanosized Pt particles deposited on plasma treated multi-walled carbon nanotubes have been used in electrocatalytic oxidation of ethanol in a basic solution. These Pt nanoparticles have very narrow size distribution and exhibit significant higher catalytic activities, higher Pt utilization efficiency (93.77%) and improved durability in comparison to the commercial available Johnson Matthey Pt/C catalyst.

Keywords: Multi-walled carbon nanotubes; Plasma surface modification; Electrocatalysts; Direct ethanol fuel cells; Pt utilization efficiency

Effect of cationic/anionic organic surfactants on evaporation induced self assembled tin oxide nanostructured films by Kamalpreet Khun Khun; Aman Mahajan; R.K. Bedi (pp. 2929-2934).

▶ Preparation of cationic/anionic organic surfactant assisted tin oxide thin films. ▶ These films are systematically characterized for structural, electrical and optical properties. ▶ We are successful in producing highly porous and nanostructured tin oxide films which will be suitable for optoelectronic and gas sensing applications.Tin oxide nanostructures with well defined morphologies have been obtained through an evaporation induced self assembly process. The technique has been employed using an ultrasonic nebulizer for production of aersol and its subsequent deposition onto a heated glass substrate. The precursor used for aersol production was modified by introducing cationic and anionic surfactants namely cetyl trimethyl ammonium bromide and sodium dodecyl sulphate respectively. The effect of surfactants on the structural, electrical and optical properties of self assembled tin oxide nanostructures were investigated by using X-ray diffraction, field emission scanning electroscope microscopy, two probe technique and photoluminiscence studies. The results reveal that high concentration of surfactants in the precursor solution leads to reduction in crystallite size with significant changes in the morphology of tin oxide nanostructures. Photoluminiscence studies of the nanostructures show emissions in the visible region which exhibit marked changes in the intensities upon variation of surfactants in the precursor solutions.

Keywords: Tin oxide; Thin films; Structure and morphology; Electrical properties; Optical properties

Fabrication of ZnO:Mn nanoparticles with organic shell in a highly alkaline aqueous environment by Santa Chawla; Sharda; K. Jayanthi (pp. 2935-2939).

▶ This research work highlights the effectiveness of an aqueous co precipitation method in a highly alkaline environment for doping of Mn into ZnO lattice as well as in situ capping of ZnO:Mn nanoparticles by MSA. ▶ MSA capping enhances the photoluminescence emission of ZnO:Mn nanoparticles. ▶ MSA capping renders the nanoparticles biofunctionalized for biological applications.Synthesis of undoped and Mn doped ZnO nanoparticles by an inclusive co precipitation method and in situ capping with heteromultifunctional organic stabilizer mercaptosuccinic acid (MSA) in a core shell structure, in highly alkaline aqueous matrix have been accomplished. Near room temperature synthesis resulted in high quality monophasic wurtzite hexagonal structure of rod shaped nanoparticles of bare ZnO:Mn with no signature of dopant as separate phase. MSA capping resulted in nanoball like formation. Thermo gravimetric analysis (TGA) and FTIR confirmed MSA capping. ZnO: Mn particles emit in orange and red when excited by UV and blue light. Surface modification makes the nanoparticles hydrophilic with active organic surface easy for bioconjugation with any ligand and can have applications in drug delivery or as nanoscale fluorescent probe in a biological system.

Keywords: Co precipitation technique; Mercaptosuccinic acid; Photoluminescence; Capping

Fabrication of multiwalled carbon nanotubes in the channels of iron loaded three dimensional mesoporous material by catalytic chemical vapour deposition technique by T. Somanathan; N. Gokulakrishnan; G. Chandrasekar; A. Pandurangan (pp. 2940-2943).

▶ MWNTs performed in the channels of iron loaded 3D mesoporous KIT-6 material through CCVD. ▶ Thick graphene layers about 10nm composed of 29 graphene sheets. ▶ High yield than other reported MWNTs synthesised using mesoporous materials. ▶ Excellent graphitisation than commercial MWNTs.The growth of multiwalled carbon nanotubes (MWNTs) was successfully achieved in the channels of three dimensional (3D) iron loaded mesoporous matrices (KIT-6) by employing catalytic chemical vapour deposition (CCVD) technique. The synthesised MWNTs, which were characterised by SEM, TEM and Raman spectroscopy, consist of thick graphene layers of about 10nm composed of 29 graphene sheets with inner and outer diameter of ∼17nm and ∼37nm, respectively. The Raman spectrum showed the formation of well-graphitised MWNTs with significantly higher I_G/ I_D ratio of 1.47 compared to commercial MWNTs. Comparatively, 2wt% Fe loaded KIT-6 material produced a better yield of 91%, which is also highest compared with the report of MWNTs synthesis using mesoporous materials reported so far.

Keywords: MWNTs; CCVD; Fe loaded KIT-6; Mesoporous materials

Electrodeposition and growth mechanism of SnSe thin films by Mustafa Biçer; İlkay Şişman (pp. 2944-2949).

▶ The electrodeposition of the SnSe thin films was studied using cyclic voltammetry, compositional, structural, optical measurements and surface morphology. ▶ The film growth proceeds via nucleation, growth of film layer and formation of needle-like particles on the overlayer of the film. ▶ The morphologies of SnSe thin films could be changed from spherical grains to platelet-like particles as the deposition potential increases.Tin selenide (SnSe) thin films were electrochemically deposited onto Au(111) substrates from an aqueous solution containing SnCl₂, Na₂SeO₃, and EDTA at room temperature (25°C). The electrochemical behaviors and the codeposition potentials of Sn and Se were explored by cyclic voltammetry. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and UV–vis absorption spectroscopy were employed to characterize the thin films. When the electrodeposition potential increased, the Se content in the films decreased. It was found that the stoichiometric SnSe thin films could be obtained at −0.50V. The as-deposited films were crystallized in the preferential orientation along the (111) plane. The morphologies of SnSe films could be changed from spherical grains to platelet-like particles as the deposition potential increases. The SEM investigations show that the film growth proceeds via nucleation, growth of film layer and formation of needle-like particles on the overlayer of the film. The optical absorption study showed the film has direct transition with band gap energy of 1.3eV.

Keywords: SnSe; Thin films; Electrodeposition; Surface morphology

Spectroscopic characterization of β-FeSi₂ single crystals and homoepitaxial β-FeSi₂ films by XPS and XAS by F. Esaka; H. Yamamoto; H. Udono; N. Matsubayashi; K. Yamaguchi; S. Shamoto; M. Magara; T. Kimura (pp. 2950-2954).

▶ XPS and XAS analyses reveal the chemical states of β-FeSi₂ single crystals and films. ▶ The thickness of surface oxide layers can be estimated by energy-tunable XPS. ▶ The annealing of β-FeSi₂ single crystal at 1173K induces the formation of FeSi. ▶ Homoepitaxial films can be grown on the β-FeSi₂ single crystal by MBE.Chemical state analysis by a combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is performed for β-FeSi₂ single crystals and homoepitaxial β-FeSi₂ films. The Si 2p XPS and Fe L-edge XAS spectra imply that the annealing at 1173K to remove native oxide layers on the crystal induces the formation of FeSi in the surface. The formation of FeSi is also confirmed by Si K-edge XAS analysis. For the homoepitaxial β-FeSi₂ films grown on the crystals, the Si K-edge XAS spectra indicate that structurally homogeneous β-FeSi₂ films can be grown on the β-FeSi₂ single crystals when the substrate temperatures of 973 and 1073K are applied for molecular beam epitaxy (MBE). Consequently, it is indicated that the combination of XPS and XAS using synchrotron radiation is a useful tool to clarify chemical states of β-FeSi₂ single crystals and homoepitaxial β-FeSi₂ films, which is important to reveal optimized growth conditions of homoepitaxial films.

