Check out our New Publishers' Select for Free Articles

Applied Surface Science (v.257, #8)

Editorial Board (pp. ii).

DLC nano-dot surfaces for tribological applications in MEMS devices by R. Arvind Singh; Kyounghwan Na; Jin Woo Yi; Kwang-Ryeol Lee; Eui-Sung Yoon (pp. 3153-3157).

▶ DLC nano-dot surfaces as novel tribological candidates for MEMS devices. ▶ The surfaces show reduced adhesion and friction properties at nano/micro-scales. ▶ Hydrophobicity and reduced contact area make them excellent tribological materials.With the invention of miniaturized devices like micro-electro-mechanical systems (MEMS), tribological studies at micro/nano-scale have gained importance. These studies are directed towards understanding the interactions between surfaces at micro/nano-scales, under relative motion. In MEMS devices, the critical forces, namely adhesion and friction restrict the smooth operation of the elements that are in relative motion. These miniaturized devices are traditionally made from silicon (Si), whose tribological properties are not good. In this paper, we present a short investigation of nano- and micro-tribological properties of diamond-like carbon (DLC) nano-dot surfaces. The investigation was undertaken to evaluate the potential of these surfaces for their possible application to the miniaturized devices. The tribological evaluation of the DLC nano-dot surfaces was done in comparison with bare Si (100) surfaces and DLC coated silicon surfaces. A commercial atomic force microscope (AFM) was used to measure adhesion and friction properties of the test materials at the nano-scale, whereas a custom-built micro-tribotester was used to measure their micro-friction property. Results showed that the DLC nano-dot surfaces exhibited superior tribological properties with the lowest values of adhesion force, and friction force both at the nano- and micro-scales, when compared to the bare Si (100) surfaces and DLC coated silicon surfaces. In addition, the DLC nano-dot surfaces showed no observable wear at the micro-scale, unlike the other two test materials. The superior tribological performance of the DLC nano-dot surfaces is attributed to their hydrophobic nature and the reduced area of contact projected by them.

Keywords: Nano; Micro; Adhesion; Friction; Wear; Tribology; Diamond-like carbon

The effect of oxygen-plasma treatment on Kevlar fibers and the properties of Kevlar fibers/bismaleimide composites by Min Su; Aijuan Gu; Guozheng Liang; Li Yuan (pp. 3158-3167).

▶ Oxygen-plasma treatment introduces oxygen-containing groups on the fiber surfaces. ▶ Oxygen-plasma treatment increases the surface roughness of Kevlar fibers. ▶ Treated fibers have better interfacial adhesion with resin than original fibers. ▶ Composites based on treated fibers have obviously improved integrated properties.The effect of oxygen-plasma treatment for Kevlar fibers on the interfacial adhesion and typical macro-properties of Kevlar fiber/bismaleimide composites was intensively studied. It is found that oxygen-plasma treatment significantly affects the interfacial adhesion by changing the chemistry and morphology of the surfaces of the fibers, and thus leading to improved interlaminar shear strength, water resistance and dielectric properties of the composites. However, the improvement is closely related to the treatment power and time. The best condition for treating Kevlar fiber is 70W for 5min. Oxygen-plasma treatment provides an effective technique for overcoming the poor interfacial adhesion of Kevlar fiber based composites, and thus showing great potential in fabricating high performance copper clad laminates.

Keywords: Plasma treatment; Kevlar fibers; Interfaces; Composites; Dielectric properties

Formation of carbon nanostructures containing single-crystalline cobalt carbides by ion irradiation method by Zhipeng Wang; Zamri Yusop; Pradip Ghosh; Yasuhiko Hayashi; Masaki Tanemura (pp. 3168-3173).

▶ The carbon nanofibers and nanoneedles containing cobalt carbides have been synthesized by ion irradiation method. ▶ The formation mechanism of those carbon nanostructures has been described in detail in this paper. ▶ The results are of some significant value for researchers employing ion beam-related methods to fabricate carbon nanoscales.Carbon nanofibers (CNFs) with a diameter of 17nm, and carbon nanoneedles (CNNs) with sharp tips have been synthesized on graphite substrates by ion irradiation of argon ions with the Co supplies rate of 1 and 3.4nm/min, respectively. Energy dispersive X-ray spectrometry, combined with selected area electron diffraction patterns has been used to identify the chemical composition and crystallinity of these carbon nanostructures. The CNFs were found to be amorphous in nature, while the structures of the CNNs consisted of cubic CoC_x, orthorhombic Co₂C and Co₃C depending on the cobalt content in the CNNs. The diameter of the carbide crystals was almost as large as the diameter of the CNN. Compared to the ion-induced nickel carbides and iron carbides, the formation of single-crystalline cobalt carbides might be due to the high temperature produced by the irradiation.

Keywords: Carbon nanofiber; Carbon nanoneedle; Single-crystallinity cobalt carbide; Ion irradiation

Frabicating hydroxyapatite nanorods using a biomacromolecule template by Aiping Zhu; Yan Lu; Yunfeng Si; Sheng Dai (pp. 3174-3179).

▶ In this study, we use biomacromolecule (HTCC) as a template to prepare the hydroxyapatite (HAp) with rod-like morphology. ▶ We find that the size and morphology of these HAp nanorods are able to be tailored by pH, hydrothermal synthesis temperature and the ratio of quaternary ammonium in HTCC to PO₄^3-. ▶ We prove that HTCC can be completely removed after HAp crystal formation.Rod-like hydroxyapatite (HAp) nanoparticles with various aspect ratios are synthesized by means of low-temperature hydrothermal method in the presence of a N-[(2-hydroxy-3-trimethylammonium) propyl]chitosan chloride (HTCC) template. The synthesized HAps were examined by X-ray diffraction (XRD), Fourier transform infrared spectrophotometer (FTIR) and transmission electron microscopy (TEM) techniques. The results reveal that HAps are rod-like monocrystals, where the size and morphology can be tailored by varying synthesis conditions, such as pH, hydrothermal synthesis temperature and the ratio of PO₄³⁻ to the quaternary ammonium in HTCC. The mechanism of HTCC template on HAp nanorod preparation is analyzed.

Keywords: HTCC; Hydroxyapatite; Nanorods; Template

Microstructure and tribological performance of self-lubricating diamond/tetrahedral amorphous carbon composite film by Xinchun Chen; Zhijian Peng; Xiang Yu; Zhiqiang Fu; Wen Yue; Chengbiao Wang (pp. 3180-3186).

▶ Diamond/tetrahedral amorphous carbon composite film was prepared. ▶ Self-lubricating characteristics was observed. ▶ Smoother surface and improved wear resistance were obtained.In order to smooth the rough surface and further improve the wear-resistance of coarse chemical vapor deposition diamond films, diamond/tetrahedral amorphous carbon composite films were synthesized by a two-step preparation technique including hot-filament chemical vapor deposition for polycrystalline diamond (PCD) and subsequent filtered cathodic vacuum arc growth for tetrahedral amorphous carbon (ta-C). The microstructure and tribological performance of the composite films were investigated by means of various characterization techniques. The results indicated that the composite films consisted of a thick well-grained diamond base layer with a thickness up to 150μm and a thin covering ta-C layer with a thickness of about 0.3μm, and sp³-C fraction up to 73.93%. Deposition of a smooth ta-C film on coarse polycrystalline diamond films was proved to be an effective tool to lower the surface roughness of the polycrystalline diamond film. The wear-resistance of the diamond film was also enhanced by the self-lubricating effect of the covering ta-C film due to graphitic phase transformation. Under dry pin-on-disk wear test against Si₃N₄ ball, the friction coefficients of the composite films were much lower than that of the single PCD film. An extremely low friction coefficient (∼0.05) was achieved for the PCD/ta-C composite film. Moreover, the addition of Ti interlayer between the ta-C and the PCD layers can further reduce the surface roughness of the composite film. The main wear mechanism of the composite films was abrasive wear.

Keywords: PACS; 81.05.UwSelf-lubricating; Diamond; Tetrahedral amorphous carbon; Composite film

A frequency response study of thiophene adsorption on HZSM-5 by Junling Lai; Lijuan Song; Daosheng Liu; Yucai Qin; Zhaolin Sun (pp. 3187-3191).

▶ The frequency response method is used to study adsorption of thiophene in HZSM-5. ▶ This method is effective to study two parallel adsorption processes in one system. ▶ The dynamic information and sorption sites of each adsorption process are achieved. ▶ Isotherms and Langmuir equations are used to explore adsorption mechanism.The adsorption mechanism and dynamical parameter of thiophene on HZSM-5 were studied by frequency response (FR). The FR spectra of thiophene on HZSM-5 (Si/Al=25, 38, 50) were recorded at pressures between 26.6Pa and 798Pa in the temperature of 302–623K range. Results suggest that the adsorption process was the rate controlling step in the FR spectra, and there were two different adsorption processes. Those two processes were attributed to adsorption process of thiophene on SiOH sites (high frequency adsorption) and strong Brönsted acid sites (low frequency adsorption). According to the Yasuda adsorption model and Langmuir rate model, the low frequency sorption did not obey Langmuir model, High frequency adsorption obeyed Langmuir model, which was single layer adsorption. The adsorption sites of low frequency ( Ns (1)) was 0.58mmolg⁻¹ and that of high frequency ( Ns (2)) was 0.92mmolg⁻¹ at 373K. High frequency adsorption was the main adsorption process. High frequency adsorption did not reached saturation adsorption between 302K and 623K, the intensity of the FR spectra reached the maxima atθe(j)=0.5.

Keywords: Thiophene; Frequency response; HZSM-5 sample; Adsorption sites; Adsorption process

Effect of oxygen on the production of abnormally high heats of interaction with hydrogen chemisorbed on gold by A.J. Groszek; E. Lalik (pp. 3192-3195).

▶ Reaction of O₂ with H atoms chemisorbed on Au generates abnormally heat evolutions. ▶ The heats range from 8 to 18 eV per mol of O₂.Abnormally high heats, exceeding 1600kJ/mol (16eV) per molecular oxygen, are generated by interaction of the oxygen with the hydrogen adsorbed on gold surfaces at 125°C. The highest heats were observed during the interactions of fine gold particles supported on titanium oxide, approaching 1700kJ/mol for three consecutive 100nmol pulses of O₂ interacting with the adsorbed hydrogen atoms. The heats rapidly decrease after the hydrogen is consumed. It was also observed that the interactions of the gold particles with pure oxygen in the presence of noble gases, such as argon and helium, produced the heats markedly higher than those observed in the absence of noble gases. The abnormally high heats revealed by this work reach values from 3.5 to 6.1 times higher than the heats of formation of gaseous water from molecular hydrogen and oxygen.

Keywords: Flow microcalorimetry; Gold; Catalyst; Heat of adsorption; Hydrogen; Oxygen; Noble gases

Experimental study of carbon materials behavior under high temperature and VUV radiation: Application to Solar Probe+ heat shield by J. Eck; J.-L. Sans; M. Balat-Pichelin (pp. 3196-3204).

▶ The physico-chemical behavior of carbon materials is experimentally investigated. ▶ Synergistic effect of high temperature and VUV radiation is studied. ▶ VUV radiation induced modification of outgassing and of mass loss rate. ▶ VUV radiation induced alteration of microstructure and morphology.The aim of the Solar Probe Plus (SP+) mission is to understand how the solar corona is heated and how the solar wind is accelerated. To achieve these goals, in situ measurements are necessary and the spacecraft has to approach the Sun as close as 9.5 solar radii. This trajectory induces extreme environmental conditions such as high temperatures and intense Vacuum Ultraviolet radiation (VUV). To protect the measurement and communication instruments, a heat shield constituted of a carbon material is placed on the top of the probe. In this study, the physical and chemical behavior of carbon materials is experimentally investigated under high temperatures (1600–2100K), high vacuum (10⁻⁴Pa) and VUV radiation in conditions near those at perihelion for SP+. Thanks to several in situ and ex situ characterizations, it was found that VUV radiation induced modification of outgassing and of mass loss rate together with alteration of microstructure and morphology.

Keywords: Carbon; Composites; High temperature; Vacuum-UV radiation; Solar Probe

Study of the switching phenomena of TlGaS₂ single crystals by A.A. Al Ghamdi; A.T. Nagat; F.S. Bahabri; R.H. Al Orainy; S.E. Al Garni (pp. 3205-3210).

▶ TlGaS₂ single crystal is grown by locally modified Bridgmen method and its electrical properties were investigated. ▶ It showed a switching effect behavior. ▶ All parameters were extracted. ▶ Our data indicate the possibility of a device application out of this material.Single crystals of TlGaS₂ were prepared by a special modified Bridgman technique and used to investigate the switching phenomena. The particular interest shown in switching studies of p-type TlGaS₂ compound is associated with the possibility of its uses as an effective switching and memory elements in electronic devices. The switching effect observed in such crystal shows a memory character. Using a crystal holder and cryostat we measured the switching phenomenon at different ambient conditions such as temperature, light illumination as well as sample thickness. Pronounced parameters for switching for sample of thickness 0.17cm were determined from the experimental data such as threshold voltage V_th=400V, threshold current I_th=37μA, holding voltage V_h=350V, holding current I_h=42.3×10⁻⁴A, threshold power P_th=1.48×10⁻²W, threshold field E_th=196.429V/cm as well as the ratio between the resistance in the off state R_OFF to the resistance in the conducting state R_ON as 130.253. The factors affecting these parameters have also been investigated.

Keywords: Switching effect; Memory; Crystal growth; TlGaS; ₂

Fabrication of nanoporous manganese by laser cladding and selective electrochemical de-alloying by Yu Gu; Changsheng Dong; Minlin Zhong; Mingxing Ma; Lin Li; Wenjin Liu (pp. 3211-3215).

▶ Nanoporous Mn was fabricated by dealloying of Cu-Mn alloy due to passivation. ▶ The influence of dealloying parameters was systematically investigated. ▶ The roughness factor of nanoporous Mn was enhanced up to 990.Fabrication of nanoporous Cu–Mn alloy coatings was investigated by a two-step process involving high power laser cladding of a homogeneous Cu40Mn60 alloy coatings followed by selectively electrochemical de-alloying. Auger mapping results indicate that nanoporous manganese was obtained by selective electrochemical etching of the less active Cu component owing to the passivation of the more active manganese in potassium nitrate solution. The surface morphology of the porous Mn was a ribbon-like structure, different from interconnected bicontinuous nanopores that are usually obtained by de-alloying. The influence of de-alloying time, electric potential and temperature on the formation of nanoprosity is systematically investigated. Nanopore sizes can be tailored to be less than 100nm. Under optimal etching conditions the nanopore size was below 25nm. The surface area of the nanoporous manganese layer was enhanced by up to 990 times compared with that of a polished sample.

Keywords: Nanoporous manganese; De-alloying; Cu–Mn alloy coating; Laser cladding

Low-temperature ordering and enhanced coercivity of L1₀-FePt thin films with Al underlayer by F.J. Yang; H. Wang; H.B. Wang; B.Y. Wang; X.L. Wang; H.S. Gu; C.P. Yang (pp. 3216-3219).

▶ Al underlayer is inserted between FePt films and SiO₂ substrate. ▶ The annealing temperature and coercivity of FePt films can be lowed and enhanced respectively. ▶ No Al atoms are detected in the interior of FePt films. ▶ The mismatch between Al underlayer and FePt films causes the lower annealing temperature.FePt multilayer films with and without Al underlayer were prepared by magnetron sputtering on SiO₂ substrate and subsequently annealed in vacuum. Experimental results suggest that the existence of Al underlayer can effectively reduce the ordering temperature and increase the coercivity of FePt films. Due to the slight larger lattice constant of Al underlayer than that of FePt films, [Fe (0.66nm)/Pt (0.84nm)]₃₀ films begin to order at 350°C and the coercivity of them reach to 5.7kOe after annealing at 400°C for half an hour.

Keywords: PACS; 68.55. Jk; 61.10. Nz; 68.35. Fx; 64.60. Cn; 68.65. AcMagnetron sputtering; Multilayer FePt films; Al underlayer; Phase transformation

Effect of surface roughness and release layer on anti-adhesion performance of the imprint template by Yugang Duan; Yingjie Li; Yucheng Ding; Dichen Li (pp. 3220-3225).

▶ The appropriate increase of surface roughness could improve hydrophobicity of the template with fluorinated release SAMs. ▶ The demolding force decreased by 56.64% with the treated template. ▶ There was no obvious damage of the treated template surface after 100 times imprint performance.UV imprint lithography has been initiated as an enabling, cost-effective technique to achieve 100nm resolution patterning in recent years. However, the adhesion between resist and imprint template is one of the critical problems for the industrial application of imprint lithography. In this paper, two kinds of measures, including increase of surface roughness of template and application of a fluorinated release agent as self-assembled monolayers (SAMs) to the template surface, were taken to overcome the adhesion between resist and template. The test results of contact angle showed that the appropriate increase of surface roughness could improve hydrophilicity of template surface greatly, and improved the hydrophobicity of template surface when it was combined with self-assembled monolayers. The XPS, DRIR spectra indicated that the fluorinated release layers were successfully prepared on the surface of template using the process in the paper. The surface free energy of the template was 16.6mN/m, and less than that of PTFE (18mN/m). The imprint experiment results also showed that the anti-adhesion performance of treated template was improved greatly during detaching procedure, and the demolding force decreased by 56.64% in comparison with that of untreated template.

Keywords: Imprint template; Anti-adhesion; Roughness; Self-assembled monolayers

Adsorption and desorption of dibenzothiophene on Ag-titania studied by the complementary temperature-programmed XPS and ESR by Alexander Samokhvalov; Evert C. Duin; Sachin Nair; Bruce J. Tatarchuk (pp. 3226-3232).

▶ DBT chemisorbs from model fuel on TiO₂ and Ag/TiO₂ via O surface groups. ▶ DBT binds stronger to O sites of Ag/TiO₂ that to these of TiO₂. ▶ Adsorption complex “Ag/Titania+DBT” is stable under XPS conditions. ▶ XPS spectrum of pure DBT is reported for the first time. ▶ Adsorption complex undergoes desorption ∼175–325°C and degradation ∼325–525°C.Adsorption, desorption and structure of the surface chemical compounds formed upon interaction of dibenzothiophene (DBT) in solution of n-octane with the sulfur-selective Ag/Titania sorbent for the ultradeep desulfurization of liquid fuels was characterized by the temperature-programmed X-ray photoemission spectroscopy (XPS) and Electron Spin Resonance. Adsorption of DBT proceeds via chemisorption via the oxygen-containing surface groups. Desorption of DBT and thermal regeneration of the “spent” Ag/Titania were studied by the complementary temperature-programmed XPS and ESR from 25°C to 525°C, in the high vacuum vs. air. The XPS spectrum of the pure DBT is reported for the first time.

Keywords: Dibenzothiophene; Fuel desulfurization sorbent; In-situ; temperature-programmed XPS; ESR; Ag/Titania

Self-assembled tetramethylbenzidine conductive nanofibers synchronized with gold nanoparticle formation by Nguyen Dang Luong; Joonsuk Oh; Youngkwan Lee; Jaehyun Huh; Jong Jin Park; Jong Min Kim; Jae-Do Nam (pp. 3233-3235).

▶ In this study, for the first time, we report an in-situ synthesis of tetramethylbenzidine/Au (TMB/Au) nanocomposite fibers. ▶ Interestingly, these fibers grow uniformly decorated with a large amount of Au nanoparticles via chemical redox reaction of TMB and HAuCl₄ in ethanol media. ▶ Remarkably, TMB/Au nanocomposite fibers are conductive and its conductivity is 2.1×10⁻³scm⁻¹. ▶ The nanocomposite material developed herein can find various applications such as optoelectronic devices and sensors.In this study, for the first time, electrically-conductive tetramethylbenzidine (TMB) nanofibers were synthesized and covered with gold nanoparticles via the in situ redox reaction of TMB and HAuCl₄ in ethanol media. The gold nanoparticles were uniformly bound to the fiber surface through the coordination of the amine atoms in TMB molecules with gold nanoparticles. The conductivity of the composite fibrous membrane was found to be 2.1×10⁻³Scm⁻¹. The developed method described herein is simple and effective for the production of novel electrically-conductive TMB/Au nanofibers. We believed that the composite fibrous materials could be used in various fields such as optoelectronic or sensor applications.

Keywords: Fiber technology; Gold nanoparticles; Nanocomposites; Nanomaterials

Pseudo-template synthesis of gold nanoparticles based on polyhydrosilanes by Liviu Sacarescu; Mihaela Simionescu; Gabriela Sacarescu (pp. 3236-3242).

▶ Microwaves irradiation of polyhydrosilanes activates latent reactive centers. ▶ Photo scission and chemo-restructuring of the polysilane backbone generate radicals. ▶ The generated radicals function as reducing agents of the metal salt. ▶ Nucleation within the pseudo-template system leads to polymer–gold nanoparticles.Highly stable colloidal gold nanoparticles are obtained in a pseudo-template system using a specific polyhydrosilane copolymeric structure. This process takes place in situ by microwaves activation of the polymer solution in a non-polar solvent followed by stirring with solid HAuCl₄ in natural light. The experimental procedure is very simple and the resulted colloidal gold solution is indefinitely stable. The specific surface plasmon resonance absorption band of the gold nanoparticles is strongly red shifted and is strictly related to their size. AFM correlated with DLS analysis showed flattened round shaped colloidal polymer–gold nanoparticles with large diameters. SEM-EDX combined analysis reveals that the polysilane–gold nanoparticles show a natural tendency to auto-assemble in close packed structures which form large areas over the polymer film surface.

Keywords: Gold nanoparticle; Synthesis; Template; Nanocomposite; Polysilanes

Insight into STM image contrast of n-tetradecane and n-hexadecane molecules on highly oriented pyrolytic graphite by Miao Zhao; Peng Jiang; Ke Deng; Ai-Fang Yu; Yan-Zhong Hao; Si-Shen Xie; Jie-Lin Sun (pp. 3243-3247).

▶ Scanning tunneling microscope (STM) images n-tetradecane ( n-C₁₄H₃₀) and n-hexadecane ( n-C₁₆H₃₄) self-assembled monolayers on HOPG. ▶ The molecular axes of n-C₁₄H₃₀ molecules tilt by 60° with respect to inter-lamellar trough lines on HOPG. ▶ The carbon backbones of n-C₁₄H₃₀ molecule chains are perpendicular to the HOPG basal plane in an all-trans conformation. ▶ The molecular axes of n-C₁₆H₃₄ molecules are perpendicular to lamellar borders (90°) on HOPG. ▶ Topographic effects determine STM image contrast of the methylene regions of the alkane chains on HOPG.Two-dimensional ordered patterns of n-tetradecane ( n-C₁₄H₃₀) and n-hexadecane ( n-C₁₆H₃₄) molecules at liquid/graphite interface have been directly imaged using scanning tunneling microscope (STM) under ambient conditions. STM images reveal that the two different kinds of molecules self-organize into ordered lamellar structures in which alkane chains of the molecules extend along one of three equivalent lattice axes of highly oriented pyrolytic graphite (HOPG) basal plane. For n-C₁₄H₃₀ molecules, the molecular axes are observed to tilt by 60° with respect to inter-lamellar trough lines and the carbon backbones of the alkane chains are perpendicular to the HOPG basal plane in an all-trans conformation. However, for n-C₁₆H₃₄ molecules, the molecular axes are perpendicular to lamellar borders (90°) and the planes of the all-trans carbon skeletons are parallel to the graphite basal plane. The results clearly indicate that outmost hydrogen atoms of the alkane chains dominate atom-scaled features of the STM images. That is, in the case of long-chain alkane molecules, topographic effects dominantly determine STM image contrast of the methylene regions of the alkane chains that are adsorbed on HOPG.

Keywords: Scanning tunneling microscope; Self-assembly; Alkane

Growth mechanisms for wire-like epitaxial gold silicide islands on Si(110) surfaces by R. Batabyal; S. Patra; A. Roy; B.N. Dev (pp. 3248-3252).

▶ We compare mechanisms for the growth of self-organized epitaxial nanowires. ▶ Shape-transition and anisotropic diffusion mechanisms are compared. ▶ Growth of gold silicide nanowires on Si(110) surfaces has been investigated. ▶ The nanowires grow predominantly via anisotropic diffusion.Epitaxial islands grown on various substrates are usually strained because of differences in lattice constants of the materials of the island and the substrate. Shape transition in the growth of strained islands has been proposed as a mechanism for strain relief and a way to form self-organized quantum wires. Shape transition usually leads to an elongated island growth. However, an elongated island growth may also be due to an anisotropic diffusion of material, the anisotropy being imposed by the symmetry of the substrate surface. In the present example, growth of gold silicide wire-like nanostructures on a Si(110) surface has been investigated by photoemission electron microscopy (PEEM). Growth of elongated unidirectional gold silicide islands, with an aspect ratio as large as 12:1, has been observed by PEEM following gold deposition on the Si substrate and subsequent annealing at the Au–Si eutectic temperature. Distribution of the width and the length of the gold silicide islands as a function of island area shows a feature similar to that for the shape transition. However, detailed investigations reveal that the elongated growth of gold silicide islands is rather mainly due to anisotropic diffusion of gold due to the twofold symmetry of the (110) surface of the Si substrate.

Keywords: PACS; 81.07.Gf; 81.16.Rf; 68.37.Xy; 66.30.PaSelf-organized growth of epitaxial nanowires; Photoemission electron microscopy (PEEM); Anisotropic diffusion

Hydrothermal synthesis and electrochemical characterization of VO₂ (B) with controlled crystal structures by Wentao Jiang; Juan Ni; Ke Yu; Ziqiang Zhu (pp. 3253-3258).

▶ The ammonium metavanadate and oxalic acid as the experimental material has never been reported to the best of our knowledge. ▶ We successfully fabricated the novel urchin-like VO2 (B). ▶ We compared and analysed the electrochemical behaviors of three different morphologies of the VO2 (B).Three different VO₂ (B) nanostructures, including urchin-like VO₂ (B), VO₂ (B) honeycombs and VO₂ (B) nanorods have been successfully fabricated through hydrothermal process by adjusting the concentrations of the oxalic acid. The microstructure and morphology of the VO₂ nanostructures were evaluated by using X-ray diffraction and scanning and transmission electron microscopies. Electrochemical properties measurements of urchin-like VO₂ (B) and VO₂ (B) honeycombs showed excellent cycling performance, especially the urchin-like VO₂ (B) exhibited higher discharge capacity and better capacity retention.

Keywords: PACS; 81.07.Bc; 82.45.Yz; 82.47.AaVO; ₂; (B) nanostructures; Hydrothermal synthesis; Electrochemical property

An improved planar-gate triode with CNTs field emitters by electrophoretic deposition by Y.A. Zhang; C.X. Wu; J.Y. Lin; Z.X. Lin; T.L. Guo (pp. 3259-3264).

▶ We have developed an electrophoretic process to selectively deposit CNTs emitters onto the surface of cathode electrodes and an improved planar-gate triode with CNTs field emitters has been successfully fabricated by conventional photolithography, screen printing and electrophoretic deposition and investigated its field emission characteristics. ▶ The experiment result showed that the CNTs emitters were selectively deposited cathode electrodes and each cathode electrodes had the uniform packing density. ▶ The field emission characteristics indicated that turn-on voltage of an improved planar-gate triode at current density of 1μA/cm² was around 55V. ▶ When gate voltage was higher than turn-on voltage, the anode and gate current continually increased under the role of gate voltage. ▶ However, the increase ratio of gate current seemed to be higher than that of anode current as gate voltage was higher than 90V. ▶ Although the emission efficiency was modified from 94.8% to 54.9%, the emission image became brighter and the luminous image with dot matrix on the anode plate obviously increased with the increases of gate voltage from 0V to 100V with anode bias of 4000V and the anode–cathode spacing was about 2000μm. ▶ Moreover, the emission current fluctuation was smaller than 5% for 11h, which indicated that the fabricated device had a good field emission performance and long lifetime. ▶ In a word, this improved planar-gate triode with CNTs field emitters easily realizes the scan between gate and cathode electrodes in the drive circuit and presents the field emission image with dot matrix, which may lead to practical applications for dynamic back light unit and field emission displays.An improved planar-gate triode with carbon nanotubes (CNTs) field emitters has been successfully fabricated by conventional photolithography, screen printing and electrophoretic deposition (EPD). In this structure, cathode electrodes and ITO arrays linked with gate electrodes were interdigitated and paralleled on the same plane although the gate electrodes and cathode electrodes were isolated by dielectric layer, a so-called improved planar-gate triode structure. An electrophoretic process was developed to selectively deposit CNTs field emitters onto cathode electrodes in the CNTs suspension by an applied voltage between the gate electrodes and cathode electrodes. The optical microscopy and FESEM image showed that the CNTs emitters with the uniform packing density were selectively defined onto the cathode electrodes. In addition, field emission characteristics of an improved planar-gate triode with CNTs field emitters were investigated. The experiment results indicated that the turn-on voltage of this triode structure at current density of 1μA/cm² was approximately 55V. The anode current and gate current came to 396μA and 325μA, at gate voltage and anode voltage of 100V and 4000V, respectively and at the anode–cathode spacing of 2000μm. The emission image became brighter and the luminous image with dot matrix on the anode plate obviously increased with the increase of the gate voltage. Moreover, the emission current fluctuation was smaller than 5% for 11h, which indicated that the improved planar-gate triode has a good field emission performance and long lifetime.

Keywords: Carbon nanotubes; Planar-gate triode; Field emission; Electrophoretic deposition

Surface tension and density of liquid Sn–Ag alloys by Przemysław Fima (pp. 3265-3268).

▶ Surface tension and density show linear dependence on temperature. ▶ Molar volume shows close to a linear change with composition. ▶ Measured data agree relatively well with results of Butler model calculations. ▶ Present results are in agreement with the data of earlier studies.The surface tension and density measurements for Sn–Ag alloys were carried out with the sessile drop method. Seven different compositions were investigated in the range from 0.011 to 0.5 mole fraction of Ag, in a broad range of temperature. With increasing concentrations of Ag, both density and the surface tension are increased. With increasing temperature the density decreases for all of the alloys. A decrease of the surface tension is observed for most of the composition except for the alloy of 0.5 mole fractions of Ag. The obtained results are compared with existing literature data and Butler model calculations and relatively good agreement is observed.

Keywords: Key words; Sn–Ag alloys; Surface tension; Density; Sessile drop method

Characterization and corrosion study of NiTi laser surface alloyed with Nb or Co by K.W. Ng; H.C. Man; T.M. Yue (pp. 3269-3274).

▶ In the present study, NiTi was surface alloyed with Nb or Co by laser processing. ▶ The amount of surface elemental Ni was reduced to 10% and 35% for the Nb-alloyed and Co-alloyed layer, respectively. ▶ The corrosion resistance in Hanks’ solution was increased as evidenced by a reduced passive current density and a higher pitting potential for both the Nb- and Co-alloyed specimens. ▶ The microhardness of the alloyed layers was around 700–800Hv, which was about four times that of the untreated NiTi specimens.The interest in NiTi alloys for medical applications has been steadily growing in recent years because of its biocompatibility, superelasticity and shape memory characteristics. However, the high Ni content in NiTi alloys is still a concern for its long-term applications in the human body. The release of Ni ion into the human body might cause serious problems, as Ni is capable of eliciting toxic and allergic responses. In view of this, surface modification to reduce the surface content of Ni and to improve the corrosion resistance, both of which would reduce Ni release, is an important step in the development of NiTi implants. In the present study, NiTi was surface alloyed with Nb or Co by laser processing. The fine dendritic structure characteristic of laser processing has been described in terms of rapid solidification. The amount of surface elemental Ni was reduced to 10% and 35% for the Nb-alloyed and Co-alloyed layer, respectively. The corrosion resistance in Hanks’ solution (a simulated body fluid) was increased as evidenced by a reduced passive current density and a higher pitting potential for both the Nb- and Co-alloyed specimens. The composition and hardness profiles along the depth of the modified layer were correlated with the distribution of the dendrites. The microhardness of the alloyed layers was around 700–800Hv, which was about four times that of the untreated NiTi specimens.

Keywords: Laser surface alloying; NiTi; Niobium; Coblat; Corrosion resistance

In situ ellipsometric study of electrodeposition of manganese films on copper by Wenpo Li; Shengtao Zhang (pp. 3275-3280).

▶ Electrodeposition of manganese film accompanied with hydrogen evolution was investigated by in situ spectroscopic ellipsometry (SE) with cyclic voltammetry (CV). ▶ The hydrogen evolution has no influence on the SE measurement. ▶ The growth kinetics of manganese electrodeposition was proposed according to the SE measurements.Electrodeposition of manganese film on copper substrate in a chloride-based solution was investigated by cyclic voltammetry (CV) in combination with in situ spectroscopic ellipsometry (SE). The SE results at different polarization potentials show that the hydrogen evolution has no influence on the SE measurement. The CV results, confirmed by SE data, indicate the starting reduction and oxidation potentials of manganese. The potential for electrodeposition of manganese film with the maximum thickness was determined based on the SE measurements. The SE results show that the manganese film is relatively loose, which is consistent with the observation by scanning electron microscopy (SEM). The growth kinetics of manganese electrodeposition was proposed according to the SE measurements.

Keywords: Manganese; Electrodeposition; Cyclic voltammetry; In situ spectroscopic ellipsometry

Laser microstructuring for fabricating superhydrophobic polymeric surfaces by M.R. Cardoso; V. Tribuzi; D.T. Balogh; L. Misoguti; C.R. Mendonça (pp. 3281-3284).

Display Omitted▶ Ultrashort laser pulses were used to microstructure a polymeric surface. ▶ Superhydrophobic surfaces were achieved with square-shaped pillars morphology. ▶The surface structuring method allows controlling the surface wetting properties.In this paper we show the fabrication of hydrophobic polymeric surfaces through laser microstructuring. By using 70-ps pulses from a Q-switched and mode-locked Nd:YAG laser at 532nm, we were able to produce grooves with different width and separation, resulting in square-shaped pillar patterns. We investigate the dependence of the morphology on the surface static contact angle for water, showing that it is in agreement with the Cassie–Baxter model. We demonstrate the fabrication of a superhydrophobic polymeric surface, presenting a water contact angle of 157°. The surface structuring method presented here seems to be an interesting option to control the wetting properties of polymeric surfaces.

Keywords: Laser micromachining; Polymers; Superhydrophobic surfaces

Comparison of ZnO thin films grown on a polycrystalline 3C–SiC buffer layer by RF magnetron sputtering and a sol–gel method by Duy-Thach Phan; Gwiy-Sang Chung (pp. 3285-3290).

▶ ZnO thin films grown on a polycrystalline 3C–SiC. ▶ Comparison of sputtered ZnO film and sol–gel method. ▶ Reduced residual stress in ZnO film. ▶ Improved optical properties ZnO film.Zinc oxide (ZnO) thin films were deposited on a polycrystalline (poly) 3C–SiC buffer layer using RF magnetron sputtering and a sol–gel method. The post-deposition annealing was performed on ZnO thin films prepared using both methods. The formation of ZnO piezoelectric thin films with less residual stress was due to a close lattice mismatch of the ZnO and SiC layers as obtained by the sputtering method. Nanocrystalline, porous ZnO film prepared using the sol–gel method showed strong ultraviolet UV emission at a wavelength of 380nm. The 3C–SiC buffer layer improved the optical and piezoelectric properties of the ZnO film produced by the two deposition methods. Moreover, the different structures of the ZnO films on the 3C–SiC intermediate layer caused by the different deposition techniques were also considered and discussed.