Keywords: XPS; XAS; Fe L-edge; Si K-edge; Iron silicide; Depth profiling

Preparation and properties of ZnS superhydrophobic surface with hierarchical structure by Lujun Yao; Maojun Zheng; Shuanghu He; Li Ma; Mei Li; Wenzhong Shen (pp. 2955-2959).

▶ Preparation of hierarchical ZnS nanostructured film. ▶ Super water-repellent property was attributed to its special structure. ▶ Effective self-cleaning and dynamic water-repelling phenomenon were demonstrated.A novel ZnS hierarchical structure composed of nanorod arrays with branched nanosheets and nanowires grown on their upside walls, was synthesized over Au-coated silicon substrate via chemical vapor deposition technique. Contact angle and sliding angle of this hierarchical film with no surface modification were measured to be about 153.8° and 9.1° for 5μl water droplets. Self-cleaning behavior and dynamic water-repelling performance were clearly demonstrated. In addition, electrowetting transition phenomenon from superhydrophobic to hydrophilic state happened when a critical bias ∼7.0V was applied. Below this threshold voltage, the contact angle change is little. This work for the first time reports the creation of ZnS superhydrophobic surface and could enrich its research field as surface functional materials.

Keywords: Key words; Novel ZnS nanostructure; Chemical vapor deposition; Self-cleaning; Super water-repellent; Electrowetting

Control growth of catalyst-free high-quality ZnO nanowire arrays on transparent quartz glass substrate by chemical vapor deposition by X.H. Wang; R.B. Li; D.H. Fan (pp. 2960-2964).

▶ Morphology-controllable ZnO nanowire arrays on transparent quartz glass substrate have been successfully synthesized by a simple chemical vapor deposition technique. The results indicated that the evaporation temperature and the buffer layer play important roles on controlling the morphology. A proper growth temperature, 480°C and thicker buffer layer 40nm in this work result in the ZnO nanowire arrays of the best alignment and density. The room-temperature photoluminescence spectrum showed that the buffer layer has also great effects on optical properties of ZnO nanowire arrays. The integrated intensity ratio [ I_UV/ I_{Visible band}] of the ZnO UV emission peak to visible band emission decreases with the increasing thickness. The obtained nanowire arrays have transmittance of above 50% in the visible region.ZnO nanowire arrays have been successfully synthesized on transparent quartz glass substrate by chemical vapor deposition technique. Our work demonstrates the critical role of the growth temperature and the buffer layer on the effective control of the morphology of ZnO nanowires. A proper growth temperature and the thicker buffer layer could promise the good alignment and high density of the nanowires. The room-temperature photoluminescence spectrum shows that the buffer layer has also great effects on optical properties of ZnO nanowire arrays. The integrated intensity ratio [ I_UV/ I_{Visible band}] of the ZnO UV emission peak to visible band emission decreases with the increase of the thickness of the buffer layers. The obtained nanowire arrays have transmittance of above 50% in the visible region.

Keywords: Transparent quartz glass substrate; ZnO nanowire arrays; Chemical vapor deposition; Optical properties

Quantitative test method for evaluation of anti-fingerprint property of coated surfaces by Linda Y.L. Wu; S.K. Ngian; Z. Chen; D.T.T. Xuan (pp. 2965-2969).

Display Omitted▶ Artificial fingerprint liquid is formulated from PDMS, MP and artificial sweat. ▶ Direct determination of anti-fingerprint property of a coated surface can be made. ▶ Test method is confirmed by correlating to actual human fingerprints. ▶ Anti-fingerprint property can be achieved on smooth and optically clear surfaces.An artificial fingerprint liquid is formulated from artificial sweat, hydroxyl-terminated polydimethylsiloxane and a solvent for direct determination of anti-fingerprint property of a coated surface. A range of smooth and rough surfaces with different anti-fingerprint (AF) properties were fabricated by sol–gel technology, on which the AF liquid contact angles, artificial fingerprint and real human fingerprints (HF) were verified and correlated. It is proved that a surface with AF contact angle above 87° is fingerprint free. This provides an objective and quantitative test method to determine anti-fingerprint property of coated surfaces. It is also concluded that AF property can be achieved on smooth and optically clear surfaces. Deep porous structures are more favorable than bumpy structure for oleophobic and AF properties.

Keywords: Anti-fingerprint; Contact angle; Oleophobicity; Hydrophobicity; Coating

Effect of Sn particle size on the intermetallic compound formations of cold sprayed Sn–Ni coatings by K.H. Ko; H. Lee; J.O. Choi (pp. 2970-2977).

▶ Effects of small Sn particles on the morphology evolution and intermetallic compound formation of cold sprayed Sn–Ni system on Ni and Cu substrate were investigated. ▶ The different reactivity between Ni–Sn and Cu–Sn could have an influence on the formation of intermetallic compounds. It could be considered that the activation energy barrier of Cu–Sn system was lower that of Ni–Sn combination case. ▶ The reactivities of small particles were turned out to be inferior to corresponding large size of materials. It was suggested that heavier oxide scale of raw material is responsible to this. ▶ It was concluded that the particle size is very important with regard to the formation of intermetallic compounds in annealed cold sprayed coatings.Comparative studies on the intermetallic compound (IMC) formations of small (aggregated) and large Sn (irregular) with Ni and Cu in cold gas dynamic sprayed coatings were carried out. The Sn with high purity were selected and prepared as raw materials mixture in order to be sprayed onto Ni and Cu plate-shape substrates. The small particles of Sn (<1μm) were successfully coated under conventional coating parameters when they are mixed with larger powder materials. And microstructural observation regards to compound formation similarly worked out for both small and large Sn mixture. However, the intermetallic formation behavior was turned out to be different. After post-annealing, the larger Sn particles in the composite coating formed larger amount of IMC with Ni than small Sn although, owing to larger interfacial area, more intensive reactivities were expected. Also, there were significant differences in the size and distribution of eutectic pores as well.

Keywords: Sn; Ni; Cold spray; Intermetallics; Particle size; Annealing

Functional groups grafted nonwoven fabrics for blood filtration—The effects of functional groups and wettability on the adhesion of leukocyte and platelet by Chao Yang; Ye Cao; Kang Sun; Jiaxin Liu; Hong Wang (pp. 2978-2983).