Keywords: ZnO; RF sputtering; Sol–gel; 3C–SiC buffer layer

The effect of substrate surface roughness on ZnO nanostructures growth by Maryam Roozbehi; Parvaneh Sangpour; Ali Khademi; Alireza Z. Moshfegh (pp. 3291-3297).

▶ Our work has demonstrated that the surface roughness of substrate is an important parameter in final formation of the deposited ZnO nanostructure. ▶ The role of the different substrates and two types of the carrier gas flow on the growth of ZnO nanowire were investigated. ▶ Si substrate was found to be the best substrate for the growth of ZnO nanowires with small and uniform diameter and regular shape. ▶ The field emission property of the ZnO nanowires grown on Si substrate without epi-layer was studied under UHV conditions at room temperature for different cathode–anode separation distances. The obtained experimental data are well agreed with the Fowler–Nordheim theory.The ZnO nanowires have been synthesized using vapor–liquid–solid (VLS) process on Au catalyst thin film deposited on different substrates including Si(100), epi-Si(100), quartz and alumina. The influence of surface roughness of different substrates and two different environments (Ar+H₂ and N₂) on formation of ZnO nanostructures was investigated. According to AFM observations, the degree of surface roughness of the different substrates is an important factor to form Au islands for growing ZnO nanostructures (nanowires and nanobelts) with different diameters and lengths. Si substrate (without epi-taxy layer) was found that is the best substrate among Si (with epi-taxy layer), alumina and quartz, for the growth of ZnO nanowires with the uniformly small diameter. Scanning electron microscopy (SEM) reveals that different nanostructures including nanobelts, nanowires and microplates have been synthesized depending on types of substrates and gas flow. Observation by transmission electron microscopy (TEM) reveals that the nanostructures are grown by VLS mechanism. The field emission properties of ZnO nanowires grown on the Si(100) substrate, in various vacuum gaps, were characterized in a UHV chamber at room temperature. Field emission (FE) characterization shows that the turn-on field and the field enhancement factor ( β) decrease and increases, respectively, when the vacuum gap ( d) increase from 100 to 300μm. The turn-on emission field and the enhancement factor of ZnO nanowires are found 10V/μm and 1183 at the vacuum gap of 300μm.

Keywords: ZnO nanowires; Au catalyst; VLS; Field emission

Luminescence characterization and electron beam induced chemical changes on the surface of ZnAl₂O₄:Mn nanocrystalline phosphor by Shreyas S. Pitale; Vinay Kumar; I.M. Nagpure; O.M. Ntwaeaborwa; H.C. Swart (pp. 3298-3306).

▶ Stable green cathodoluminescence (CL) obtained under low voltage electron beam excitation. ▶ Auger and XPS probed chemical changes on the surface of the ZnAl₂O₄:Mn²⁺. ▶ A thermodynamically stable Al₂O₃ layer stabilises the CL.Luminescence characteristics and surface chemical changes of nanocrystalline Mn²⁺ doped ZnAl₂O₄ powder phosphors are presented. Stable green cathodoluminescence (CL) or photoluminescence (PL) with a maximum at ∼512nm was observed when the powders were irradiated with a beam of high energy electrons or a monochromatic xenon lamp at room temperature. This green emission can be attributed to the⁴T₁→⁶A₁ transitions of the Mn²⁺ ion. Deconvoluted CL spectra resulted in two additional emission peaks at 539 and 573nm that may be attributed to vibronic sideband and Mn⁴⁺ emission, respectively. The luminescence decay of the Mn²⁺ 512nm emission under 457nm excitation is single exponential with a lifetime of 5.20±0.11ms. Chemical changes on the surface of the ZnAl₂O₄:Mn²⁺ phosphor during prolonged electron beam exposure were monitored using Auger electron spectroscopy. The X-ray photoelectron spectroscopy (XPS) was used to determine the chemical composition of the possible compounds formed on the surface as a result of the prolonged electron beam exposure. The XPS data suggest that the thermodynamically stable Al₂O₃ layer was formed on the surface and is possibly contributing to the CL stability of ZnAl₂O₄:Mn phosphor.

Keywords: Cathodoluminescence; Auger electron spectroscopy; X-ray photoelectron spectroscopy

Morphology and transmittance of porous alumina on glass substrate by Guo Peitao; Xia Zhilin; Xue Yiyu; Huang Caihua; Zhao Lixin (pp. 3307-3312).

▶ Porous anodic alumina (PAA) with ordered pore structure is chose for the study of mechanism of laser-induced damage of porous optical film. ▶ The pores on the alumina are the highly vulnerable to damage under the radiation of laser. ▶ Grow PAA films on glass, which opens up the possibility of a host of application that involve optics and biologically relevant microscopic work.The porous optical film has higher threshold of laser-induced damage than densified films, for the study of mechanism of laser-induced damage of porous optical film with ordered pore structure. Porous anodic alumina (PAA) film with high transmittance on glass substrate has been prepared. Aluminum film was deposited on glass substrate by means of resistance and electron beam heat (EBH) evaporation. Porous alumina was prepared in oxalic acid solution under different anodizing conditions. At normal incidence, the optical transmittance spectrum over 300–1000nm spectra region was obtained by spectrophotometer. SEM was introduced to analysis the morphology of the porous alumina film. The pore aperture increased with the increase of anodizing voltage, which resulted in a rapid decrease of the pore concentration and the optical thickness of porous alumina film. Damage morphology of porous alumina film is found to be typically defects initiated, and the defect is the pore presented on the film.

Keywords: Porous alumina; Glass substrate; Optical property; Laser-induced damage; Morphology

Electrical and optical properties of thermally-evaporated thin films from A₂[TiO(C₂O₄)₂] (A=K, PPh₄) and 1,8-dihydroxyanthraquinone by E. Carbia-Ruelas; M.E. Sánchez-Vergara; V. García-Montalvo; O.G. Morales-Saavedra; J.R. Álvarez-Bada (pp. 3313-3319).

▶ Synthesis of molecular materials formed from A₂[TiO(C₂O₄)₂] (A=K, PPh4) and 1,8 dihydroxyanthraquinone. ▶ Thin films show electrical conductivities of the order of 10⁻⁵Scm⁻¹. ▶ Optical studies showed that the optical band gaps of the thin films were around 1.9−2.3eV. ▶ The measurement of cubic-only, non-degenerated χ (3) (−3ω; ω, ω, ω) NLO coefficients in all the studied samples, instead of quadratic- χ (2) ones, pointed out to predominantly amorphous structured-molecular arrangements.In this work, the synthesis of molecular materials formed from A₂[TiO(C₂O₄)₂] (A=K, PPh4) and 1,8 dihydroxyanthraquinone is reported. The synthesized materials were characterized by atomic force microscopy (AFM), infrared (IR) and ultraviolet-visible (UV–vis) spectroscopy. IR spectroscopy showed that the molecular-material thin-films, deposited by vacuum thermal evaporation, exhibit the same intra-molecular vibration modes as the starting powders, which suggests that the thermal evaporation process does not alter the initial chemical structures. Electrical transport properties were studied by dc conductivity measurements. The electrical activation energies of the complexes, which were in the range of 0.003–1.16eV, were calculated from Arrhenius plots. Optical absorption studies in the wavelength range of 190–1090nm at room temperature showed that the optical band gaps of the thin films were around 1.9–2.3eV for direct transitions Eg_d. The cubic NLO effects were substantially enhanced for materials synthesized from K₂[TiO(C₂O₄)₂], where χ⁽³⁾ (−3 ω; ω, ω, ω) values in the promising range of 10⁻¹²esu have been evaluated.

Keywords: Thin films; Optical properties; Electrical properties; NLO-effect

Effect of substrate temperature on gold-catalyzed silicon nanostructures growth by hot-wire chemical vapor deposition (HWCVD) by Su Kong Chong; Boon Tong Goh; Zarina Aspanut; Muhamad Rasat Muhamad; Chang Fu Dee; Saadah Abdul Rahman (pp. 3320-3324).

▶ Au catalyzed silicon nanostructures prepared by HWCVD at substrate temperature of equal and less than 400°C. ▶ Au induced crystallization in silicon nanostructures. ▶ The as-grown silicon nanostructures consist of high density of nanocrystallites embedded within amorphous matrix.The effect of substrate temperature on the structural property of the silicon nanostructures deposited on gold-coated crystal silicon substrate by hot-wire chemical vapor deposition (HWCVD) was studied. The uniformity and size of the as-grown silicon nanostructures is highly influenced by the substrate temperature. XRD, Raman and HRTEM measurements show the silicon nanostructures consist of small crystallites embedded within amorphous matrix. The crystallite size of the as-grown silicon nanostructures decreases with increases in substrate temperature. FTIR shows that these silicon nanostructures are highly disordered for sample prepared at substrate temperature above 250°C. The correlation of crystallinity and structure disorder of the silicon nanostructures growth at different substrate temperature was discussed.

Keywords: Silicon nanostructures; HWCVD; Crystallinity; HRTEM; Microstructure parameter

Effect of uniaxial strain on adatom diffusion across {111}-faceted step by Jianyu Yang; Wangyu Hu; Jianfeng Tang (pp. 3325-3330).

▶ Diffusion of Pt adatom across the strained {111}-faceted step is studied. ▶ For adatom on the flat (111) surface, the anisotropic diffusion behavior is found as the uniaxial strain is imposed. ▶ For the strained {111}-faceted step, the maximum energy barrier for adatom crossing step edge remains approximately constant as the strain varied from −1.0% to 1.0%. ▶ The energy barrier for adatom diffusion along the step edge increases with increasing tensile strain.Diffusion of Pt adatom across the strained {111}-faceted step is studied by embedded atom method along with nudged elastic band method. For adatom on the flat (111) surface, the anisotropic diffusion behavior is found as the uniaxial strain is imposed. For the strained {111}-faceted step, our results show that the maximum energy barrier for adatom crossing step edge remains approximately constant as the strain varied from −1.0% to 1.0%, and there is a rise as the larger uniaxial strain is applied. The calculated energy barrier for adatom diffusion along the step edge increases with increasing tensile strain, and the slope of the straight line is small.

Keywords: PACS; 68.35.Gy; 68.47.De; 68.43.JkSurface strain; Metallic surfaces; Surface diffusion

Oscillations of light absorption in 2D macroporous silicon structures with surface nanocoatings by L. Karachevtseva; S. Kuchmii; O. Lytvynenko; F. Sizov; O. Stronska; A. Stroyuk (pp. 3331-3335).

▶ We observed the well-separated light absorption oscillations in the spectral ranges of the surface bonds of 2D macroporous silicon structures with microporous silicon layers and CdTe, ZnO surface nanocrystals. ▶ The model of the resonant electron scattering on impurity states in electric field of heterojunction “silicon-nanocoating” on macropore surface and realization of Wannier–Stark effect were considered. ▶ The Wannier–Stark ladders are not broken by impurities due to the longer scattering lifetime as compared with the electron oscillation period.We investigated the near-IR light absorption oscillations in 2D macroporous silicon structures with microporous silicon layers and CdTe, ZnO surface nanocrystals. The electro-optical effect was taken into account within the strong electric field approximation. Well-separated oscillations were observed in the spectral ranges of the surface bonds of macroporous silicon structures with surface nanocrystals. The model of the resonant electron scattering on impurity states in electric field of heterojunction “silicon-nanocoating” on macropore surface as well as realization of Wannier–Stark effect on the randomly distributed surface bonds were considered. The Wannier–Stark ladders are not broken by impurities because of the longer scattering lifetime as compared with the period of electron oscillations in an external electric field, in all spectral regions considered for macroporous silicon structures with CdTe and ZnO surface nanocrystals.

Keywords: Macroporous silicon; Nanocoatings; Wannier–Stark effect

Regulation of the elastic modulus of polyurethane microarrays and its influence on gecko-inspired dry adhesion by Ming Li; Aiwu Zhao; Rui Jiang; Dapeng Wang; Da Li; Hongyan Guo; Wenyu Tao; Zibao Gan; Maofeng Zhang (pp. 3336-3340).

▶ Segmented polyurethane was utilized to fabricate microarrays. ▶ The elastic modulus and adhesion of microarrays were investigated by Triboindenter. ▶ Decrease of elastic modulus can enhance the adhesion.We studied the influence of the elastic modulus on the gecko-inspired dry adhesion by regulating the elastic modulus of bulk polyurethane combined with changing the size of microarrays. Segmented polyurethane (PU) was utilized to fabricate micro arrays by the porous polydimethyl siloxane (PDMS) membrane molding method. The properties of the micro arrays, such as the elastic modulus and adhesion, were investigated by Triboindenter. The study demonstrates that bulk surfaces show the highest elastic modulus, with similar values at around 175MPa and decreasing the arrays radius causes a significant decrease in E, down to 0.62MPa. The corresponding adhesion experiments show that decrease of the elastic modulus can enhance the adhesion which is consistent with the recent theoretical models.

Keywords: Gecko-inspired; Dry adhesion; Polyurethane; Microarrays; Triboindenter

Structures of CoAl(111) surface: A first principles study by Zhongjie Xu; Zhenghong Dai; Jun Ni (pp. 3341-3345).

▶ Al segregation tendency plays dominant role on the CoAl(111) surface. ▶ There are three stable states in the CoAl(111) surface phase diagram. ▶ The barriers from the initial surface structure to the stable structure are large.The structures of the CoAl(111) surface are studied by first principles calculations. Our calculations show that the surface layer is always occupied by pure Al for all concentrations studied here, which indicates the dominant role of the Al segregation tendency. This is different from the CoAl(001) surface, where a number of Co anti-sites are found on the top most layer. The calculated surface phase diagram of ground states shows that there are three stable structures. The diffusion barriers of the metastable structure evolving to the stable structure are also calculated. The high diffusion barrier can explain the appearance of metastable structures at low temperature in experiment.

Keywords: Metallic surfaces; Surface energies; Segregation; Kinetics

ZnTe/GaAs(211)B heterojunction valence band discontinuity measured by X-ray photoelectron spectroscopy by X.J. Wang; S.Tari; R. Sporken; S. Sivananthan (pp. 3346-3349).

▶ Valence band offset of GaAs/ZnTe is found to be 0.25±0.1eV. ▶ Alignment is type I. ▶ No indication of intermixing was observed at the interface. ▶ Strain does not seem to affect the value found for VBO.Thin ZnTe layers were grown by molecular beam epitaxy on single crystal GaAs(211)B substrates. Reflection high energy electron diffraction monitored the deoxidation of substrate and entire growth process. Valence band offset was calculated with X-ray photoelectron spectroscopy. Also interface formation of the ZnTe/GaAs was studied. Analysis shows that interface is abrupt and calculated valance band offset is 0.25±0.1eV and indicates type I alignment. The experimental result agrees well with the theoretical predictions involving interface dipole effect as well as electron affinity rule.

Keywords: Valence band offset; XPS; Strain; Intermixing; Epitaxy

A simple approach for immobilization of gold nanoparticles on graphene oxide sheets by covalent bonding by Tuan Anh Pham; Byung Choon Choi; Kwon Taek Lim; Yeon Tae Jeong (pp. 3350-3357).

▶ The surface functionalization of gold nanoparticles obtanied using 4-aminothiophenol through Au-S chemistry. ▶ The functionalized gold nanoparticles were well immobilized on the graphene oxide surface via amide bonding. ▶ The resulting novel hybrid was investigated in detail using various techniques.Amino—functionalized gold nanoparticles with a diameter of around 5nm were immobilized onto the surface of graphene oxide sheets (GOS) by covalent bonding through a simple amidation reaction. Pristine graphite was firstly oxidized and exfoliated to obtain GOS, which further were acylated with thionyl chloride to give acyl chloride bound GOS. Gold nanoparticles (AuNPs) were functionalized using 4-aminothiophenol in a single-phase system to introduce amino groups on their surface through the well-developed Au–S chemistry. Subsequently, amino groups of AuNPs were reacted with acyl chloride groups of GOS to form a novel hybrid material containing GOS and AuNPs. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy were used to study the changes in surface functionalities and demonstrate the successful immobilization of AuNPs on GOS surface. High resolution transmission electron microscopy (HR-TEM), field emission scanning electronic microscopy (FE-SEM), and atomic force microscopy (AFM) were employed to investigate the morphologies of prepared AuNPs and their distribution onto the GOS surface. Thermogravimetric analysis (TGA) was used to characterize the thermal stability of the samples on heating.

Keywords: Gold nanoparticles; Graphene oxide; Functionalization; Covalent immobilization; Hybrid material

Valence control of cobalt oxide thin films by annealing atmosphere by Shijing Wang; Boping Zhang; Cuihua Zhao; Songjie Li; Meixia Zhang; Liping Yan (pp. 3358-3362).

▶ Co₃O₄ and CoO thin films were fabricated via a chemical solution approach. ▶ The phase structure was tailored by controlling the annealing atmosphere. ▶ The valence control of Co₃O₄ and CoO contributes to the optical absorption property.The cobalt oxide (CoO and Co₃O₄) thin films were successfully prepared using a spin-coating technique by a chemical solution method with CH₃OCH₂CH₂OH and Co(NO₃)₂·6H₂O as starting materials. The grayish cobalt oxide films had uniform crystalline grains with less than 50nm in diameter. The phase structure is able to tailor by controlling the annealing atmosphere and temperature, in which Co₃O₄ thin film was obtained by annealing in air at 300–600, and N₂ at 300, and transferred to CoO thin film by raising annealing temperature in N₂. The fitted X-ray photoelectron spectroscopy (XPS) spectra of the Co2p electrons are distinguishable from different valence states of cobalt oxide especially for their satellite structure. The valence control of cobalt oxide thin films by annealing atmosphere contributes to the tailored optical absorption property.