▶ Surface functional groups and wettability had obvious impact on blood cell adhesion. ▶ The surface bearing SO3H had highest platelet adhesion. ▶ The surface bearing sulfobetaine had lowest platelet adhesion. ▶ The adhesion of leukocyte to the surface bearing OH only was highest and unchanged. ▶ The platelet and leukocyte adhesion reduced as the surface wettability increased.In this work, the effects of grafted functional groups and surface wettability on the adhesion of leukocyte and platelet were investigated by the method of blood filtration. The filter materials, poly(butylene terephthalate) nonwoven fabrics bearing different functional groups including hydroxyl (OH), carboxyl (COOH), sulfonic acid group (SO₃H) and zwitterionic sulfobetaine group (^⊕N((CH₃)₂)(CH₂)₃SO₃^⊖) with controllable wettability were prepared by UV radiation grafting vinyl monomers with these functional groups. Our results emphasized that both surface functional groups and surface wettability had significant effects on the adhesion of leukocyte and platelet. In the case of filter materials with the same wettability, leukocytes adhering to filter materials decreased in the order: the surface bearing OH only>the surface bearing both OH and COOH>the surface bearing sulfobetaine group>the surface bearing SO₃H, while platelets adhering to filter materials decreased as the following order: the surface bearing SO₃H>the surface bearing both OH and COOH>the surface bearing OH only>the surface bearing sulfobetaine group. As the wettability of filter materials increased, both leukocyte and platelet adhesion to filter materials declined, except that leukocyte adhesion to the surface bearing OH only remained unchanged.

Keywords: Functional groups; Wettability; Leukocyte; Platelet; Adhesion

Multifractal analysis of the tensile fracture morphology of polyvinylidene chloride/glass fiber composite by Yong-Hai Zhang; Bao-Feng Bai; Jian-Qiang Li; Jing-Bo Chen; Chang-Yu Shen (pp. 2984-2989).

▶ The fracture surfaces for PVDC/GF composite were analyzed by multifractal formalism. ▶ It shows that the morphology is dependent on the mechanical properties. ▶ The multifractal spectrum could characterize this relationships quantitatively. ▶ Also, the tensile fracture is the result of the competition between ductile and brittle fracture.In the present work, the building panel of glass fiber reinforced polyvinylidene chloride composite was prepared and the tensile fracture surfaces of the composites were investigated by the box-counting method of multifractal theory. It suggested that the tensile fracture surface of polyvinylidene chloride/glass fiber (PVDC/GF) composite exhibits multifractal features and the tensile fracture surface morphology of the composite have a strong dependence on the mechanical properties. The results showed that the variation of glass fiber content would lead to the change of mechanical properties, which were responsible for the tensile fracture morphology of PVDC/GF composite. Consequently, the gray value distribution characterizing the surface morphology on the tensile fracture surface would become more non-uniform or less due to this change. The multifractal spectrum could correspondingly mirror this variation according to multifractal methodology. It indicated that the width in multifractal spectrum is sensitive to the morphology of the tensile fractured surface. It is concluded that the multifractal spectrum is the result of the change in mechanical properties of the composites. Additionally, it also suggested that the tensile fracture of the composite is the result of the competition between ductile fracture and brittle fracture by comparing the multifractal spectra and the multifractal spectra would correspondingly change due to this competition. The more the percentage of ductile fracture is, the more rough the fracture surface, the larger the width in the multifractal spectrum. Therefore, it is thought that the multifractal spectrum could feature the rough morphology of the tensile fractured surface and the mechanical properties quantitatively.

Keywords: Multifractal spectrum; PVDC; Morphology; Mechanical property; Fracture process

Epitaxial growth of titanium oxycarbide on MgO (001) substrates by pulsed laser deposition by Hien Do; Tzu-Chun Yen; Chih-Sheng Tian; Yue-Han Wu; Li Chang (pp. 2990-2994).

▶ High-quality epitaxial TiC_xO_y films are successfully grown on MgO (001) substrates. ▶ The stoichiometry of TiC_xO_y is about x∼0.47 and y∼0.69. ▶ The TiC_xO_y film is electrically conducting with resistivity of 137μΩcm.Epitaxial TiC_xO_y thin films were grown on MgO (001) substrates by using pulsed laser deposition method. High-resolution X-ray diffraction and transmission electron microscopy were used to examine crystallinity and microstructure of epitaxial TiC_xO_y film on MgO. The chemical composition of the film is determined to be x∼0.47 and y∼0.69 by X-ray photoelectron spectroscopy. Atomic force microscopy revealed that the surface of TiC_xO_y film is very smooth with roughness of 0.18nm. The resistivity of the TiC_xO_y film measured by four-point-probe method was about 137μΩcm.

Keywords: Titanium oxycarbide; Epitaxial growth; Pulsed laser deposition

Novel tantalum based photocurable hybrid sol–gel material employed in the fabrication of channel optical waveguides and three-dimensional structures by M. Oubaha; R. Copperwhite; A. Gorin; V. Purlys; C. Boothman; M. O'Sullivan; R. Gadonas; C. McDonagh; B.D. MacCraith (pp. 2995-2999).

▶ In this study we have developed for the first time photocurable hybrid organosiloxane-tantalum based materials. ▶ The structuration of this material employing both single photon and two-photon polymerisation techniques allowed the fabrication of non-shrinking planar and three-dimensional structures. ▶ The optical losses at the telecommunication wavelengths in the fabricated waveguides have been measured to be significantly lower than similar materials due to the peculiar high condensation of this material, leading to low absorbing hydroxyl groups.A novel hybrid organic–inorganic photocurable sol–gel material based on tantalum ethoxide and 3-trimethoxysilylpropylmethacrylate has been developed, characterised and used in the fabrication of optical waveguides and three-dimensional woodpile structures employing the single and two-photon polymerisation techniques, respectively. Single mode waveguides operating at 1310 and 1550nm have been fabricated, optically characterised and their performances correlated to the material formulation. Three-dimensional woodpile structures exhibiting negligible shrinkage have been developed and their remarkable mechanical stability correlated to the molecular structure of the hybrid material. The overall fabrication process of these devices is described and it is shown that the refractive indices of the materials can be tailored by a precise control of the material composition allowing the successful fabrication of performing single mode waveguides.

Keywords: Hybrid sol–gel materials; Waveguides; Photonic; Three-dimensional photonic crystal

A first-principles calculation on the electronic properties of Si/N-codoped TiO₂ by Weimei Shi; Qifeng Chen; Yao Xu; Dong Wu; Chunfang Huo (pp. 3000-3006).

The doping atom location has effect on the electronic structures of Si/N-codoped TiO₂. ▶ Replacing O atom with N atom and replacing the adjacent Ti atom with Si atom, TiO₂ has the smallest defect formation energy and band gap. ▶ In Si/N-codoped TiO₂, the hybridization between impurity states and O-2p states could enhance the lifetime of photo-generated holes and change some unoccupied N-2p states to occupied states.To deeply understand the effects of Si/N-codoping on the electronic structures of TiO₂ and confirm their photocatalytic performance, a comparison theoretical study of their energetic and electronic properties was carried out involving single N-doping, single Si-doping and three models of Si/N-codoping based on first-principles. As for N-doped TiO₂, an isolated N 2p state locates above the top of valence band and mixes with O 2p states, resulting in band gap narrowing. However, the unoccupied N 2p state acts as electrons traps to promote the electron–hole recombination. Using Si-doping, the band gap has a decrease of 0.24eV and the valence band broadens about 0.30eV. These two factors cause a better performance of photocatalyst. The special Si/N-codoped TiO₂ model with one O atom replaced by a N atom and its adjacent Ti atom replaced by a Si atom, has the smallest defect formation energy in three codoping models, suggesting the model is the most energetic favorable. The calculated energy results also indicate that the Si incorporation increases the N concentration in Si/N-codoped TiO₂. This model obtains the most narrowed band gap of 1.63eV in comparison with the other two models. The dopant states hybridize with O 2p states, leading to the valence band broadening and then improving the mobility of photo-generated hole; the N 2p states are occupied simultaneously. The significantly narrowed band gap and the absence of recombination center can give a reasonable explanation for the high photocatalytic activity under visible light.

Keywords: Si/N-codoping; First-principles; Electronic properties

Probing buried interfaces on Ge-based metal gate/high-k stacks by hard X-ray photoelectron spectroscopy by J. Rubio-Zuazo; E. Martinez; P. Batude; L. Clavelier; A. Chabli; G.R. Castro (pp. 3007-3013).

▶ A thin Si interlayer prevents the oxidation of the substrate in Ge based metal-gate/high-k stacks. ▶ Hard X-ray photoelectron spectroscopy enables a non-destructive analysis of interfaces buried several nanometers. ▶ A Hf silicate is formed at the interface between HfO₂ and SiO₂.In this contribution, we present results of a non-destructive in-depth analysis of concentration of chemical components at buried interfaces on Ge-based CMOS by means of hard X-ray photoelectron spectroscopy (HAXPES) and low angle X-ray reflectivity (XRR). Two samples composed of a Ge/Si/SiO₂/HfO₂/TiN stack, with layer and interlayer thicknesses of 2500, 0.9, 0.5, 4.9, 3.4nm and 2500, 0.7, 1, 5.8, 3nm have been studied. The use of electrons with kinetic energies from few eV up to 15keV enables to tune the information depth being able to analyze the desired interface in a non-destructive way. XRR enables the determination of the exact layer thickness and density. The results suggest that the Si interlayer prevents the Ge oxidation. Depth profiles of the electronic structure have been obtained for both samples by following the evolution of the photoemission signal from the Hf 2p_3/2 core level as a function of the photoelectron kinetic energy. The depth profile of the electronic structure reveals the presence of a chemical shift of the Hf 2p_3/2 core level, which is related to an interfacial bonding state. Our results demonstrate the excellent capability of HAXPES to study buried interfaces in a non-destructive way.

Keywords: PACS; 85.30.De; 85.30.−z; 73.40.Qv; 79.60.−I; 79.60.Jv; 73.21.Ac; 72.15.Lh; 71.30.+hHAXPES; CMOS devices; Ge-based metal gate/high-k stacks

Initial growth of intrinsic microcrystalline silicon thin film: Dependence on pre-hydrogen glow discharge and substrate surface morphology by Xiaodan Zhang; Xinxia Zheng; Guanghong Wang; Ying Zhao (pp. 3014-3019).

Display Omitted▶ Pre-hydrogen glow discharge decreases amorphous incubation volume. ▶ Pre-hydrogen glow discharge increases the nuclei density. ▶ Substrate surface morphology affects the formation of crystalline.We found the decreases of amorphous incubation volume from Raman spectra and surface roughness from AFM in hydrogenated microcrystalline silicon (μc-Si:H) films deposited with a pre-hydrogen glow discharge. The above phenomena are attributed to the increase in the nuclei density as observed by AFM measurements. Substrate surface morphology of eagle2000 glass modified by wet etching also has a positive effect on the nucleation and crystalline formation. In addition, μc-Si:H doped layer is also beneficial for decreasing the amorphous incubation layer thickness because of surface roughness and crystallinity in the μc-Si:H doped layer.

Keywords: Nucleation; Substrate surface morphology; Pre-hydrogen glow discharge

Polyurethane nanofibers containing copper nanoparticles as future materials by Faheem A. Sheikh; Muzafar A. Kanjwal; Saurabh Saran; Wook-Jin Chung; Hern Kim (pp. 3020-3026).

▶ This work reports a novel approach to fabricate polyurethane nanofibers containing copper nanoparticles for the application in filtration purposes. A simple method, by using electrospinning had been exploited to form the nanofibers. The nanofibers can easily trap copper nanoparticles with them during the electrospinning process. These fibers do exhibit good characteristics of nanofibrous form, without any structural defects. The nanofibers can be characterized by various states of art techniques, which indicate the future use of these nanofibers in various kinds of filtration process.In the present study, we aimed to represent a novel approach to fabricate polyurethane nanofibers containing copper nanoparticles (NPs) by simple electrospinning process. A simple method, not depending on additional foreign chemicals, has been employed to utilize prepared copper NPs in polyurethane nanofibers. Typically, a colloidal gel consisting of copper NPs and polyurethane has been electrospun. SEM-EDX and TEM results confirmed well oriented nanofibers and good dispersion of pure copper NPs. Copper NPs have diameter in the range of 5–10nm. The thermal stability of the synthesized nanofibers was examined for identifying the proper settlement of copper NPs among the nanofibers, according to the concentrations used in original solutions. Furthermore, XRD results well demonstrated crystalline feature of copper NPs. Model microorganisms Escherichia coli and Bacillus subtillus had been used to check the antimicrobial efficacy of these nanofiber mats. Subsequently, antimicrobial tests have indicated that the prepared nanofibers do posses good bactericidal effect. Accordingly, it is noted that the obtained nanofiber mats can be used as future filter membranes with good antimicrobial activities.

Keywords: Antimicrobial; Polyurethane; Copper; Nanoparticles and Nanofibers

Wetting behavior of high energy electron irradiated porous superhydrophobic silica films by A. Venkateswara Rao; Sanjay S. Latthe; Charles Kappenstein; V. Ganesan; M.C. Rath; Shilpa N. Sawant (pp. 3027-3032).

▶ Porous morphology of pristine film was changed to compact after electron irradiation. ▶ The water drops roll off on the pristine film and sticks to the irradiated film. ▶ Wetting behavior of silica films was changed due to high energy electron irradiation.The nature of adhesive forces between water and hydrophobic materials has been a subject of great interest. The influence of high energy electron irradiation (7MeV) on wetting behavior of superhydrophobic silica films has been investigated. The results of surface morphological study suggest that the porous morphology of pristine (non-irradiated) silica film was changed to compact morphology after electron irradiation (of energy 7MeV). The experiments showed that a gradual decrease in static water contact angle (SWCA); whereas an abrupt increase in water sliding angle (WSA) of irradiated silica film. The water droplets easily roll off on the pristine silica films, whereas the water droplet does not slide on the irradiated silica film surface even when the surface is tilted vertically or turned upside down. We characterized the pristine and irradiated silica films by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and static and dynamic water contact angle measurements.

Keywords: Surfaces and interfaces; Sol–gel processes; Liquid–solid reactions; Superhydrophobic

Improved color purity and electroluminescent efficiency obtained by modulating thicknesses and evaporation rates of hole block and electron transport layers by Liang Zhou; Ruiping Deng; Jing Feng; Xiaona Li; Xiyan Li; Hongjie Zhang (pp. 3033-3038).