Keywords: Cobalt oxide; Annealing atmosphere; Thin film; XPS; Optical property

Analysis the complex interaction among flexible nanoparticles and materials surface in the mechanical polishing process by Xuesong Han; Yong X. Gan (pp. 3363-3373).

▶ The increasing demand for functional enhancement, ultra-lapping or polishing has been recognized as a critical technology for the functional materials of the precision machinery components, optical components, and electronic components. Further study on physical aspects of nanometer manufacturing technology is crucial for obtaining planarization surface whose roughness at the nanometer level. ▶ The final surface integrity acquired using mechanical polishing (MP) technique is mainly depended on the microdynamic behavior of nanoparticles. The complex multibody interaction among nanoparticles and materials surface is different from interaction in the macroscopic scale which makes the traditional classical materials machining theory cannot accurately uncover the mystery of the surface generation in the MP. As the size of the particles decreases and approaches molecular dimensions, their atomic nature becomes increasingly important. A straightforward interpretation of experimental results is often not possible due to the complexity of the dynamics. The use of molecular dynamics (MD) simulation techniques has therefore become a very important tool in this field. ▶ The polishing is a many body nanometer machining technology, and there exists complex interaction among particles as well as the interaction among particles and substrate materials. As this interaction falls into the nanometer regime, it is not downsizing but some new discipline and mechanism dominate the MP technology. Traditional continuum mechanics or experimental method cannot give reasonable explanation about this microscopic dynamic process. It is seems that only combining all kinds of particle actions and various characteristic polishing conditions can the physical essence of MP be discovered. Large-scale classical molecular dynamic (MD) simulation of interaction among nanoparticles and solid surface has been carried out to investigate the physical essence of surface planarization and drew some meaningful conclusions. ▶ The particles with small impact angle can generate more uniform global planarization surface but the materials removal rate is lower. The shear interaction between particle and substrate may induce large friction torque and lead to the rotation of particle. The translation plus rotation makes the nanoparticle behaved like micro-milling tool. The results show that the nanoparticles may aggregrate together and form larger cluster thus deteriorate surface the quality. This MD simulation results illuminate that the final planarized surface can only be acquired by synergic behavior of all particles using various means such as cutting, impacting, scratching, indentation and so on.Mechanical polishing (MP), being the important technique of realizing the surface planarization, has already been widely applied in the area of microelectronic manufacturing and computer manufacturing technology. The surface planarization in the MP is mainly realized by mechanical process which depended on the microdynamic behavior of nanoparticle. The complex multibody interaction among nanoparticles and materials surface is different from interaction in the macroscopic multibody system which makes the traditional classical materials machining theory cannot accurately uncover the mystery of the surface generation in the MP. Large-scale classical molecular dynamic (MD) simulation of interaction among nanoparticles and solid surface has been carried out to investigate the physical essence of surface planarization. The particles with small impact angle can generate more uniform global planarization surface but the materials removal rate is lower. The shear interaction between particle and substrate may induce large friction torque and lead to the rotation of particle. The translation plus rotation makes the nanoparticle behaved like micro-milling tool. The results show that the nanoparticles may aggregrate together and form larger cluster thus deteriorate surface the quality. This MD simulation results illuminate that the final planarized surface can only be acquired by synergic behavior of all particles using various means such as cutting, impacting, scratching, indentation and so on.

Keywords: Nanoparticle; Mechanical polishing; Molecular dynamics; Multibody; Complex

Surface reconstruction of ZnO nanowire arrays via solvent-evaporation-induced self-assembly by Fang Fang; Dongxu Zhao; Binghui Li; Zhenzhong Zhang; Dezhen Shen; Xiaohua Wang (pp. 3374-3377).

▶ A solvent-evaporation-induced method was first reported. ▶ Utilize this method, aligned ZnO nanowire arrays reconstruct on large scales. ▶ By changing the concentration of solution, the morphologies of the nanowires can be regulated.Vertically aligned ZnO nanowires (NWs) can be reconstructed on large scales by a solvent-evaporation-induced method. The morphologies of the nanowires are regulated by changing the concentration of the solution. Possible mechanism, which the compressive residual stresses and wires/wires self-attraction can be responsible for the surface reconstruction, is addressed. Furthermore, we compare the structural properties of ZnO nanowires before and after reconstructed.

Keywords: Zno nanowires; Self-assembly

Effect of different modes of electrodeposition on supercapacitive properties of MnO₂ thin films by D.P. Dubal; D.S. Dhawale; T.P. Gujar; C.D. Lokhande (pp. 3378-3382).

▶ Comparison between different modes of electrodeposition. ▶ Effect of different modes on physico-chemical properties of MnO₂ films. ▶ Potential candidate for supercapacitors.In present investigation MnO₂ thin films have been prepared by potentiodynamic (PD), potentiostatic (PS) and galvanostatic (GS) modes of electrodeposition. The effects of different modes on structural, surface morphological and supercapacitive properties of MnO₂ thin films have been investigated. Formation of amorphous phase of MnO₂ by all three modes is confirmed from X-ray diffraction (XRD) patterns. Significant change in the surface morphologies of MnO₂ thin films due to different modes has been observed. The supercapacitive properties of MnO₂ thin films have been studied in 1M Na₂SO₄ electrolyte. The maximum supercapacitance obtained for potentiodynamic, potentiostatic and galvanostatic modes is 237, 196 and 184Fg⁻¹, respectively. Additionally charge–discharge and impedance of MnO₂ thin films have been investigated.

Keywords: Modes of electrodeposition; Surface morphology; Supercapacitor; Charge–discharge; Impedance spectroscopy

Electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy study of the corrosion behaviour of galvanized steel and electroplating steel by M. Lebrini; M. Traisnel; L. Gengembre; G. Fontaine; O. Lerasle; N. Genet (pp. 3383-3387).

▶ In this work, a formula containing 2-{(2-hydroxyethyl)[(4-methyl-1H-1,2,3-benzotriazol-1-yl)methyl]amino}ethanol (tolyltriazole) and decanoic acid have been studied as possible corrosion inhibitor for galvanized steel and electroplating steel in aqueous solution. ▶ X-ray photoelectron spectroscopy also was carried out to complete the study of the electrochemical behaviour of galvanized steel and electroplating steel electrode in aqueous solution in the presence of inhibitor.The efficiency of a formula containing 2-{(2-hydroxyethyl)[(4-methyl-1 H-1,2,3-benzotriazol-1-yl)methyl]amino}ethanol (tolyltriazole) and decanoic acid as corrosion inhibitor for galvanized steel and electroplating steel in aqueous solution have been determined by electrochemical impedance spectroscopy (EIS) techniques. The experimental data obtained from this method show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE) has been used. The corrosion behaviour in the presence of different concentration of decanoic acid (DA) in the formula was also investigated by EIS. Results obtained reveal that, the formula is a good inhibitor for galvanized steel and electroplating steel in aqueous solution, the better performance was obtained in the case of galvanized steel. The ability of the inhibitor to be adsorbed on the surface was dependent on the nature of metal. X-ray photoelectron spectroscopy surface analysis with inhibitor shows that it's chemisorbed at the galvanized and electroplating steel/aqueous solution interface.

Keywords: Tolyltriazole; Decanoic acid; Corrosion inhibitors; Galvanized steel; Electroplating steel; Aqueous solution; X-ray photoelectron spectroscopy

Structure and magnetic properties of flower-like α-NiS nanostructures by Chunjuan Tang; Chunhe Zang; Jianfeng Su; Dongmei Zhang; Guanghai Li; Yongsheng Zhang; Ke Yu (pp. 3388-3391).

▶ This method is environmentally friendly. ▶ Flower-like α-NiS nanostructure has been prepared by a facile one-step hydrothermal method successfully. ▶ The magnetic properties of flower-like α-NiS nanostructure have been studied.In this paper we report the structure and magnetic properties of flower-like α-NiS nanostructure prepared by a facile one-step hydrothermal method. The flowers consist of polycrystalline nanoflakes, and the nanoflakes are composed of single crystalline nanocrystals with an average size of about 15nm. The α-NiS flowers exhibit the transition from paramagnetism to ferromagnetism with the blocking temperature of about 12K. The field dependences of the magnetization prove that these flowers demonstrate a coexistence of antiferromagnetism and ferromagnetism at 5K, and exhibit a strong paramagnetic response at temperature higher than 100K.

Keywords: Inorganic compounds; Nanostructures; Chemical synthesis; Magnetic properties

Desorption of dimethylformamide from Zn₄O(C₈H₄O₄)₃ framework by Lei Zhang; Yun Hang Hu (pp. 3392-3398).

Display Omitted▶ DMF molecules inside the pores of the MOF-5 framework cannot be displaced by CH₂Cl₂. ▶ Desorption of the DMF molecules from the pores of MOF-5 framework requires a temperature of 100°C or above. ▶ Desorption of the DMF molecules from the pores of the MOF-5 framework is the first order with activation energy of 56.38kJ/mol. ▶ DEF molecules can be completely displaced by CH₂Cl₂ during the synthesis of MOF-5, because DEF molecules cannot penetrate into the pores of the MOF-5 paste.Both dimethylformamide (DMF) and diethylformamide (DEF) are important solvents for the synthesis of Zn₄O(C₈H₄O₄)₃ framework (MOF-5). It is generally recognized that DMF molecules can be completely displaced by CH₂Cl₂ during the synthesis of MOF-5. Herein, however, it was found that the DMF molecules inside the pores of the MOF-5 framework cannot be displaced by CH₂Cl₂. The desorption of the DMF molecules from the pores, which requires a temperature of 100°C or above, is the first order with activation energy of 56.38kJ/mol. In contrast, DEF molecules can be completely displaced by CH₂Cl₂ during the synthesis of MOF-5, because DEF molecules cannot penetrate into the pores of the MOF-5 paste.

Keywords: MOF-5; DMF; DEF; Desorption

Surface charging at the (100) surface of Cu doped and undoped Li₂B₄O₇ by Jie Xiao; N. Lozova; Ya.B. Losovyj; D. Wooten; I. Ketsman; M.W. Swinney; J. Petrosky; J. McClory; Ya.V. Burak; V.T. Adamiv; A.T. Brant; P.A. Dowben (pp. 3399-3403).

.Display Omitted▶ The Cu doping suppresses both the hysteresis in photovoltaic charging and the temperature at which surface charging ceases at the surface of lithium tetraborate, a pyroelectric material. ▶ There is either an increase in carrier concentration or carrier lifetimes with Cu doping.We have compared the photovoltaic charging of the (100) surface termination for Cu doped and undoped Li₂B₄O₇. While the surface charging at the (100) surface of Li₂B₄O₇ is significantly greater than observed at (110) surface, the Cu doping plays a role in reducing the surface photovoltage effects. With Cu doping of Li₂B₄O₇, the surface photovoltaic charging is much diminished at the (100) surface. The density of states observed with combined photoemission and inverse photoemission remains similar to that observed for the undoped material, except in the vicinity of the conduction band edge.

Keywords: PACS; 79.60.Ai; 68.55.Ln; 29.40.Wk; 81.05.JOxide dielectric layers; Lithium borate; Surface photovoltaic charging

Formation and structure of sphene/titania composite coatings on titanium formed by a hybrid technique of microarc oxidation and heat-treatment by Su Cheng; Daqing Wei; Yu Zhou (pp. 3404-3411).

▶ Sphene/titania composite coatings were fabricated on titanium by a hybrid technique of microarc oxidation (MAO) and heat treatment. ▶ Heat treatment could change the surface morphology and thickness of the MAO coatings. ▶ The heat-treatment has obvious effect on the chemical states of Si, Ti and O elements but did not affect that of Ca. ▶ In the heat-treated MAO coatings at 800°C, the titanium surface shows a MAO top layer and oxidized interior layer.Sphene/titania composite coatings were fabricated on titanium by a hybrid technique of microarc oxidation (MAO) and heat treatment. The high-applied voltages promote the formation of sphene in the MAO coatings after heat-treatment. Heat treatment could change the surface morphology of the MAO coatings such as roughness, macropores size and density and the thickness of the MAO coatings. Increasing the heat-treatment temperature decreased the atomic concentration ratios of Ti/Si and Ti/Ca of the MAO coatings. The chemical states of Ti⁴⁺, Ca²⁺, Si²⁺ and O²⁻ were observed on all the coatings. Additionally, Ti²⁺ was detected in the MAO and heat-treated MAO coatings at 600 and 700°C. The heat-treatment has obvious effect on the chemical states of Si, Ti and O elements due to the formation of sphene and oxidation of TiO phase of the MAO coating, but did not affect that of Ca. In the heat-treated MAO coatings at 800°C (MAO-H8), the titanium surface shows a MAO top layer and oxidized interior layer. A concentration gradient in components in the MAO layer of the MAO-H8 coating was formed.

Keywords: Titanium; Sphene; Titania; Microarc oxidation; Heat-treatment

Modification of surface layer of magnesium oxide via partial dissolution and re-growth of crystallites by Zhiming Gao; Lingyan Wei; Tingting Yan; Ming Zhou (pp. 3412-3416).

▶ The paper presents a procedure of partial dissolution and re-growth of crystallites for surface modification of metal oxides. ▶ The new MgO surface layer generated by this way had a different crystallinity and reducibility to the original MgO particles, and thus effectively suppressed CO₂ formation in the OCM reaction.A procedure to modify surface layer of metal oxide is presented. By way of partial dissolution and re-growth of crystallites, a new MgO surface layer on the “core” of the original MgO particles was formed. XRD analyses indicate that the new surface layer is different from the original MgO particles in crystallinity. Thus a higher reducibility of surface non-lattice oxygen species is generated. As the extent of dissolution and re-growth of crystallites increased, reducible surface non-lattice oxygen species increased, which led to a lowering of surface non-lattice oxygen concentration on the X%-MgO catalysts in the OCM reaction atmosphere. This is considered to be the major reason for decreasing of CO₂ formation.

Keywords: Surface oxygen; Crystallinity; Magnesium oxide; TPR; OCM

Effect of akermanite morphology on precipitation of bone-like apatite by Xiaoni Hou; Guangfu Yin; Xianchun Chen; Xiaoming Liao; Yadong Yao; Zhongbin Huang (pp. 3417-3422).

▶ Surface morphology of akermanite ceramics may affect precipitation of bone-like apatite. ▶ Rough surface is helpful to precipitation of bone-like apatite. ▶ Suitable surface roughness may improve bioactivity in vitro of akermanite ceramics.Bioactivity in vivo of ceramic materials has been related to their surface micro-topography and may be estimated by means of simulated body fluid method in vitro. In order to investigate the effect of surface topographies of akermanite ceramics on bioactivity in vitro, akermanite ceramics were synthesized by sol–gel method and different surface topographies of disc-shaped akermanite ceramics were prepared by polishing with different SiC sandpapers. Atomic force microscopy (AFM) was used to evaluate the surface morphology and roughness. The bioactivity in vitro of ceramics with different surface states was evaluated by soaking the ceramics in simulated body fluid (SBF). And the samples after being soaked were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). The results showed that the amounts of precipitated apatite on the ceramics with different surface roughness after being soaked in SBF were different and the bioactivity in vitro of ceramic with rough surface was significantly higher than that of ceramic with smooth surface. The study suggested that suitable surface roughness may improve the bioactivity in vitro of akermanite ceramics.

Keywords: Akermanite; Stimulated body fluid; Morphology; Roughness; Atomic force microscopy

Improvement in crystalline quality and surface smoothness of ZnO film by multi-step deposition process by Geun-Hyoung Lee (pp. 3423-3426).

▶ The crystalline quality of ZnO film was improved by multi-step deposition process. ▶ The deposition procedure had an effect on the crystalline quality of ZnO film. ▶ The interval of deposition temperature affected the crystallinity of ZnO film. ▶ The multi-step process is effective for improving the surface roughness of ZnO film.The effect of multi-step deposition process on the crystalline quality and surface smoothness of ZnO film was investigated. ZnO films were composed of multi-layers, in which each layer was deposited at different temperatures. The maximum intensity and the smallest FWHM of (002) diffraction peak in XRD spectrum were observed for the multi-layered ZnO film of which each layer was deposited at progressively higher temperatures. In addition, the smoothest film surface was also observed for the ZnO film deposited through multi-step process in which deposition temperatures gradually increase. On the other hand, the large difference between the deposition temperatures in multi-step process did not result in the significant improvement of the crystalline quality of ZnO film. The ZnO film prepared by using multi-step process had high transmittance over 70% in visible region and the optical band gap of 3.22eV.

Keywords: ZnO film; Multi step deposition; Improvement; Crystalline quality; Surface smoothness

Gallium- and iodine-co-doped titanium dioxide for photocatalytic degradation of 2-chlorophenol in aqueous solution: Role of gallium by Shuang Song; Cheng Wang; Fangyue Hong; Zhiqiao He; Qiaolan Cai; Jianmeng Chen (pp. 3427-3432).

▶ Iodine-doped titanium dioxide photocatalysts are improved by doping with gallium. ▶ Catalysts for degradation of 2-chlorophenol. > 0.5 mol% Ga loading and calcination at 400^oC are optimal preparation conditions. ▶ Ga addition retards the anatase–rutile phase transformation. ▶ Oxygen vacancies may be formed by Ga doping.Visible-light-driven TiO₂-based catalysts for the degradation of pollutants have become the focus of attention. In the present work, iodine-doped titania photocatalysts (I-TiO₂) were improved by doping with gallium (Ga,I-TiO₂) and the resulting physicochemical properties and photocatalytic activity were investigated. The structural properties of the catalysts were determined by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller analysis and transmission electron microscopy. We found that Ga probably enters the TiO₂ framework for doping levels <0.5mol%. A further increase in Ga content probably leads to dispersal of excess Ga on the TiO₂ surface. The photocatalytic activity of Ga,I-TiO₂ catalysts was evaluated using 2-chlorophenol (2-CP) as a model compound under visible and UV–vis light irradiation. The results indicate that 0.5mol% Ga loading and calcination at 400°C represent optimal conditions in the calcining temperature range 400–600°C and with doping levels from 0.1% to 1mol%. The effective enhancement of 2-CP degradation might be attributed to the formation of oxygen vacancies by Ga doping, which could decrease the recombination of electron–hole pairs.