▶ Injection and transport of electrons decreases gradually with increasing thicknesses. ▶ Injection and transport of electrons decreases gradually with increasing evaporation rates. ▶ An efficient approach to suppress the EL originate from hole block material. ▶ Moderate decrease of electron transport facilitates the balance of holes and electrons.In this work, a series of electroluminescent (EL) devices based on trivalent europium (Eu³⁺) complex Eu(TTA)₃phen (TTA=thenoyltrifluoroacetone, phen=1,10-phenanthroline) were fabricated by selecting 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) and tris(8-hydroxyquinoline) aluminum (Alq₃) as hole block and electron transport materials, respectively. Interestingly, we found the transport of electrons decreases gradually with increasing thicknesses and evaporation rates of BCP and Alq₃ layers. Analyzing carrier distribution and EL spectra, we conclude that appropriately modulating the thicknesses and evaporation rates is an efficient way to decrease the accumulation of electrons in HBL, thus suppressing the EL of hole block material. On the other hand, decreasing the transport of electrons can also facilitate the balance of holes and electrons on Eu(TTA)₃phen molecules, thus further enhancing the EL efficiency. As a result, pure Eu³⁺ emission with the efficiency as high as 8.49cd/A was realized by controlling the thicknesses and evaporation rates of BCP and Alq₃ layers to be 30nm and 0.10nm/s, 40nm and 0.10nm/s, respectively.

Keywords: PACS; 73.40.−c; 85.60.JbColor purity; Electron accumulation; Hole penetration; Recombination zone

Photochromic and electrochromic performances of new types of donor/acceptor systems based on crosslinked polyviologen film and electron donors by Li-ping Gao; Guo-jing Ding; Chao-long Li; Yue-chuan Wang (pp. 3039-3046).

▶ Viologen-functionalized methacrylate and styrene copolymer, COPV⁺², was prepared and cross-linked through the condensation of the siloxane groups on the methacrylate units. ▶ The donor/acceptor system composed of COPV⁺² and hydroxyethylferrocene (HEFc) showed both photo- and electrochromism. ▶ The photo- and electrochromic performances of COPV⁺²/HEFc and COPV⁺²/phenylenediamine were comparatively studied. ▶ HEFc exhibited the similar ability in electronic donating as phenylenediamine for Viologens in photo- and electrochromism.Viologen-functionalized copolymer COPV²⁺ was synthesized by copolymer graft-modified, which was crosslinked by NH₃·H₂O gas-fumigated at 25°C for 4h due to the condensation of the siloxanes of COPV²⁺ film. Simultaneously, different donor/acceptor systems had been prepared based on crosslinked polyviologen film (COPV²⁺) and N,N,N′,N′-tetramethyl-1,4-phenylenediamine (TMPD) or hydroxyethylferrocene (HEFc) in order to shorten the response times and improve contrast ratios in response to external photo- and potential stimuli. The evolution of structures from COPO to COPV²⁺ is carefully characterized. The COPV²⁺/TMPD and COPV²⁺/HEFc films exhibited both photochromic and electrochromic performances. After UV irradiations, COPV²⁺/TMPD and COPV²⁺/HEFc films changed their colors from colorless to deep blue, while optical transmissions at 610nm decreased about 64% and 75%, respectively. When removing out from UV irradiation, the colored COPV²⁺/TMPD and COPV²⁺/HEFc films faded to the original colors within about 60min. When COPV²⁺/TMPD and COPV²⁺/HEFc films were biased with negative voltage of −2.5V, they changed their colors from colorless to deep blue in 4s and 3s, while the optical transmissions at 556nm decreased about 81% and 75%, respectively. When electric impulse was switched off, the colored COPV²⁺/TMPD and COPV²⁺/HEFc films faded to the original colors within about 7s and 6s, respectively.

Keywords: Photochromism; Electrochromism; Crosslinked polyviologen film; Donor/acceptor system

Structural and electronic properties of atomic oxygen adsorption on Pt(111): A density-functional theory study by Qing Pang; Yan Zhang; Jian-Min Zhang; Ke-Wei Xu (pp. 3047-3054).

▶ The fcc site is more stable site than the hcp site for oxygen adsorption. ▶ The adsorption energy decreases with increasing oxygen coverage. ▶ The oxygen-induced lateral relaxations and bucklings are in the outermost Pt layers. ▶ The O-Pt chemical bond shows some degree of both ionic and covalence characters. ▶ With increasing oxygen coverage, the metallic characters of O/Pt(111) are weakened.By using the density-functional theory, we have systematically investigated the adsorption of oxygen on Pt(111) surface for a wide range of coverages (from 0.11ML to 1.00ML) and adsorption sites. In the view of adsorption energy maximization, we found that the fcc site is the most stable site for oxygen adsorption, which is always slightly energetically favorable than the hcp site, and for these two sites, the adsorption energies decrease as the increasing oxygen coverage due to the increasing repulsive lateral interactions in the overlayer O adatoms. Except for coverage of 1.00ML, the oxygen-induced lateral relaxations and bucklings are found in the outermost substrate Pt layers. Taking into account the effects of the chemical environment as a function of the relative richness in oxygen, we obtained that oxygen can form two stable configurations in the fcc site adsorption: the 0.25ML configuration in oxygen-poor conditions, and the 0.50ML case in oxygen-rich environments. The work function and the surface dipole moment are also studied and analyzed. Electron transfer between the first layer Pt and the O adatoms indicates the O–Pt chemical bond shows some degree of ionic character. In addition, the hybridization between O 2p and Pt 5d orbitals, especially at oxygen coverage of 1.00ML, implies the O–Pt bond also shows some degree of covalence character. Moreover, with the increasing oxygen coverage, more Pt 5d states are empty thus weakening the binding of O/Pt(111) systems at higher coverage, and the density of states at the Fermi level for the O/Pt(111) system decreases thereby the metallic character is weakened.

Keywords: Density-functional theory; Adsorption; Relaxation; Electronic structures

Mechanisms for nano particle removal in brush scrubber cleaning by Yating Huang; Dan Guo; Xinchun Lu; Jianbin Luo (pp. 3055-3062).

▶ A model is presented to describe the nano particle (<100nm) removal behavior in brush scrubber cleaning. The forces on the particles in different situations are analyzed and discussed. ▶ Some cleaning experiments are carried out to evaluate the cleaning effect in the industry product line. The results are agreed with our model. So the model in our research can be used to predict the particle residua and help optimizing the cleaning parameter.A model describing the nano particle (<100nm) removal behavior in brush scrubber cleaning is presented based on experiment results and theoretical analysis. The forces on the particles in different situations are analyzed and discussed. The adhesion forces of the van der Waals force, the electrostatic force, the brush load and the static friction between the particle and the wafer are calculated. The contact elastic force, hydrodynamic drag force and friction between the brush and the particle are considered as removal forces and are evaluated. The porous structure and roughness surface of brush material are considered in the hydrodynamic model to describe the brush deformation and the flow field in the cleaning process. The porous structure will result in decrease of hydrodynamic drag force. There are four situations of the particles relative to the brush roughness asperities for which the forces on the particle are different. When the particle is in contact with a brush asperity or on the wafer surface and in a semi-infinite fluid flow field, the particle may be removed by hydrodynamic force and elastic force in the presence of surfactant. When the particle is embedded in the brush asperity, the remove will realized when the friction caused by adhesion between the brush and the particle overcome the adhesion force between particle and wafer surface. The removed particles will be in the flow field or adhered on the brush surface and may redeposit on the wafer surface.

Keywords: Brush-scrub; Post CMP cleaning; Particle removal; Hydrodynamics

Fabrication of nano-electrode arrays of free-standing carbon nanotubes on nano-patterned substrate by imprint method by W.S. Chang; J.W. Kim; D.G. Choi; C.S. Han (pp. 3063-3068).

The synthesis of isolated carbon nanotubes with uniform outer diameters and ordered spacing over wafer-scale areas was investigated for fabrication of nano-electrode arrays on silicon wafers for field emission and sensor devices. Multi-walled carbon nanotubes (MWCNTs) were grown on TiN electrode layer with iron catalyst patterned by nano-imprint lithography (NIL), which allows the precise placement of individual CNTs on a substrate. The proposed techniques, including plasma-enhanced chemical vapor deposition (PECVD) and NIL, are simple, inexpensive, and reproducible methods for fabrication of nano-scale devices in large areas. The catalyst patterns were defined by an array of circles with 200nm in diameter, and variable lengths of pitch. The nano-patterned master and Fe catalyst were observed with good pattern fidelity over a large area by atomic force microscope (AFM) and scanning electron microscopy (SEM). Nano-electrodes of MWCNTs had diameters ranging from 50nm to 100nm and lengths of about 300nm. Field emission tests showed the reducing ignition voltage as the geometry of nanotube arrays was controlled by catalyst patterning. These results showed a wafer-scale approach to the control of the size, pitch, and position of nano-electrodes of nanotubes for various applications including electron field-emission sources, electrochemical probes, functionalized sensor elements, and so on.

Keywords: Nano-electrode; Nano-imprint; Carbon nanotube; Plasma-enhanced chemical vapor deposition; Patterning

Substrate-temperature dependent structure and composition variations in RF magnetron sputtered titanium nitride thin films by K. Vasu; M. Ghanashyam Krishna; K.A. Padmanabhan (pp. 3069-3074).

▶ Deposition of TiN films by RF magnetron sputtering in 100% nitrogen atmosphere is demonstrated. ▶ Nitrogen stoichiometry in the films is shown to be substrate temperature dependent. ▶ Photluminescence is observed. ▶ Optical constants in the UV-visible and NIR region are reported.Using RF reactive magnetron sputtering process in a 100% nitrogen atmosphere, TiN_x thin films were deposited on a quartz substrate. The crystal structure and optical properties of the as-deposited thin films, as a function of substrate temperature, were studied. From room temperature till 600°C, with increasing temperature, the crystal structure changed from tetragonal to cubic, with ‘ x’ in TiN_x increasing with the substrate temperature. In the entire temperature range x was less than 1. Simultaneously, the optical plasma band of the film shifted from the ultra-violet region having energy of 4.83eV to the visible region corresponding to energy of 2.47eV. The width of the transmittance band in the visible range varied with temperature between 460nm and 620nm. All the films exhibited a PL (photoluminescent) single band in the middle of the visible region.

Keywords: Thin films; Magnetron sputtering; Titanium nitride; Stoichiometry; Optical properties

Thickness dependent physical and photocatalytic properties of ITO thin films prepared by reactive DC magnetron sputtering by K. Jagadeesh Kumar; N. Ravi Chandra Raju; A. Subrahmanyam (pp. 3075-3080).

Transparent and conducting indium tin oxide (ITO) thin films were deposited on glass substrates by reactive DC magnetron sputtering at room temperature. The effect of thickness (165–1175nm) on the physical (structural, optical, electrical) and photo catalytic properties of ITO thin films were investigated systematically. It is observed that with increasing thickness (i) the films turn from amorphous to polycrystalline with a preferential orientation along (440) direction, (ii) the average grain size and RMS roughness increases from 35nm to 100nm and 2.3nm to 8.6nm respectively, (iii) the optical band gap decreases from 3.65eV to 3.45eV and (iv) the relative density (calculated from the refractive index data) decreases. Four probe and Hall effect measurements show a low resistivity (4.5×10⁻⁴Ωcm), mobility (26cm²/Vs) and high carrier concentration (5.3×10²⁰cm⁻³) values for film with a thickness 545nm. The work function of ITO films measured by Kelvin probe method varies with thickness. The photocatalytic activity (PCA) of ITO thin films was studied by the degradation of Rhodamine B in water; highest PCA is shown for the films of 545nm thickness. Present work shows that the ITO is a promising photocatalytic material for the degradation of organic compounds.

Keywords: ITO thin films; Magnetron sputtering; Photocatalysis; Thickness; Work function

Ultraviolet laser interference patterning of hydroxyapatite surfaces by Jana Berger; Marzellus Grosse Holthaus; Nicola Pistillo; Teja Roch; Kurosch Rezwan; Andrés Fabián Lasagni (pp. 3081-3087).

▶ In this paper, we have applied the method of direct laser interference patterning to produce periodic patterns on hydroxyapatite, using UV ration (266 and 355nm). Line- and cross-like patterns with periodical distances of 10 and 20μm were fabricated with different energy densities as well as pulse numbers. ▶ The results here presented show an alternative route for the direct fabrication of micro patterns on ceramics. Compared to other techniques such Aerosol-Jet-printing or microcontact printing, only one step is necessary to fabricate the micropatterns, and high fabrication speeds, even on non-planar substrates, can be achieved.Direct laser interference patterning (DLIP) was used to produce periodic patterns on hydroxyapatite. A Nd:YAG laser operating at 266 and 355nm wavelengths and a pulse duration of 10ns was used in these experiments. Line- and cross-like patterns with periodical distances of 10 and 20μm were fabricated with energy densities between 0.6 and 2.4J/cm², and pulse numbers from 1 to 100. In the low/middle laser intensity range it was observed that the structure depth increased with the pulse number. However, for higher energies the patterns smudge due to thermal effects. For single pulse laser experiments, increasing of the laser fluence did not produce deeper structures. In addition, the best results were obtained when using low-medium laser intensities (∼0.6–1.2J/cm²) and moderate number of laser pulses (20–50), depending on laser wavelength. In addition, at a 355nm wavelength only patterns with 20μm periods presented a good quality structure. In contrast, 266nm wavelengths permitted to improve resolution up to periods of 10μm due to a higher photochemical contribution to the ablation process. X-ray Photoelectron Spectroscopy (XPS) analysis showed that there are no significant changes in the chemical composition of laser-treated hydroxyapatite.

Keywords: Calcium phosphate; Hydroxyapatite; Micropatterning; Surface texture; Surface treatment

Effects of oxygen plasma treatment on the dielectric properties of Ba_0.7Sr_0.3TiO₃ thin films by Lefan Tan; Niandeng Xiong (pp. 3088-3091).

▶ This manuscript contains new work related to improving the performance of the oxide thin films. ▶ Our experiments indicate that the oxygen plasma treatment condition of 200W, 3Torr and 5min is optimized for BST thin films. ▶ The loss tangent of the plasma treated films decreased to 0.7% and leakage current density decreased by two orders of magnitude, as compared to that of the as-deposited films.Barium strontium titanate (BST) films prepared by RF magnetron sputtering were processed in an O₂-plasma treatment system. Experiment results indicate that the leakage current and dielectric loss of the films were effectively reduced after plasma treatment. The possible mechanism may be attributed to the passivation of oxygen vacancies, which act as electric conduction paths of leakage current. The effects of the time, power and O₂-plasma pressure of oxygen plasma treatment on the dielectric properties of BST thin films were further investigated and optimized. Compared to as-deposited films, the BST films treated in oxygen plasma for 5min, 200W and 3Torr demonstrated reduced loss tangent around 0.7% and leakage current density of 7.96×10⁻⁹A/cm². However, it was also found that excessive plasma treatment would affect the dielectric properties of BST films negatively.