Keywords: TiO; ₂; Iodine; Gallium; Photocatalysis; 2-Chlorophenol; Visible light

Influence of boron concentration on growth characteristic and electro-catalytic performance of boron-doped diamond electrodes prepared by direct current plasma chemical vapor deposition by Yujie Feng; Jiangwei Lv; Junfeng Liu; Na Gao; Hongyan Peng; Yuqiang Chen (pp. 3433-3439).

▶ Our work in this paper reported the preparation of boron-doped diamond (BDD) electrodes by a new chemical vapor deposition technique that was direct current plasma chemical vapor deposition (DC-PCVD). ▶ This technique has been applied in deposition of thick diamond films but was merely investigated in preparing BDD electrodes. ▶ Due to the difficulty of sustaining stable plasma, available reports on the addition of other gases in deposition of doping diamond films by DC-PCVD are very few. ▶ Therefore, we attempted to control the boron dopant concentration and successfully prepared BDD electrodes by this method. ▶ The effects of boron dopant concentration on the growth characteristic and electro-catalytic performance of BDD electrodes had been studied.A series of boron-doped diamond (BDD) electrodes were prepared by direct current plasma chemical vapor deposition (DC-PCVD) with different compositions of CH₄/H₂/B(OCH₃)₃ gas mixture. A maximum growth rate of 0.65mgcm⁻²h⁻¹ was obtained with CH₄/H₂/B(OCH₃)₃ radio of 4/190/10 and this growth condition was also a turning point for discharge plasma stability which arose from the addition of B(OCH₃)₃ that changed electron energy distribution and influenced the plasma reaction. The surface coating structure and electro-catalytic performance of the BDD electrodes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Hall test, and electrochemical measurement and electro-catalytic oxidation in phenol solution. It is suggested that the boron doping level and the thermal stress in the films are the main factors affecting the electro-catalytic characteristics of the electrodes. Low boron doping level with CH₄/H₂/B(OCH₃)₃ ratio of 4/199/1 decreased the films electrical conductivity and its electro-catalytic activity. When the carrier concentration in the films reached around 10²⁰cm⁻³ with CH₄/H₂/B(OCH₃)₃ ratio over a range of 4/195/5–4/185/15, the thermal stress in the films was the key reason that influenced the electro-catalytic activity of the electrodes for its effect on diamond lattice expansion. Therefore, the BDD electrode with modest CH₄/H₂/B(OCH₃)₃ ratio of 4/190/10 possessed the best phenol removal efficiency.

Keywords: Boron-doped diamond; Chemical vapor deposition; Electrochemical oxidation; Phenol

Study of reactions between HfO₂ and Si in thin films with precise identification of chemical states by XPS by H. Wang; P. Wu; X.F. Li; S. Chen; S.P. Zhang; B.B. Song (pp. 3440-3445).

▶ Deposited by r.f. sputtering, HfSiO films with different ratios of Si:Hf could be a combination of hafnium dioxide, hafnium silicate and silicon dioxide. ▶ Annealing in air for 30min, hafnium silicate decomposes above the temperature of 600°C. ▶ With the decomposition of hafnium silicate, the oxygen content in HfSiO films reduces and hafnium silicide forms in the bulk of the films.Reactions between HfO₂ and Si in HfSiO films during deposition and post-annealing have been studied. Intermixing of HfO₂ and Si is achieved by radio frequency sputtering with HfO₂/Si compound targets, and post-annealing is used to promote the reaction at different temperatures. The structural characteristics of the mixture, HfSiO films, are analyzed by X-ray photoelectron spectroscopy and X-ray diffraction, and a careful assessment of chemical states is performed for precise identification. XPS results show that with ratios of Si:Hf ranging from 0 to 0.3 in HfSiO films, Si fully reacts with HfO₂ to form silicate during deposition. However, SiO₂ appears when the ratio of Si:Hf rises to 1.2. When the annealing temperature reaches 600°C, decomposition of hafnium silicate is observed and hafnium silicide forms in the bulk of the films. XRD results reveal that HfSiO films remain amorphous with the annealing temperature below 600°C but crystallize at 800°C.

Keywords: High-κ dielectrics; HfSiO films; X-ray photoelectron spectroscopy; Interfacial reaction

Dependence of resistivity on structure and composition of AZO films fabricated by ion beam co-sputtering deposition by Yu-Yun Chen; Jin-Cherng Hsu; Paul W. Wang; Yao-Wei Pai; Chih-Yuan Wu; Yung-Hsin Lin (pp. 3446-3450).

Display Omitted▶ AZO film fabricated by ion beam co-sputtering deposition at room temperature. ▶ The lowest resistivity of the deposited film is 5.66×10⁻⁴Ω-cm at the 0.7wt.% Al concentration. ▶ The AZO film has a quiet stable thermal stability of the resistivity below 200°C and the lowest resistivity of 4.64×10⁻⁴Ω-cm at 247°C in situ measurement.The correlation between the resistivity and the structure/composition in the aluminum doped zinc oxide (AZO) films fabricated by the ion beam co-sputtering deposition at room temperature was investigated. The various compositions of AZO films were controlled by the sputtered area ratio of Al to Zn target. The structure, Al concentrations and resistivities of the as-deposited films were determined by X-ray diffractometer (XRD), energy dispersive spectrometer (EDS) and four-point probe station, respectively. The lowest resistivity of the deposited film was 5.66×10⁻⁴Ω-cm at the 0.7wt.% aluminum concentration. The most intense ZnO (002) diffraction peak, the largest grain size, the longest mean free path, and the highest free carrier concentration in the film result in the lowest resistivity of 5.66×10⁻⁴Ω-cm at room temperature; simultaneously, the thermal stability of the resistivity of the AZO film as a function of the sample temperature was investigated. Below 200°C the film's resistivity was almost kept at a fixed value and the lowest resistivity of 4.64×10⁻⁴Ω-cm at 247°C was observed.

Keywords: Aluminum doped zinc oxide; AZO; Ion beam co-sputtering deposition; Resistivity; XRD; Thermal stability

Silane effects on the surface morphology and abrasion resistance of transparent SiO₂/UV-curable resin nano-composites by Hsing-I. Hsiang; Yu-Lun Chang; Chi-Yu Chen; Fu-Su Yen (pp. 3451-3454).

▶ The surface microstructure for the transparent SiO₂/UV-curable resin coatings with various MEMO concentrations was investigated. ▶ MEMO/SiO₂ weight ratio increased from 0.2 to 0.6, the dispersion, compatibility and cross-linking density between the MEMO-modified SiO₂ particles and acrylate resin were improved, leading to an increase in abrasion resistance. ▶ As the 3-methacryloxypropyltrimethoxysilane/SiO₂ weight ratio was increased to 1.5, the additional MEMO may exceed that needed to fill the pores with the probability of SiO₂ nano-particles existing on the coating surface was lower than that for samples with a MEMO/SiO₂ weight ratio of 0.6. This produced a decrease in abrasion resistance.Transparent ultraviolet curable nano-composite coatings consisting of nano-sized SiO₂ and acrylate resin have been developed to improve the abrasion resistance of organic polymers. The nano-sized SiO₂ particles were surface-modified using various amounts of 3-methacryloxypropyltrimethoxysilane. The 3-methacryloxypropyltrimethoxysilane concentration effects on the surface morphology and abrasion resistance of the transparent SiO₂/ultraviolet-curable resin nano-composites were investigated using scanning electron microscopy, atomic force microscopy, and ultraviolet-visible spectrophotometer. The results showed that as the 3-methacryloxypropyltrimethoxysilane/SiO₂ weight ratio increased from 0.2 to 0.6, the dispersion, compatibility and cross-linking density between the 3-methacryloxypropyltrimethoxysilane-modified SiO₂ particles and acrylate resin were improved, leading to an increase in abrasion resistance. However, as the 3-methacryloxypropyltrimethoxysilane/SiO₂ weight ratio was increased to 1.5, the additional 3-methacryloxypropyltrimethoxysilane may exceed that needed to fill the pores with the probability of SiO₂ nano-particles existing on the coating surface was lower than that for samples with a 3-methacryloxypropyltrimethoxysilane/SiO₂ weight ratio of 0.6. This produced a decrease in abrasion resistance.

Keywords: Nano-composites; Silane; Abrasion resistance; Microstructure

Preparation of superhydrophobic poly-p-phenylenebenzobisoxazole (PBO) fiber bundles by Zai X. Jiang; Lin Geng; Yu D. Huang (pp. 3455-3462).

▶ A novel PBO fiber with superhydrophobic property was prepared by the combination of rough surfaces and low surface energy material treatment. ▶ The PBO fiber boats cannot only float freely on a water surface but also exhibit large loading capacities, and the highest loading weight, 8.36g, is achieved. ▶ The striking loading capacities of these boats are attributed to the air trapped around the fiber surface.According to the reformed Cassie–Baxter equation, the superhydrophobic phenylenebenzobisoxazole (PBO) fiber bundle boats were fabricated from mimicking the lotus leaf venation using chemical surface modifications and roughness introduction. Water contact angles as high as 152.3° were achieved for PBO fiber bundles. Furthermore, the loading capacities of the superhydrophobic PBO fiber bundle boats were also measured. And the highest loading weight, 8.36g, was obtained by the boats treated with 2.0wt.% (heptadecafluoro-1,1,2,2,-tetradecyl)trimethoxysilane (HFTES). The large loading capacities were believed to arise from the air film surrounding the superhydrophobic surfaces of boats. The results of this study presented new applications of artificial hydrophobic surfaces in areas of miniature aquatic devices.

Keywords: Superhydrophobic surface; PBO fiber bundle; Loading capacities

ZnO:Ag film growth on Si substrate with ZnO buffer layer by rf sputtering by Li Duan; Xiaochen Yu; Lei Ni; Zhuo Wang (pp. 3463-3467).

▶ ZnO buffer layers were used for Ag-doped ZnO films on Si substrates. ▶ The buffer layers relax the partial stress induced by the lattice mismatch between films and substrates. ▶ The properties of Ag-doped ZnO films were effectively improved.ZnO buffer layers were deposited on n-Si (100) substrate by rf magnetron sputtering at a lower power of 40W. Then Ag-doped ZnO (SZO) films were deposited on buffered and non-buffered Si at a higher sputtering power of 100W. The effects of buffer layer on the structural, electrical and optical properties of SZO films were investigated. The three-dimensional island growth process of ZnO buffer layer was discussed. The energy band diagram of p-SZO/ n-Si heterojunction was constructed based on Anderson's model. Results show the ZnO buffer layer leads to better properties of SZO film, including larger grain size, smoother surface, higher carrier mobility, better rectifying behavior, lower interface state density, and weaker deep-level emission. It is because the ZnO buffer layer effectively relaxes the partial stress induced by the large lattice mismatch between SZO and Si.

Keywords: PACS; 68.55.ag; 78.66.Hf; 81.05.DzZnO; Buffer layer; Si substrate; Sputtering

Controlled emission from dye saturated single and coupled microcavities by V.K. Dwivedi; K. Pradeesh; G. Vijaya Prakash (pp. 3468-3472).

▶ We demonstrate modified emission from dye saturated porous silicon microcavities. ▶ Achieved tunable, narrow and enhanced emission from both single and coupled cavities. ▶ Modified emission is from weak coupling of dye emitting states and cavity modes. ▶ Experimental results are successfully supported by transfer-matrix simulations. ▶ Optically active hybrids from low-cost fabrication impart many photonic applications.Modified photoluminescence is demonstrated from the dye saturated porous silicon based single and coupled microcavities. When photonic cavity mode is weakly coupled to the emission states of the dye, photoluminescence line narrowing and intensity enhancement have been observed. Our experimental work and transfer matrix simulations and cavity modelling convincingly explain the tunability and optical field confinement within the microcavity. We also show that the photoluminescence enhancement is due to one-dimensional microcavity effect. These optically active hybrid materials from inexpensive fabrication may become an important consideration for many photonic applications.

Keywords: Optical materials; Porous silicon; Microcavity devices; Photoluminescence

Preparation and characterization of Fe³⁺-doped TiO₂ on fly ash cenospheres for photocatalytic application by Bing Wang; Qin Li; Wei Wang; Ying Li; Jianping Zhai (pp. 3473-3479).

▶ Compared with TiO₂/FAC and Fe–TiO₂, the degradation ratio using Fe–TiO₂/FAC increased by 33% and 30%, respectively. ▶ These synthesized Fe–TiO₂/FAC composites can take advantage of visible light irradiation and can be easily separated from water after the reaction due to their buoyant property. ▶ It's easy and convenient to recycle these catalysts without leaving any decrescence in photocatalytic ability through calcination.Fe³⁺-doped TiO₂ film deposited on fly ash cenosphere (Fe–TiO₂/FAC) was successfully synthesized by the sol–gel method. These fresh photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analyses (TGA). The XRD results showed that Fe element can maintain metastable anatase phase of TiO₂, and effect of temperature showed rutile phase appears in 650°C for 0.01% Fe–TiO₂/FAC. The SEM analysis revealed the Fe–TiO₂ films on the surface of a fly ash cenosphere with a thickness of 2μm. The absorption threshold of Fe–TiO₂/FACs shifted to a longer wavelength compared to the photocatalyst without Fe³⁺-doping in the UV–vis absorption spectra. The photocatalytic activity and kinetics of Fe–TiO₂/FAC with varying the iron content and the calcination temperatures were investigated by measuring the photodegradation of methyl blue (MB) during visible light irradiation. Compared with TiO₂/FAC and Fe³⁺-doped TiO₂ powder (Fe–TiO₂), the degradation ratio using Fe–TiO₂/FAC increased by 33% and 30%, respectively, and the best calcined temperature was 450°C and the optimum doping of Fe/Ti molar ratio was 0.01%. The Fe–TiO₂/FAC particles can float in water due to the low density of FAC in favor of phase separation to recover these photocatalyst after the reaction, and the recovery test shows that calcination contributes to regaining photocatalytic activity of Fe–TiO₂/FAC photocatalyst.

Keywords: Fe; ³⁺; -doped TiO; ₂; Visible light; Fly ash cenosphere; Photocatalytic activity; Sol–gel; Methylene blue (MB)

Plasma modification of self-assembled structures of CoTMPP molecules by N.A. Savastenko; V. Brüser (pp. 3480-3488).

▶ Plasma treatment resulted in rearrangement of CoTMPP self-assemblies. ▶ The large CoTMPP aggregates are split into smaller ones. ▶ The upper layer of CoTMPP aggregates appears to be sublimated after plasma treatment. ▶ Plasma-induced morphological changes can contribute to the enhancement of catalytic activity of treated CoTMPP.Plasma-treated cobalt metalloporphyrins have recently been proposed as electrocatalysts for the oxygen and oxygen peroxide reduction reaction. Whereas the effects of plasma treatment on the elemental composition of the surface of catalysts have been investigated, the effects of plasma treatment on the morphology of catalysts have not yet been studied. In this study, plasma modified nanosized structures of cobalt tetramethoxyphenylporphyrin (CoTMPP) molecules arising from the deposition of a porphyrin solution on an a-C:H film are investigated using an atomic force microscope (AFM). Additionally, the effects of plasma treatment on the structure of porphyrin molecules are studied by using ultra violet visible (UV–vis) absorption analysis. The investigations reveal the morphological changes which accompany the transformation of CoTMPP into the final catalytic material. First, the large CoTMPP aggregates are split into smaller ones. Second, the CoTMPP layer appears to be sublimated after plasma treatment. Sublimated CoTMPP molecules can be decomposed by plasma and after redeposition can form catalytic active fragments.

Keywords: PACS; 52.40.Hf; 68.37.Ps; 68.55.J−Plasma treatment; Porphyrin; Catalysts; Self-assembly; Atomic force microscopy

Enhanced fibroblast cell adhesion on Al/Al₂O₃ nanowires by O.C. Aktas; M. Sander; M.M. Miró; J. Lee; C.K. Akkan; H. Smail; A. Ott; M. Veith (pp. 3489-3494).

▶ A single-step deposition process (without any catalyst) is applied to synthesize Al/Al₂O₃ bi-phasic nanowires. ▶ Al/Al₂O₃ bi-phasic nanowires substantially promote the fibroblast adhesion. ▶ The measured adhesion is very strong and comparable with that on bioorganic layers.Biological cells stick together via transmembrane proteins, which are linked to receptor molecules of the extracellular matrix (ECM). This specific biochemical adhesion plays a leading role in many cellular processes, among them cell differentiation, morphogenesis, and wound healing. Various medical applications require endogen cells to bind to an exogene substrate as in the case of an implant. Coatings with proteins that naturally belong to the ECM are known to enhance the cell adhesion. However, the choice of inorganic materials, which promote cell adhesion, is limited. Here, we report on a new engineered surface composed of Al/Al₂O₃ bi-phasic nanowires (NWs), which promotes the adhesion of fibroblast cells. Fibroblasts grow well on this inorganic layer and keep proliferating. Using the cell monolayer rheology (CMR) technique, we show that the adhesion of fibroblasts on Al/Al₂O₃ NWs is comparable to fibronectin coated surfaces. To our knowledge, this is one of the strongest cell adhesions on an inorganic surface, which has been reported on so far, since it compares to bio-organic layers such as fibronectin.

Keywords: Nanowires; Single source precursor; Chemical vapor deposition; Cell adhesion; Dynamic mechanical analysis; Rheology

Upconversion luminescence from Er-N codoped of ZnO nanowires prepared by ion implantation method by Kun Zhong; Jie Xu; Jing Su; Yu lin Chen (pp. 3495-3498).

▶ Nitrogen and erbium co-doped of ZnO nanowires (NWs) are fabricated by ion implantation and subsequent annealing in air. The enhancement of the PL intensity by the N-doped is caused by the formation of ErO6−_xN_x octahedron complexes. With the increase of the T_a, the Er³⁺ ions diffuse towards the surface of the NWs, which benefits the red emission owing to the existence of some organic groups.Nitrogen and erbium co-doped of ZnO nanowires (NWs) are fabricated by ion implantation and subsequent annealing in air. The incorporation of Er³⁺ and N⁺ ions is verified by energy dispersive X-ray spectroscopy (EDS) and Raman spectra. The samples exhibit upconversion photoluminescence around ∼550nm and ∼660nm under an excitation at 980nm. It is discovered that the N-doped can drastically increase the upconversion photoluminescence intensity by modifying the local structure around Er³⁺ in ZnO matrix. The enhancement of the PL intensity by the N-doped is caused by the formation of ErO6−_xN_x octahedron complexes. With the increase of the annealing temperature ( T_a), the Er³⁺ ions diffuse towards the surface of the NWs, which benefits the red emission and evokes the variation of intensity ratio owing to the existence of some organic groups.

Keywords: Er-N co-doped; ZnO nanowires; Upconversion photoluminescence

Preparation and surface encapsulation of hollow TiO nanoparticles for electrophoretic displays by Qian Zhao; Tingfeng Tan; Peng Qi; Shirong Wang; Shuguang Bian; Xianggao Li; Yong An; Zhaojun Liu (pp. 3499-3503).

▶ Hollow black TiO nanospheres were obtained via polymer latex templating procedure with Ti(OBu)₄ as precursor. ▶ To increase lipophilic degree, a better encapsulation was achieved by pretreating the TiO particles with 3-(trimethoxysilyl) propyl methacrylate. ▶ Glutin-gum Arabic electrophoretic microcapsules were prepared via complex coacervation. ▶ The results showed that the TiO–KH570–PS nanoparticles responded to electric field and to electrodes.Hollow black TiO nanosparticles were obtained via deposition of inorganic coating on the surface of hollow core–shell polymer latex with Ti(OBu)₄ as precursor and subsequent calcination in ammonia gas. Hollow TiO particles were characterized by scanning electron microscope, transmission electronic microscopy, X-ray diffraction, and thermogravimetric analysis. Encapsulation of TiO via dispersion polymerization was promoved by pretreating the pigments with 3-(trimethoxysilyl) propyl methacrylate, making it possible to prepare hollow TiO-polymer particles. When St and DVB were used as polymerization monomer, hollow TiO-polymer core–shell particles came into being via dispersion polymerization, and the lipophilic degree is 28.57%. Glutin-arabic gum microcapsules containing TiO-polymer particles electrophoretic liquid were prepared using via complex coacervation. It was founded that hollow TiO-polymer particles had enough electrophoretic mobility after coating with polymer.

Keywords: Hollow TiO nanoparticles; Surface encapsulation; Electrophoretic properties; Microcapsules

Rapid formation of tungsten oxide nanobundles with controllable morphology by Y.T. Hsieh; U.S. Chen; S.H. Hsueh; M.W. Huang; H.C. Shih (pp. 3504-3509).

▶ W₁₈O₄₉ nanobundles with controllable morphology were fabricated on Si substrates by MPECVD. ▶ The morphology of the nanobundles can be controlled by adjusting the reaction times. ▶ Nanowires DIA: 15–30nm, nanorods DIA: 40–60nm, nanoslabs THK: 30nm were formed at 1.5, 3, and 4min. ▶ MPECVD is highly effective and suitable for fabrication of various tungsten oxide nanobundles.Tungsten oxide (W₁₈O₄₉) nanobundles with controllable morphology were fabricated on Si substrates within 5min by microwave plasma-enhanced chemical vapor deposition (MPECVD). The crystal structure and chemical composition of these nanobundles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). The results of these characterizations confirmed the formation of W₁₈O₄₉ nanobundles with [010] as the major growth direction. SEM images showed that the nanobundles were several micrometers long with diameters of 20–500nm. The morphology of the nanobundles can be controlled by simply adjusting the reaction times to the desired level; nanowires (diameter: 15–30nm), nanorods (diameter: 40–60nm), and nanoslabs (thickness: 30nm) were formed at 1.5, 3, and 4min, respectively. With an increase in reaction times, the nanobundles steadily increased in dimensions to form nanoslabs. Thus, our results indicated that MPECVD is highly effective and suitable for fabrication of various tungsten oxide nanobundles.

Keywords: Tungsten oxide nanobundles; Rapid formation; Controllable morphology

Ultra thin films of gadolinium deposited by evaporation in ultra high vacuum conditions: Composition, growth and morphology by O.A. Herrera-Sancho; D. Castro-González; J.A. Araya-Pochet; W.E. Vargas-Castro (pp. 3510-3518).

▶ Conditions to accomplish deposition of ultra thin metal films of Gd were reached. ▶ Ultra thin films with low contamination levels were obtained. ▶ Chemical characterization of the films was carried out. ▶ Morphology of the metal island films was characterized from AFM analysis. ▶ AFM data and presence of oblate spheroid caps of Gd is established are correlated. ▶ Sticking coefficient of Gd/quartz and Gd/Gd, and contact angles, are reported.Ultra-thin gadolinium films with thicknesses between 8 and 101Å were deposited on AT-cut crystalline quartz substrates under ultra high vacuum conditions, and subsequently subjected to composition and morphologic characterization through X-ray photo-spectroscopy analysis and atomic force microscopy. Oxygen contamination is found on the samples, and its amount is estimated in terms of the thickness of an oxygen layer over the gadolinium films after subtracting the contribution to the XPS spectra of the underlying background. Atomic force microscope pictures provide evidence of having metal island films, with two growing regimes: the Volmer–Weber mode for the thinner films considered and the Stranski–Krastanov growing mode for the thicker ones. From evaluation of the sticking coefficient, the shape of the islands is approximated in terms of oblate spheroid caps and variation of the contact angle with film mass thickness is reported.

Keywords: Metal island films; Ultra thin films; Growing modes; Film morphology

Effect of emulsifier content of sizing agent on the surface of carbon fibres and interface of its composites by R.L. Zhang; Y.D. Huang; L. Liu; Y.R. Tang; D. Su; L.W. Xu (pp. 3519-3523).

▶ First report about the influence of emulsifier content of sizing agent. ▶ The emulsifier content of sizing agent has an important influence to carbon fibres. ▶ The sizing agent has an important influence to the carbon fibres composites. ▶ This research has concluded that E-3 sized carbon fibres showed better properties. ▶ The sizing agent E-2 sized carbon fibre has better ageing resistant properties.In this work, carbon fibres were sized with different emulsifier content sizing agent in order to improve the performances of carbon fibres and the interface of carbon fibres composites. The surface characteristic changing after modification was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM). Wetting and surface energy along with contact angles were determined by the dynamic contact angle analysis test (DCAT). At the same time, the single fibre strengths and weibull distributions were also studied in order to understand the effect of the emulsifier content of sizing agent on the carbon fibres. The interfacial shear strength and hygrothermal ageing of the composites were measured which showed a different enhancement, respectively. The results revealed that sizing agent E-3 showed better interface adhesion between fibres and matrix and sizing agent E-2 sized carbon fibre has better ageing resistant properties.

Keywords: Carbon fibres; Interfacial strength; Coating; Hygrothermal effect

Adsorption of methyl orange on mesoporous γ-Fe₂O₃/SiO₂ nanocomposites by W. Deligeer; Y.W. Gao; S. Asuha (pp. 3524-3528).

▶ A template-free sol–gel method can produce mesoporous γ-Fe₂O₃/SiO₂ nanocomposite. ▶ Gaseous species play an important role in the formation of mesoporous structure.▶ Mesoporous γ-Fe₂O₃/SiO₂ has a large adsorption capacity for methyl orange. ▶ Methyl orange sorption can be well described by both Langmuir and Freundlich models.Mesoporous γ-Fe₂O₃/SiO₂ nanocomposite containing 30mol% of γ-Fe₂O₃ was prepared by a template-free sol–gel method, and its removal ability for methyl orange (MO) was investigated. The nanocomposite was characterized using X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared (FTIR) absorption measurements, nitrogen adsorption–desorption measurements, and magnetic measurements. The synthesized γ-Fe₂O₃/SiO₂ nanocomposite has a mesoporous structure with an average pore size of 3.5nm and a specific surface area of 245m²/g, and it exhibits ferrimagnetic characteristics with the maximum saturation magnetization of 20.9emu/g. The adsorption of MO on the nanocomposite reaches the maximum adsorbed percentage of ca. 80% within a few minutes, showing that most of MO can be removed in a short time. The MO adsorption data fit well with both Langmuir and Freundlich adsorption isotherms. The maximum adsorption capacity of MO is estimated to be 476mg/g.

Keywords: Maghemite; Nanocomposite; Adsorption; Methyl orange

The characteristics of chromized 1020 steel with electrical discharge machining and Ni electroplating pretreatments by Ching-Yuan Bai; Jeou-Long Lee; Tse-Min Wen; Kung-Hsu Hou; Min-Sheng Wu; Ming-Der Ger (pp. 3529-3537).

▶ Characteristics of the AISI 1020 steel through pack chromization with pretreatments. ▶ The performance of the chromized coatings in the simulated environments of PEMFCs. ▶ The chromized coatings contain chromium carbides mostly and some chromium nitrides. ▶ Promoting the corrosion resistance and surface conductivity of AISI 1020 steels.A uniform and continuous chromized coating on AISI 1020 steel is produced by low-temperature pack chromization (LTPC) with electrical discharge machining and Ni electroplating pretreatments. The anticorrosive performance of the chromized steels is investigated in a 0.5M H₂SO₄ solution at room temperature. The testing results indicate that the chromized specimen with electrical discharge machining and Ni electroplating pretreatments exhibits the lowest corrosion current density, 2.16×10⁻⁸Acm⁻², among the tested specimens. The corrosion resistance of all tested specimens are in the order of bare 1020<1020-Cr(700-2)<1020-Ni–Cr(700-2)<1020-EDM-Ni–Cr(700-2). Moreover, the 1020-Ni–Cr(700-2) specimen have the best conductivity as a result of the less amount of oxides in the superficial coating.

Keywords: AISI 1020 steel; Low-temperature pack chromization; Electrical discharge machining; Electroplating; Corrosion current density

“Versatile toolset” for DNA or protein immobilization: Toward a single-step chemistry by Thomas Berthelot; Alexandre Garcia; Xuan Tuan Le; Jenna El Morsli; Pascale Jégou; Serge Palacin; Pascal Viel (pp. 3538-3546).

Display Omitted▶ Covalent immobilization of non-modified protein or nucleic acid materials. ▶ Self-adhesive primer for immobilizing biological materials from aqueous solutions. ▶ Ink or UV masking patterning method for multianalyte chemosensor or biosensors. ▶ Chemical grafting of diverse biological materials on diverse substrates. ▶ Green and soft procedure for chemical surface modification of diverse substrates.Covalent immobilization of non-modified biological materials as proteins or nucleic acids has been performed through a single and soft method. Based on diazonium salt chemistry, this protocol leads to an ultrathin grafted film, on metallic or polymer materials, which can eventually be used as a self-adhesive primer for immobilizing biological materials from aqueous solutions through a simple dipping step. Moreover, this self-adhesive primer may be patterned by cheap and easy methods as ink or UV masking. Biological models as low molecular weight DNA from salmon sperm and glucose oxidase (GOD) were covalently immobilized by this soft procedure. In order to evaluate the consequences of this non-specific covalent immobilization method on biological activity, enzymatic activity of GOD was monitored by electrochemical detection of hydrogen peroxide (H₂O₂). We thus demonstrate that such a self-adhesive primer represents a new and alternative process offering a versatile toolset for immobilizing biological material for biosensor development on conductive and non-conductive materials.

Keywords: Biosensor; DNA; Protein; Covalent immobilization of biomolecule; Diazonium salt; Surface chemistry

Wettability modification of electrospun poly(ɛ-caprolactone) fibers by femtosecond laser irradiation in different gas atmospheres by Lingna He; Jian Chen; Dave F. Farson; John J. Lannutti; Stan I. Rokhlin (pp. 3547-3553).

▶ The wettability of electrospun poly(ɛ-caprolactone) nanofiber tissue scaffolds was modified by femtosecond laser irradiation in air and with O₂ and CF₄ gas flows. ▶ Surface water contact angle continuously decreased with increased oxygen atomic percentage and oxygen-containing group fraction. ▶ Of the three gas atmospheres, O₂ gas flow was the most favorable environment for increasing surface oxidization, resulting in the largest water contact angle decrease for given laser power.The effect of femtosecond laser irradiation in air and in O₂ and CF₄ gas flows on the wettability of electrospun poly(ɛ-caprolactone) fiber tissue scaffolds was studied. Laser power, focus spot size, raster scan spacing and gas atmosphere were varied in experiments. SEM imaging showed the average fiber diameter and surface porosity sizes were both altered by ablation. The micro-scale surface roughness measured by scanning laser profilometry was found to have a non-monotonic relationship to the surface wettability measured by the contact angle of sessile water droplets. In contrast, surface water contact angle continuously decreased with increased oxygen atomic percentage and oxygen-containing group fraction as measured by XPS. Further, the oxygen content was larger for more extensively ablated fiber surfaces, regardless of whether the increased ablation was caused by high laser power, smaller scanning space or smaller defocusing distance. Of the three gas atmospheres, O₂ gas flow was the most favorable environment for increasing surface oxidization, resulting in the largest water contact angle decrease for given laser power. For CF₄ gas flow, the least oxidization occurred, and the magnitude of water contact angle decrease was smallest for treatment at a given laser power.

Keywords: Wettability; Poly(ɛ-caprolactone); Electrospun polymer tissue scaffold; Fiber; Femtosecond laser ablation

Effect of Ni-to-Fe ratio on structure and properties of Ni–Fe–B–Si–Nb coatings fabricated by laser processing by Ruifeng Li; Zhuguo Li; Jian Huang; Peilei Zhang; Yanyan Zhu (pp. 3554-3557).

▶ Ni–Fe–B–Si–Nb coatings were deposited on steel substrates using laser processing. ▶ Amorphous matrix layers were obtained for all coatings. ▶ Properties of coating with 1:1 ratio of Ni-to-Fe exhibits superior than others.Ni–Fe–B–Si–Nb coatings have been deposited on mild steel substrates using high power laser cladding process followed by laser remelting. The influence of Ni-to-Fe concentration ratio in (Ni100−_xFe_x)₆₂B₁₈Si₁₈Nb₂ ( x=55, 50, 45 and 40) powders on the phase composition and microstructure is analyzed by X-ray diffraction, scanning- and transmission-electron microscopies. The microhardness and corrosion resistance properties of the coatings are also measured. The results reveal that amorphous matrix layers are obtained for all coatings. The increase of the Ni-to-Fe ratio can promote the formation of γ(Fe–Ni) phase and decrease the formation of Fe₂B phase and α-Fe phase. The coating with 1:1 ratio of Ni-to-Fe exhibits the highest microhardness of 1200HV_0.5 and superior corrosion resistance property due to its largest volume fraction of amorphous phase in the coating. Higher or lower than 1:1 ratio of Ni-to-Fe may result in lower amorphous forming ability. However, even that the coating with ratio of 3:2, shows a minimum of microhardness, it shows a better corrosion resistance than other two coatings.

Keywords: Laser cladding; Remelting; Ni–Fe–B–Si–Nb; Amorphous; Coating

Effects of thermo-hygro-mechanical densification on the surface characteristics of trembling aspen and hybrid poplar wood veneers by Papa Niokhor Diouf; Tatjana Stevanovic; Alain Cloutier; Chang-Hua Fang; Pierre Blanchet; Ahmed Koubaa; Nicolas Mariotti (pp. 3558-3564).

▶ Veneer color darkened with increasing THM densification temperature. ▶ Surface roughness decreased between 160°C and 200°C. ▶ Wettability decreased after THM densification. ▶ THM densification caused major chemical changes in veneer surfaces.The effect of thermo-hygro-mechanical (THM) densification temperature on the surface color, roughness, wettability, and chemical composition of trembling aspen ( Populus tremuloides) and hybrid poplar ( Populus maximowiczii× P. balsamifera) veneers was investigated. Veneers were subjected to four THM densification temperatures (160°C, 180°C, 200°C, and 220°C). Veneer color darkened with increasing THM densification temperature. Surface roughness decreased between 160°C and 200°C. Wettability decreased after THM densification, but no significant difference was found between treated specimens. ATR-FTIR and XPS results confirmed that THM densification caused major chemical changes in veneer surfaces, and more pronounced at temperatures higher than 160°C.

Keywords: Populus; sp. veneer; Thermo-hygro-mechanical densification; Surface color; Surface roughness; Surface wettability; Surface chemistry

Electrical and structural properties of a stacked metal layer contact to n-InP by Wen-Chang Huang; Chia-Tsung Horng (pp. 3565-3569).