Keywords: BST; Oxygen plasma treatment; Dielectric property; Leakage current

Anodic-hydrothermal preparation of prism-shaped CaTiO₃ structure on titanium surface by Fen Zhang; Shougang Chen; Chan Lin; Yansheng Yin (pp. 3092-3096).

▶ We report a simple method to synthesize 3D rectangular prism-shaped CaTiO₃ structures via an in situ hydrothermal reaction under different conditions on the titania/titanium substrates for the first time. ▶ The TEM image of the as-prepared CaTiO₃ structure possesses a beautiful rectangular prism-shaped structure. ▶ The results show that the obtained CaTiO₃ structures have high induction capability for the nucleation and growth of biomimetic apatite in SBF.The prism-shaped perovskite structure of CaTiO₃ on titanium surface was fabricated by an anodic-hydrothermal method. Firstly, the TiO₂ film was formed on Ti substrate by electrochemical anodization. Secondly, the anodized TiO₂/Ti substrate was used as a template for the hydrothermal synthesis of CaTiO₃ coating. The samples were characterized with X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectrum. The experimental results show that anodic TiO₂ substrate and alkali environment are key factors for the formation of prism-shaped CaTiO₃, and the NaOH concentrations plays an important role in determining the size and shape of CaTiO₃ structures. Meanwhile, the CaTiO₃ surfaces possess the better deposition ability of Ca and P in vitro.

Keywords: Anodic-hydrothermal; CaTiO; ₃; Structure; Nanomaterials

Post-heat treatment of arc-sprayed coating prepared by the wires combination of Mg-cathode and Al-anode to form protective intermetallic layers by Rongzheng Xu; Gang Song (pp. 3097-3102).

▶ The Al–Mg composite coating could be prepared using a simple electric arc spraying process with the wires combination of Mg-cathode and Al-anode. However, the coatings are just mechanically mixed with the components of individual Mg and Al wires. ▶ After PHT for 4h at 430°C, the Al–Mg composite coating on the Mg-steel weld joint appears diffusion reaction and forms the intermetallic compounds that is mainly composed of Al₃Mg₂ and Al₁₂Mg₁₇. ▶ The mircohardness (about 220 HV_0.05) of the coating increases significantly after post-heat treatment.A Mg–Al intermetallic compounds coating was prepared on the surface of Mg-steel lap joint by arc-sprayed Al–Mg composite coating (Mg-cathode and Al-anode) and its post-heat treatment (PHT). The effect of PHT temperature on the phase transition, microstructure and mechanical properties of the coating was investigated by X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscopy, optical microscope and microhardness test. The result shows that the intermetallic compounds layer that is mainly composed of Al₃Mg₂ and Mg₁₇Al₁₂ is formed by the self-diffusion reaction of Mg and Al splats in the coating after PHT for 4h at 430°C.

Keywords: Intermetallics compounds coating; Arc spray processing; Post-heat treatment; Diffusion

Study of laser-induced breakdown spectroscopy to discriminate pearlitic/ferritic from martensitic phases by Shunchun Yao; Jidong Lu; Kai Chen; Shenghua Pan; Junyan Li; Meirong Dong (pp. 3103-3110).

▶ Laser-induced breakdown spectroscopy technique is used to discriminate the microstructure of steel samples. ▶ The ablated volume of pearlite/ferrite is distinctly larger than that of martensite. ▶ There is no significant difference between the plasma temperature of pearlite/ferrite and that of martensite. ▶ PCA can be used to separate the plasma spectra of pearlite/ferrite and martensite.The 20G steel has been widely used for boiler heat exchange surface. In this paper, we use laser-induced breakdown spectroscopy to analyze steel samples with different microstructures. The plasma parameters (e.g. line intensity, temperature, and ablated crater) of different microstructures have been studied and compared with each other. Our results reveal that the difference of ionic Fe lines is more obvious than atomic Fe lines between pearlite/ferrite and martensite. The ablated volume of pearlite/ferrite is distinctly larger than that of martensite, whereas there is no significant difference between the plasma temperature of pearlite/ferrite and that of martensite. Additionally, we employ principal component analysis method to differentiate these samples, and study the performance of different wavelength ranges (200–290nm, 288–393nm and 391–480nm). The results show that the plasma spectra of pearlite/ferrite and martensite can be separated completely by PC1 in the range of 200–290nm. The investigations indicate that LIBS may be applied not only as an elemental analytical technique but also a new way to determine the microstructure changes of steel samples.

Keywords: Laser-induced breakdown spectroscopy (LIBS); Microstructure; Plasma parameters; Principal component analysis (PCA)

Development of nano TiO₂-incorporated phosphate coatings on hot dip zinc surface for good paintability and corrosion resistance by S.M.A. Shibli; Francis Chacko (pp. 3111-3117).

Phosphating is one of the most important chemical conversion processes for the purpose of corrosion protection and primer for painting. In the present work, nano TiO₂ incorporated phosphate coating was developed on hot dip galvanized zinc surface for achieving good paintability and corrosion resistance. Based on the results from preliminary studies, the amount of nano TiO₂ incorporated into the phosphating bath was optimized as 0.1g. TiO₂ incorporation effectively reduced the extent of zinc dissolution during phosphating and activated the process to achieve the expected coating weight faster. Also it yielded coating with greater thickness than the normal phosphate coating. The TiO₂ incorporation resulted in a well crystallized phosphate coating with large crystal size and greater surface coverage. Results from the electrochemical analysis revealed the better barrier protection characteristics and enhanced corrosion resistance of TiO₂ incorporated phosphate coatings over the normal phosphate coatings.

Keywords: Key words; Zinc coating; Galvanization; Corrosion; Polarization; Impedance; Barrier protection; Phosphating

Effect of focusing conditions on synthesis of titanium oxide nanoparticles via laser ablation in titanium–water interface by A. Nath; S.S. Laha; A. Khare (pp. 3118-3122).

▶ TiO_x ( x=1.5, 2) nanoparticles are synthesized via laser ablation in titanium-water interface. ▶ The laser focusing conditions are varied. ▶ Tight focusing led to rutile phase of TiO₂. ▶ Defocused condition resulted in anatase phase of TiO₂.Pulsed laser induced breakdown of a titanium target in water medium is carried out to synthesize TiO_x ( x=1.51, 2) nanoparticles. The focusing condition of the source laser was varied and its potential effect onto the size and structural phases of the nanoparticles are reported. Under tightly focused condition, high temperature and high pressure plasma led to formation of rutile TiO₂ whereas at regions of low pressure and low temperature plasma, anatase TiO₂ was formed. In addition, oxygen deficient TiO_1.51 was also formed for all the focusing condition due to the transient plasma quenching induced by pulsed source laser. Some studies onto the optical properties of the colloidal solution containing TiO_x nanoparticles are also performed.