▶ The formation of a Al₂O₃ layer at the contact interface of the Pt/Al/n-InP diode was observed by XRD and SIMS analyses. ▶ The formation of the Al₂O₃ interfacial layer improved the Schottky barrier height of the Pt/Al/InP diode. ▶ The distribution of local effective Schottky barrier heights was explained by a model incorporating the existence of double Gaussian barrier heights.In this study, we found that the double metal contact structure in Pt/Al/ n-InP diodes provides better rectification characteristics than conventional single-metal/ n-InP Schottky diodes. The effective barrier height was measured to be 0.67eV for a 400°C-annealed Pt/Al/ n-InP diode sample. The increase in the barrier height is attributed to the formation of Al₂O₃ at the metal/ n-InP contact interface during thermal annealing. The formation of the phase Al₂O₃ phase was monitored by X-ray diffraction (XRD) analysis. The corresponding element profiles of Al and O were also confirmed at the metal/ n-InP contact interface using secondary ion mass spectrum (SIMS) analysis. The lowering of the Schottky barrier height due to the inhomogeneity at the metal/ n-InP junction is also discussed on the basis of the TE theory. The distribution of local effective Schottky barrier heights was explained by a model incorporating the existence of double Gaussian barrier heights, which represent the high barrier and low barrier of the full distribution in the temperature ranges of 83–198 and 198–300K.

Keywords: InP; Al; ₂; O; ₃; Schottky barrier inhomogeneity

Pulsed laser deposition of semiconducting crystalline double-doped barium titanate thin films on nickel substrates by I. Apostol; N. Stefan; C.R. Luculescu; R. Birjega; M. Socol; M. Miroiu; I.N. Mihailescu (pp. 3570-3576).

▶ We extended the application of pulsed laser deposition to the synthesis of two types of cubic double-doped BaTiO₃ (Sr,Y and respectively Pb,Y) thin films with semiconducting properties, for microelectronics applications, on nickel substrates. ▶ The semiconducting behavior was proved by measurements of electrical resistance vs temperature.We synthesized by pulsed laser deposition (Ba,Sr,Y)TiO₃ and (Ba,Pb,Y)TiO₃ thin films on mechanically polished nickel substrates.The synthesized thin films were analyzed for: crystalline structure by X-ray diffractometry, morphology and surface topography by atomic force microscopy, optical and scanning electron microscopy, and elemental composition by energy dispersive X-ray spectroscopy and electrical properties by electrical measurements.We have shown that film properties were determined by the dopants, target composition, and deposition parameters (oxygen pressure, substrate temperature and incident laser fluence). All films exhibited a semiconducting behavior, as proved by the decrease of electrical resistance with heating temperature.

Keywords: Thin films; Semiconducting material; Laser processing

Model calculation of the surface tension of liquid Ga–Bi alloy by Fathi Aqra; Ahmed Ayyad; Fahed Takrori (pp. 3577-3580).

▶ Model for calculating surface tension of alloys is presented. ▶ Results are in agreement with existing experimental data. ▶ Described method supports measured observations. ▶ Calculations are of major significance in the field of surface science.A convenient model, based on some assumptions, for calculating the composition and temperature dependence of the surface tension of binary liquid alloys is reported. The theoretical calculations of the surface tension of gallium-rich-bismuth alloys are presented. The calculated results are compared with the reported experimental data. A relatively good agreement with experimental behavior of the composition dependence of the surface tension was found, but a disagreement was observed with experimental temperature behavior of the surface tension of these alloys. The calculations were conducted in the temperature range from almost 320K to about 800K. The surface tension was calculated from eutectic composition ( x_Bi=0.0022) to x_Bi=0.1, and worked out by linear equations. The model calculation and analysis indicate a first order surface phase transition in this system, which is in accord with experimental findings. For this system, γ decreases linearly with increasing temperature at fixed Bi mole fraction x_Bi, and thus, suggesting a positive surface excess entropy. It is also found that the surface tension isotherms show the linear dependence on the concentration, in the logarithm scale of x_Bi, in the very narrow concentration range.

Keywords: Surface tension; Binary liquid alloy; Materials

Ab initio study of the fcc-WC(100) surface and its interaction with cobalt monolayers by V.G. Zavodinsky (pp. 3581-3585).

▶ The free WC(100) surface undergoes a relaxation: carbon atoms moved outward, while tungsten atoms moved inward. ▶ The monolayer layers of cobalt with atoms positioned above carbon atoms are energetically preferable. ▶ Co layers are ferromagnetic, however, the magnetization does not influence essentially their energetics and geometry.The WC(100) surface has been studied by using ab initio methods of the density functional theory and pseudopotentials. Calculations have shown that surface and undersurface atoms move from their bulk positions. Namely, carbon atoms moved outward, while tungsten atoms moved inward. Five geometric cases for Co/WC(100) system were compared: (A) Co atoms are above C atoms; (B) Co atoms are above W atoms; (C) Co atoms are in the four-fold sites above WC pairs; (D and E) Co atoms are above the W–W–C and C–C–W three-fold sites, respectively – and the (A) case has been found to be energetically preferable. In all cases, Co layers have been found to be ferromagnetic. The densities of states for the bulk fcc-WC, the WC(100) surface, and the WC/Co system were compared.

Keywords: Tungsten carbide; WC(1; 0; 0) surface; Cobalt monolayer; Ab initio calculations

Synthesis of submicron rhombic ZnO rods via ZnOHF intermediate using electrodeposition route by Min Dai; Feng Xu; Yinong Lu; Yunfei Liu; Yan Xie (pp. 3586-3591).

▶ Different morphologies of ZnOHF films have been prepared in the paper. ▶ A possible mechanism for the conversion from ZnOHF to ZnO crystals was suggested. ▶ The role of fluoride ion in the electrodeposition process has been investigated.ZnOHF submicron rods with the rhombus-like shape were successfully prepared by a low-temperature aqueous electrodeposition route. By further adjusting the experimental parameters including the electrolyte concentration, temperature, the electrodeposition potential, and the duration, the morphologies of ZnOHF films can further be controlled; accordingly, ZnO films with different morphologies were also obtained by calcining ZnOHF intermediate at 400°C for 2h. Based on the experimental results, a plausible mechanism for the conversion from ZnOHF to ZnO crystals was proposed. The surface morphology and microstructure of the products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the optical property of the samples was investigated by room-temperature photoluminescence (PL) spectra as well. The PL spectra confirmed that ZnOHF and ZnO exhibited emission band centered at 413nm and 382nm in UV region, respectively.

Keywords: ZnOHF; ZnO; Rhombus-like rod; Electrodeposition; Photoluminescence

Facile synthesis of well-dispersed SrF₂:Yb³⁺/Er³⁺ upconversion nanocrystals in oleate complex systems by Jiayue Sun; Jianbo Xian; Haiyan Du (pp. 3592-3595).

▶ In this paper, to our knowledge, it is first time that well oil-dispersible SrF₂:Yb³⁺/Er³⁺ nanocrystals have been successfully prepared in the water–ethanol–oleic acid–sodium oleate complex systems. ▶ The size and shape of the NCs were controlled by adjusting the amount of OA/NaOA, temperature and reaction time. ▶ A systematic study on the photoluminescence of Yb³⁺/Er³⁺-doped SrF₂ samples with different size and shapes has shown that the optical properties of products are strongly dependent on their size.Well oil-dispersible SrF₂:Yb³⁺/Er³⁺ upconversion (UC) nanocrystals (NCs) were easily synthesized in the water–ethanol–oleic acid–sodium oleate complex systems. The as-prepared NCs all show size-uniformity, and their sizes, morphologies can be controlled by varying the solvent and reaction time, and rectangular SrF₂:Yb³⁺/Er³⁺ nanosheets with the sizes of 5–25nm can be obtained. The possible mechanism on the nucleation and growth of nanocrystals occurred at the oleic acid/sodium oleate interface was also discussed. The size and morphology dependent UC luminescence behaviors have been observed in SrF₂:Yb³⁺/Er³⁺ NCs, and their UC luminescence transitions were proposed. The as-prepared UC nanocrystals are expected to fulfill the demand for biological applications.

Keywords: Nanomaterials; Morphology; Optical properties; Upconversion

Hydrophobisation of activated carbon fiber and the influence on the adsorption selectivity towards carbon disulfide by Zunyuan Xie; Feng Wang; Ning Zhao; Wei Wei; Yuhan Sun (pp. 3596-3602).

▶ The vinyltrimethoxysilane (vtmos) was grafted onto the surface of commercial viscose-based activated carbon fiber. ▶ The existence of the silicone group enhanced the hydrophobicity of carbon surface and lowered the harmful influence on the adsorption of carbon disulfide induced by water. ▶ The enhancement of the hydrophobicity improved the adsorption selectivity towards carbon disulfide in high humid.The hydrophobisation of commercial viscose-based activated carbon fiber (ACF) was obtained by grafting vinyltrimethoxysilane (vtmos) on the ACF surface, to improve ACF's adsorption selectivity towards carbon disulfide (CS₂) under highly humid condition. The characterizations, including FTIR,²⁹Si NMR, adsorption/desorption of nitrogen, thermal analysis and elemental analysis, revealed that the vtmos was successfully grafted onto the ACF surface, even though the hydrophobisation caused a partial filling of the porosity along with a slight decrease in the surface area. The efficiency of the hydrophobisation modification was evaluated by both equilibrium and dynamic adsorption experiment of water vapor and CS₂. The equilibrium adsorption results indicated that the hydrophobisation modifications accounted for a decrease of both the amounts of water and CS₂ adsorbed by the hydrophobised ACF. However, dynamic adsorption found that the adsorption performance was improved under highly humid condition, evidencing that hydrophobisation improved the hydrophobicity of the ACF surface and enhanced the adsorption selectivity towards CS₂.

Keywords: Hydrophobisation; Activated carbon fiber; Vinyltrimethoxysilane; Carbon disulfide; Selective adsorption

Potential barrier generation at the BeW interface blocking thermonuclear radiation by Yan Wang; Yanguang Nie; L.K. Pan; Zhuo Sun; Chang Q. Sun (pp. 3603-3606).

The establishment of interface potential barrier and the associated valance charge polarization of BeW alloy has been revealed to be responsible for the thermonuclear fusion radiation protection.Display Omitted▶ Valence charge polarization and the interface potential barrier creation of BeW alloy could screen the thermonuclear radiation in fusion devices.BeW is an important medium for radiation protection in the International Thermonuclear Experimental Reactor (ITER) devices. However, the mechanism for the radiation-protection ability of BeW remains unclear. An extension of the BOLS correlation mechanism into the X-ray photoelectron spectroscopy (XPS) has enabled us to examine the energy and charge distribution of the specimen and clarify that the Be 1s and W 4f_7/2 energy levels undergo an elevation by 0.136 and 0.184 times those of the respective bulk constituents standing alone up-on BeW compound formation associated with polarization of the valence density of states. It is suggested that the interface potential barrier creation due to bond order distortion and bond nature alteration perturbs essentially the Hamiltonian and hence leads to the binding energy shifts. The established interface potential barrier and the polarized charge may screen the nuclear irradiation in the thermonuclear fusion devices. Findings may provide guideline for searching materials for such purpose.

Keywords: Potential barrier; Alloy; Binding energy shift

Local super-saturation dependent synthesis of MgO nanosheets by Luwei Sun; Haiping He; Chao Liu; Zhizhen Ye (pp. 3607-3611).

▶ MgO nanowires and nanosheets are simultaneously synthesized. ▶ Local super-saturation is responsible for different morphology. ▶ The nanosheets are preferably grown on the plane with low surface energy.Well-crystallized MgO nanosheets have been prepared with MgB₂ as a precursor without any catalyst via a simple chemical vapor deposition (CVD) method. The nanosheets are grown parallel to (200) plane according to the high-resolution transmission electron microscopy profiles. At the same time, MgO nanowires are formed in the different area of substrate, which is the result of the difference in local super-saturation. Consequently, we propose that the growth mechanism depends on the surface energy and the local super-saturation in the system.

Keywords: Magnesium oxide; Chemical vapor deposition; Surface energy; Nanostructures; Super-saturation

Electrochemically assisted co-deposition of calcium phosphate/collagen coatings on carbon/carbon composites by Xueni Zhao; Tao Hu; Hejun Li; Mengdi Chen; Sheng Cao; Leilei Zhang; Xianghui Hou (pp. 3612-3619).

▶ CaP/collagen coatings were prepared on the surface of C/C composites. ▶ The surface of three-dimensional collagen network was covered by uniform CaP aggregates. ▶ HA was a favorable composition in the coatings with the increasing of collagen concentration. ▶ Adhesive strength of the coatings increased as the collagen concentration increased. ▶ Nano-structured HA/collagen coatings similar to the natural human bone were obtained on the C/C.Calcium phosphate (CaP)/collagen coatings were prepared on the surface of carbon/carbon (C/C) composites by electrochemically assisted co-deposition technique. The effects of collagen concentration in the electrolyte on morphology, structure and composition of the coatings were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The adhesive strength of the coatings was also evaluated by scratch tests and tensile bond tests. It was demonstrated that the coatings of three-dimensional collagen network structure was formed on the C/C composites from the electrolyte containing collagen. The surface of the collagen network was covered by uniform CaP aggregates. The coatings were actually composites of CaP and collagen. Hydroxyapatite (HA) was a favorable composition in the coatings with the increase of the collagen concentration in the electrolyte. The formed collagen network increased the cohesive and adhesive strength of the coatings. The adhesive strength between the coatings and substrates increased as the collagen concentration in the electrolyte increased. The coatings prepared at the collagen concentration of 500mg/L in the electrolyte were not scraped off until the applied load reached 32.0±2.2N and the average tensile adhesive strength of the coatings was 4.83±0.71MPa. After C/C coated with composite coatings (500mg/L) being immersed in a 10⁻³M Ca (OH)₂ solution at 30–33°C for 96h, nano-structured HA/collagen coatings similar to the natural human bone were obtained on the C/C.

Keywords: Electrochemically assisted deposition; Calcium phosphate; Hydroxyapatite; Adhesive strength; Collagen; C/C

Effect of multi-walled carbon nanotubes loaded with Ag nanoparticles on the photocatalytic degradation of rhodamine B under visible light irradiation by Ya Yan; Huiping Sun; Pingping Yao; Shi-Zhao Kang; Jin Mu (pp. 3620-3626).

▶ The visible light photocatalytic activity of Ag/MWNTs was explored. ▶ Electrochemical impedance spectroscopy (EIS) was applied to characterize the electron transfer rate of Ag/MWNTs. ▶ Ag/MWNTs was found to be an ideal alternative to Pt/MWNTs for the rhodamine B degradation due to its low cost and high visible light photocatalytic activity.Multi-walled carbon nanotubes loaded with Ag nanoparticles (Ag/MWNTs) were prepared by two methods (direct photoreduction and thermal decomposition). The photocatalytic activity of Ag/MWNTs for the degradation of rhodamine B (RhB) under visible light irradiation was investigated in detail. The adsorption and photocatalytic activity tests indicated that the MWNTs served as both an adsorbent and a visible light photocatalyst. The photocatalytic activity of MWNTs was remarkably enhanced when the Ag nanoparticles were loaded on the surface of MWNTs. Moreover, the visible light photocatalytic activity of Ag/MWNTs depended on the synthetic route. On the basis of the experimental results, a possible visible light photocatalytic degradation mechanism was discussed.

Keywords: Multi-walled carbon nanotubes; Silver; Adsorption; Rhodamine B; Visible light photocatalysis

Atomic force microscopy-based repeated machining theory for nanochannels on silicon oxide surfaces by Z.Q. Wang; N.D. Jiao; S. Tung; Z.L. Dong (pp. 3627-3631).

▶ We model AFM-based repeated nanomachining of nanochannels. ▶ The relationship between the final nanochannel depth and the initial nanochannel depth under a normal force is obtained numerically. ▶ Experiments show that the repeated nanomachining model is true. ▶ The resultant nanochannel is 22nm deep.The atomic force microscopy (AFM)-based repeated nanomachining of nanochannels on silicon oxide surfaces is investigated both theoretically and experimentally. The relationships of the initial nanochannel depth vs. final nanochannel depth at a normal force are systematically studied. Using the derived theory and simulation results, the final nanochannel depth can be predicted easily. Meanwhile, if a nanochannel with an expected depth needs to be machined, a right normal force can be selected simply and easily in order to decrease the wear of the AFM tip. The theoretical analysis and simulation results can be effectively used for AFM-based fabrication of nanochannels.

Keywords: Atomic force microscopy; Nanochannels; Nanoelectromechanical systems; Nanolithography; Nanotribology

The effect of different chemical compositions caused by the variation of deposition potential on properties of Ni–Co films by Ali Karpuz; Hakan Kockar; Mursel Alper (pp. 3632-3635).

▶ In the present work, the characterizations of Ni–Co films prepared at different potentials were performed and the results of investigation were reported. The magnetic and structural properties were observed to have a strong dependence on the Ni:Co ratio that was controlled by the deposition potential.The magnetic and microstructural properties of Ni–Co films electrodeposited at different cathode potentials were investigated. The compositional analysis revealed that the Ni content increases from 13at.% to 44at.% in the films with increasing deposition potential. Magnetic measurements showed that the saturation magnetization, M_s of the films decreased with increase of Ni content as the deposition potential increased. M_s values changed between 1160emu/cm³ and 841emu/cm³. The X-ray diffraction revealed that the crystalline structure of the films is a mixture of the predominant face-centered cubic (fcc) and hexagonal closed packed. However, the mixture phase turns to the fcc because of increasing Ni content up to 44at.% at the highest (−1.9V) potential by enhancing the intensity of reflections from the fcc phase. The changes observed in the magnetic and microstructural properties were ascribed to the changes observed in the chemical composition caused by the applied different deposition potentials.

Keywords: Electrodeposition; Ni–Co films; Deposition potential; Magnetic properties; Microstructure

Highly stable carbon-doped Cu films on barrierless Si by X.Y. Zhang; X.N. Li; L.F. Nie; J.P. Chu; Q. Wang; C.H. Lin; C. Dong (pp. 3636-3640).