Keywords: Metal oxide nanoparticles; TiO; ₂; nanoparticles; Anatase TiO; ₂; Rutile TiO; ₂; Laser induced water plasma; Transient plasma; Focusing effect; Laser ablation in water

Synthesis of single-walled carbon nanotubes with selective diameter distributions using DC arc discharge under CO mixed atmosphere by Yanjie Su; Zhi Yang; Hao Wei; Eric Siu-Wai Kong; Yafei Zhang (pp. 3123-3127).

▶ SWCNTs with selective diameters can be synthesized by DC arc-discharge method under the mixed gases of CO and helium. ▶ Appropriate CO pressure (>8kPa) results in the diameter selective growth of SWCNTs. ▶ Pure CO as buffer gas will result in the formation of carbon nanoparticles.Diameter selective growth of single-walled carbon nanotubes (SWCNTs) is one of the most important challenges for the application of SWCNTs in future high-performance nanodevices. In this investigation, SWCNTs with selective diameters have been synthesized by DC arc discharge method, in which carbon monoxide (CO) mixed with helium were used as buffer gases. The experimental results show that SWCNTs with small diameters are preferentially etched with the increase of CO concentration. However, pure CO as buffer gas can result in the formation of carbon nanoparticles. Appropriate CO pressure (>8kPa) gives the diameter selective growth of SWCNTs in the range of 1.5–1.7nm.

Keywords: Single-walled carbon nanotubes; Carbon monoxide; Arc discharge; Narrow diameters distribution

Phospholipid-driven long-range ordering of Fe₃O₄ nanoparticles by Jung Hoon Kim; Ah-Young Song; Dae Hoon Kwon; Hyeun Hwan An; Hyung Soo Ahnn; Young-Keun Kim; Chong Seung Yoon (pp. 3128-3134).

1,2-Dioleoyl-3-trimethylammonium-propane (DOTAP) phospholipid membrane was used to produce a two-dimensional array of tightly packed Fe₃O₄ nanoparticles.Display Omitted▶ Fe₃O₄ nanoparticles were encapsulated with DOTAP molecules. ▶ Spin-coating was used to self-assemble the encapsulated Fe₃O₄ nanoparticles. ▶ The self-assembled particles formed a monolayer.N-(1-(2,3-dioleoyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTAP) lipid molecules were used to drive the self-assembly of pre-fabricated Fe₃O₄ nanoparticles (∼10nm in size) into a tightly packed hexagonal array by spin coating. In spite of the relatively wide particle size distribution of the pre-fabricated nanoparticles, the nanoparticles encapsulated by the DOTAP lipid molecules were self-assembled into a two-dimensional superlattice over a large area because the monolayer of DOTAP molecules attached to the particles surface provided the force necessary to anchor the nanoparticles on the substrate surface during spin coating as well as the force necessary to hold the particles together. It is expected that the proposed method can be easily scalable to an industrial process and be also adapted to different nanoparticle systems by appropriate selection of the encapsulating lipid molecules.

Keywords: Phospholipid; Fe; ₃; O; ₄; nanoparticle; Self-assembly; Spin-coating

Adhesion enhancement between electroless nickel and polyester fabric by a palladium-free process by Yinxiang Lu; Longlong Xue; Feng Li (pp. 3135-3139).

A new, efficient, palladium- and etchant-free process for the electroless nickel plating of poly(ethylene terephthalate) (PET) fabric has been developed. PET electroless plating can be prepared in three steps, namely: (i) the grafting of thiol group onto PET, (ii) the silver Ag⁰ seeding of the PET surface, and (iii) the nickel metallization using electroless plating bath. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray photoelectron spectroscopy (XPS), Raman spectrometer, X-ray diffraction (XRD), and thermogravimetric analysis (TG) were used to characterize the samples in the process, and the nickel loading was quantified by weighing. This process successfully compares with the traditional one based on KMnO₄/H₂SO₄ etching and palladium-based seed layer. The nickel coating obtained in this palladium-free process can pass through ultrasonic washing challenge, and shows excellent adhesion with the PET substrate. However, the sample with Pd catalyst via traditional process was damaged during the testing experiment.

Keywords: Polyester fabric; Palladium-free; Electroless nickel plating; Adhesion

Dependence of morphologies for SnO₂ nanostructures on their sensing property by Yu Lingmin; Fan Xinhui; Qi Lijun; Ma Lihe; Yan Wen (pp. 3140-3144).

Display Omitted▶ Three different morphologies of 1D SnO₂ nanostructures were synthesized by thermal evaporation. ▶ SnO₂ nanowires exhibited a better response and selectivity towards 500ppm ethanol. ▶ A higher sensitivity depends on large aspect ratio, good thermal stability and multimodel porosity.Different morphologies of one-dimensional (1D) SnO₂ nanocrystals were successfully synthesized by thermal evaporation method via modifying the technological parameters. The morphology and structure of crystals were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD). Gas sensors have been fabricated using the 1D SnO₂ nanocrystals to examine the responses to C₂H₅OH, CO, H₂ and CH₄ gases over a range of operating temperature from 150 to 350°C. The effect of morphologies obtained by different technological parameters on sensing property was systematically investigated. The results showed that the high sensitivity of SnO₂ nanowires was attributed to its large aspect ratio, good thermal stability and multimodel porosity.

Keywords: SnO; ₂; nanowires; Gas sensing property; Morphology

Field emission and optical properties of Ga-doped ZnO nanowires synthesized via thermal evaporation by Li Wei Chang; Jien Wei Yeh; Chia Liang Cheng; F.S. Shieu; Han C. Shih (pp. 3145-3151).

▶ Ga-doped ZnO (GZO) nanowires have been synthesized by thermal evaporation. ▶ GZO nanowires exhibit a relative weak ultraviolet emission (UV) and a strong green emission. ▶ Field emission measurements demonstrate that the GZO possess good performance.Ga-doped ZnO (GZO) nanowires have been synthesized by thermal evaporation with gallium metal as the dopant source. The morphology, microstructure and chemical composition were determined by field emission scanning electron microscopy (FE-SEM), X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS). The investigation confirmed that the GZO nanowires were the wurtzite hexagonal structures. These doped nanowires have diameters in the range 30–70nm and lengths of several hundreds of nanometers with growth direction along the (100) crystal plane. The optical properties from the cathodoluminescence (CL) and photoluminescence (PL) spectrum show that GZO nanowires exhibit a relative weak ultraviolet emission (UV) and a strong green emission. The UV emission for ZnO and GZO nanowires is attributed to near band-edge emission from recombination of free excitons. Furthermore, the green emission is attributed to oxygen vacancy and gallium impurity energy levels. Field emission measurements demonstrate that the GZO possesses good performance with a turn-on field of 3.4V/μm at a current density of 10μA/cm², a threshold field of 5.4V/μm at a current density of 1mA/cm², and a field-enhancement factor β of 5945. These results are very helpful for the design, fabrication and optimization of integrated optoelectronic nanodevices using GZO nanowires.

Keywords: PACS; 78.67.Uh; 78.67.−n; 68.37.VjNanowires; Optical properties of low-dimensional structures; Field emission

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Applied Surface Science (v.257, #7)