▶ Cu–C films on silicon as barrierless Cu seed layer in ULSI. ▶ The Cu–C film achieves a low resistivity (2.7μΩ-cm). ▶ C is effective in inhibiting the detrimental Cu–Si interdiffusion. ▶ Good stability arises from enriched C in the interface layer and the fine Cu grains.Electrical resistivities and thermal stabilities of carbon-doped Cu films on silicon have been investigated. The films were prepared by magnetron sputtering using a Cu–C alloy target. After annealing at 400°C for 1h, the resistivity maintains a low level at 2.7μΩ-cm and no Cu–Si reaction is detected in the film by X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations. According to the secondary ion mass spectroscopy (SIMS) results, carbon is enriched near the interfacial region of Cu(C)/Si, and is considered responsible for the growth of an amorphous Cu(C)/Si interlayer that inhibits the Cu–Si inter-diffusion. Fine Cu grains, less than 100nm, were present in the Cu(C) films after long-term and high-temperature annealings. The effect of C shows a combination of forming a self-passivated interface barrier layer and maintaining a fine-grained structure of Cu. A low current leakage measured on this Cu(C) film also provides further evidence for the carbon-induced diffusion barrier interlayer performance.

Keywords: Cu interconnects; Carbon; Thin film; Metallization

SEM-EDX study of the crystal structure of the condensed combustion products of the aluminum nanopowder burned in air under the different pressures by E.M. Popenko; A.A. Gromov; Yu.I. Pautova; E.A. Chaplina; H.-J. Ritzhaupt-Kleissl (pp. 3641-3644).

▶ Combustion of Al nanopowder in air results in formation of the anisotropic crystals of AlN. ▶ The ratio ‘length/diameter’ is different for the crystals of AlN depending on air pressure during combustion. ▶ AlN formation during combustion is allowed by fast cooling of combustion products.The experimental results of combustion of aluminum nanopowder (ANP) in air and AlN crystals formation process were studied. The air pressure during the combustion process significantly affected the crystals growth mechanism. Crystals with the different morphology (whiskers, hexagonal crystals, rods) were found in the condensed combustion products.

Keywords: Aluminum; Nanopowder; Crystal structure; AlN; SEM-EDX

Substrate pre-treatment of flexible material for printed electronics with carbon nanotube based ink by Aurore Denneulin; Julien Bras; Anne Blayo; Charles Neuman (pp. 3645-3651).

▶ Innovative solution to make paper-based material suitable for printed electronics. ▶ Development of an UV-cured and inkjettable solution. ▶ Virgin and treated substrate characterization. ▶ Evaluation of the treatment with a carbon nanotube based inkjet ink.In this work, an innovative solution was developed in order to make paper-based material, used traditionally in the packaging and labelling industries, compatible with the printing of functional conductive inks. In order to avoid the deterioration of the ink functionalities due to different paper properties, a UV-curing inkjettable primer layer was developed. This pre-treatment enables homogeneous surface properties such as smoothness, absorption capacity and surface energy to be obtained, for almost all the examined substrates. To confirm the positive impact of such pre-treatment, conductivity has been measured when using a new conductive ink, combining the processability of the PEDOT–PSS conductive polymer with the high electrical properties of carbon nanotubes (CNTs). Significant improvement has been measured for all paper materials and similar conductivity (close to reference PET film) has been obtained whatever the substrate involved. This pre-treatment now makes it possible to consider paper-based material as a potential substrate for printed electronics. In this case, the substrate adaptation technique offers an innovative solution to produce low-cost and flexible electronics.

Keywords: Printed electronics; Inkjet printing; Flexible substrates; Papers; Primer layer; Conductive ink; Carbon nanotubes

Preparation and visible light photocatalytic activity of mesoporous N, S-codoped TiO₂(B) nanobelts by Qi Xiao; Linli Ouyang; Lan Gao; Chi Yao (pp. 3652-3656).

▶ The mesoporous N, S-codoped TiO₂(B) nanobelts are mesoporous structured and exhibit stronger absorption in the visible light region with red shift in the absorption edge. ▶ The photocatalytic activity of N, S-codoped mesoporous TiO₂(B) nanobelts increases with increasing the molar ratio of thiourea to Ti ( R). ▶ At R=3, the photocatalytic activity of the N, S-codoped TiO₂(B) sample TBLTS-3 reaches a maximum value. ▶ The high photocatalytic activity of N, S-codoped TiO₂(B) nanobelts can be attributed to the balance between strong absorption in visible light region and low recombination rate of electron/hole pairs.The mesoporous N, S-codoped TiO₂(B) nanobelts are synthesized via hydrothermal synthesis and post-treatment, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption–desorption measurements (BET), X-ray photoelectron spectra (XPS), and UV–vis diffuse reflectance spectra (DRS). The results show that the prepared samples are mesoporous structured and exhibit stronger absorption in the visible light region with red shift in the absorption edge. The photocatalytic activity of N, S-codoped mesoporous TiO₂(B) nanobelts is evaluated by the photocatalytic photodegradation of potassium ethyl xanthate (KEX) under visible light irradiation. It is found that the photocatalytic activity of the prepared samples increases with increasing the molar ratio of thiourea to Ti ( R). At R=3, the photocatalytic activity of the N, S-codoped TiO₂(B) sample TBLTS-3 reaches a maximum value. With further increasing R, the photocatalytic activity of the sample decreases. The high photocatalytic activity of N, S-codoped TiO₂(B) nanobelts can be attributed to the balance between strong absorption in visible light region and low recombination rate of electron/hole pairs.

Keywords: N, S-codoped TiO; ₂; (B) nanobelts; Mesoporous; Visible light; Photocatalytic activity

Hydrothermal synthesis of morphology-controllable Sb₂O₃ microstructures: Hollow spindle-like and cobblestone-like microstructures by Shengsong Ge; Qingyao Wang; Qian Shao; Yuhua Zhao; Xiaokun Yang; Xiaojie Wang (pp. 3657-3665).

Images in figure show the low- and high-magnification SEM images of hollow spindle-like and cobblestone-like Sb₂O₃ microstructures, respectively. Fig. a shows that the as-prepared product exists a great deal of uniform broken spindle-like structures in high yield, which confirms the formation of hollow structures. Fig. b shows HRSEM images of the amplified morphology of the pore about 300nm in diameter and the surface of the sample is very rough, indicating that the microspindle is composed of many smaller homogeneous nanoparticles. Fig. c and d show that the cobblestone-like microstructure is in diameter of about 3μm and the surface of an individual cobblestone-like Sb₂O₃ particle is not very smooth, covered with uneven salience.Display Omitted▶ We report the fabrication of novel uniform hollow spindle-shaped and cobblestone-shaped microarchitectures by using CTAB as a soft-template in mixed solvents via a facile hydrothermal synthetic method. ▶ We have varied different reaction parameters such as the reaction temperature and time to study their effect on the size and shape of the formed Sb₂O₃ morphology. ▶ The possible mechanisms leading to spindle-shaped and cobblestone-shaped microarchitectures were proposed, respectively. ▶ In addition, variations of the crystal structure and morphology of the samples were systematically investigated using XRD, SEM, TEM, BET and micro-Raman spectroscopy.Hollow spindle-like and cobblestone-like Sb₂O₃ microstructures, have been successfully synthesized via a hydrothermal method by using cetyltrimethylammonium bromide (CTAB) as soft-templates. Results from XRD, SEM, TEM, Raman and BET showed that experimental parameters, such as the reaction temperature and time, played crucial roles in the respective morphological control of Sb₂O₃ microstructures. On the basis of these results, possible growth mechanisms for the formation of hollow spindle-like and cobblestone-like microstructures are presented and discussed.

Keywords: Nanostructures; Hydrothermal crystal growth; Growth mechanism

Dependence of microstructure and magnetic properties of FePt/B nanocomposite films on boron content by Y.L. Li; T.F. Feng; Z.Y. Chen (pp. 3666-3669).

▶ FePt/B nanocomposite films with tunable magnetic properties have been fabricated. ▶ Boron atoms are found enlarging FePt lattices through interstitial incorporation. ▶ Intergranular segregation of boron atoms results smaller FePt grains.Compared with previous work, FePt/B nanocomposite films with larger B content in a wide range were prepared by magnetron sputtering plus subsequent annealing on Si (100) substrates. When the volume percentage is no less than 12%, both interstitial incorporation and intergranular segregation of the B are found, resulting an enlargement of the FePt lattice and a decrease of the FePt grain size. Effect of B content on magnetic properties, such as magnetization, switching field and exchange coupling of the FePt based films, is also discussed.

Keywords: Magnetron sputtering; Vacuum annealing; Nanocomposite film; Magnetic recording

Structural and optoelectronic properties of vacuum evaporated SnS thin films annealed in argon ambient by Biswajit Ghosh; Rupanjali Bhattacharjee; Pushan Banerjee; Subrata Das (pp. 3670-3676).

▶ Characterization of SnS films as a function of temperature and duration of annealing. ▶ No noticeable structural change for annealing upto 300° in argon ambient. ▶ Segregation of tin phase observed for SnS films annealed at 400°C for 2h. ▶ Variation of photosensitivity of SnS films with annealing parameters was studied.In this work, 650nm polycrystalline SnS thin films were grown by thermal evaporation of high purity tin sulfide powder at 250°C substrate temperature, followed by post deposition annealing at 200°C and 300°C for 2, 4 and 6h, and at 400°C for 2 and 4h in argon ambient. The XRD pattern of the as-deposited and annealed SnS films led to the conclusion that the as-deposited films were polycrystalline in nature with preferentially oriented along (111) direction. The direct bandgap of all the films was found to be observed between 1.33 and 1.53eV. Except for annealing at 400°C all the films were nearly stoichiometric in nature, suggesting lower rate of desulfurization at that ambient. However, higher annealing temperature has resulted in the segregation of tin phase. All the films showed good absorption in the visible range. The as-deposited and annealed films showed p-type conductivity. Hall measurement revealed the carrier concentration and mobility ranging from 10¹⁵ to 10¹⁶cm⁻³ and 0.8 to 31.6cm²V⁻¹s⁻¹ respectively. The photoconductivity measurements of all the SnS films were carried out by recording the lowering of resistance of the respective films with time under illumination.

Keywords: SnS; Evaporation; X-ray difraction; FESEM; Photoresponse

The research on mechanical effect etching Si in pulsed laser micromaching under water by Long Yuhong; Xiong Liangcai; Shi Tielin (pp. 3677-3681).

▶ The removal mechanism of brittle material etched by mechanical effects was discussed. ▶ The approximate mechanics model of indentation fracture was used to analyze removal mechanism. ▶ A theoretical model for material removal rate of brittle materials was proposed. ▶ The experiment of laser machining underwater was adopted to validate the model.To explore further the influencing of mechanical effects on laser machining in the liquid, in the process of great-energy and short-pulsed laser irradiating matter in the liquid, the experiments of 248nm laser etching n-Si under water were carried out. The removal mechanism of brittle material etched by mechanical effects, which is induced during high-energy and short-pulsed laser machining in the liquid, was discussed. In the paper, the approximate mechanics model of indentation fracture was used to analyze the mechanical effects for removing brittle materials of silicon when laser machining in the liquid. Based on this, a theoretical model of material removal rate was proposed; the experiment of laser machining under water was adopted to validate the model. The experimental results indicate that the removal rate of brittle material caused by shock forces is relatively great.

Keywords: Laser technique; Mechanical effect; Laser; Etching; Silicon

Formation of alumina–ceria mixed oxide in model systems by Tomáš Skála; Nataliya Tsud; Kevin C. Prince; Vladimír Matolín (pp. 3682-3687).

▶ Interaction of Ce with Al in mixed oxide model studies was studied. ▶ The interaction was strong and cerium aluminate was formed. ▶ The maximum thickness of cerium aluminate was limited by diffusion.Interaction of aluminium with cerium oxide was studied by photoelectron spectroscopy of Al/CeO₂(111) and CeO₂/Al(111) model systems. It was found in both cases that metallic aluminium was immediately oxidized, CeO₂ was partially reduced and a mixed oxide with cerium present as Ce³⁺ was formed. The compound is probably cerium aluminate CeAlO₃ mixed with Al₂O₃ or Ce₂O₃. In both cases the intermixing was limited by the diffusion of aluminium into ceria. The excess of deposited material above this limit formed AlO_x and CeO₂ overlayers on the top of the mixed oxide+aluminate/CeO₂ and mixed oxide+aluminate/Al films, respectively.

Keywords: PACS; 68.47.Gh, 79.60.Dp, 73.61.Le, 81.05.JeCerium oxide; Aluminium oxide; Cerium aluminate; Thin layer growth; Photoelectron spectroscopy

Preparation and characterization of iodine-doped mesoporous TiO₂ by hydrothermal method by Wang Wei-an; Shi Qian; Wang Yu-ping; Cao Jin-li; Liu Guo-qing; Peng Pan-ying (pp. 3688-3696).

▶ Iodine-doped mesoporous TiO₂ (I/TiO₂) was prepared by hydrothermal method potassium iodate as iodine sources. ▶ Iodine-doped TiO₂ calcinated at 300°C has good anatase crystal and large BET specific surface area. ▶ The iodine in I/TiO₂ mainly exists in the form of I₂ and makes catalysts photosensitize. ▶ I/TiO₂ can produceOH after dysprosium thallium halogen lamp irradiation.Iodine-doped mesoporous TiO₂ (I/TiO₂) was prepared by hydrothermal method, using tetrabutyl titanate as precursor, potassium iodate as iodine sources. The as-prepared I/TiO₂ catalysts were characterized by UV–vis, XRD, TEM, BET, TG/DTA, XPS and photoluminescence (PL) spectroscopy. Production ofOH radicals on the I/TiO₂ surface was detected by the PL technique using terephthalic acid as a probe molecule. The effects of hydrothermal reaction temperature, calcination temperature and iodine doping content on the structure and properties of the catalysts were investigated. The results showed that iodine-doped TiO₂ calcinated at 300°C have good anatase crystal. The optimal hydrothermal conditions have been determined to be that reaction temperature 120°C, calcinated temperature 300°C and added 1.16mmol iodine dopants. The average particle size of I/TiO₂ synthesized under optimal condition (I-3 sample) is about 3.9nm. The I-3 photocatalyst contains 100% anatase crystalline phase of TiO₂. BET specific surface area of I-3 sample is184.8m²g⁻¹ and is 3.67 times that of pure TiO₂ (50.37m²g⁻¹). Iodine in I/TiO₂ catalyst mainly exists in the form of I₂, and photoactivity of I/TiO₂ catalyst in visible light comes from photosensitize of I₂. I/TiO₂ catalysis shows very high efficiency for the degradation of phenol under visible light.

Keywords: Iodine doped TiO; ₂; Hydrothermal method; KIO; ₃; Visible light; Photocatalysis

Comparison of photocatalytic performance of anatase TiO₂ prepared by low and high temperature route by Changyuan Hu; Shuwang Duo; Tingzhi Liu; Junhuai Xiang; Mingsheng Li (pp. 3697-3701).

▶ Anatase TiO₂ was prepared by low temperature (TiO₂-120) and high temperature route (TiO₂-500). ▶ Low temperature synthesis of anatase TiO₂ is advantageous for energy saving. ▶ TiO₂-120 showed more advantages in small particle and strong photoluminescence over TiO₂-500. ▶ TiO₂-120 showed higher photo-degradation activity of methyl orange than TiO₂-500.Anatase TiO₂ was prepared by a facile sol–gel method at low temperature through tailoring the pH of sol–gel without calcination. As a control, anatase TiO₂ was also synthesized by the conventional sol–gel process, in which calcination at 500°C was required to transform the amorphous oxide into highly crystalline anatase. As-prepared samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). Their photocatalytic activities were evaluated by degradation of methyl orange under UV light irradiation. On the basis of experiment results, it could be concluded that TiO₂ prepared by low temperature route showed more advantages in small particle size, highly dispersion nature, abundance of surface hydroxyl groups, strong PL signal, and high photocatalytic activity over TiO₂ obtained by the conventional sol–gel process. Furthermore, the reason of the former possessing higher photocatalytic activity was discussed.

Keywords: TiO; ₂; Semiconductor; Sol–gel method; Photocatalytic degradation; Methyl orange

Synthesis and characterization of poly(N-methylpyrrole)/TiO₂ composites on steel by M.R. Mahmoudian; W.J. Basirun; Y. Alias (pp. 3702-3708).

▶ The synthesis of PMPy in the presence of TiO₂ NPs increases the area of polymer. ▶ The increase of area of synthesized PMPy can increase its performance. ▶ Synthesized PMPy in the presence of TiO₂ NPs increases the R_po of the coating.Poly(N-methyl pyrrole) coating was successfully electrodeposited on steel substrates in mixed electrolytes of dodecyl benzene sulphonic acid (DBSA) with oxalic acid in the absence and the presence of TiO₂ nanoparticles (NPs). The morphology and compositions were characterized by Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), Energy-Dispersive X-ray spectroscopy (EDX). X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to calculate the size of nanoparticles. Electrode/polymer/electrolyte system was studied by Electrochemical Impedance Spectroscopy (EIS). The FESEM micrographs suggest that the incorporation of TiO₂ nanoparticles affects the morphology of the film significantly and makes the TiO₂ to be loosely piled up with PMPy. The results of EIS showed that synthesized PMPy in the presence of TiO₂ NPs increases and decreases the R_po and C_c of the coating respectively. The increase of the area of synthesized PMPy in the presence of nanoparticles can increase its ability to interact with the ions liberated during the corrosion reaction of steel in NaCl solution.

Keywords: Poly(N-methyl pyrrole); Electropolymerization; TiO; ₂; (NPs); Pore resistance; Coating capacitance

Evaluation of the surface properties of PTFE foam coating filter media using XPS and contact angle measurements by Byung Hyun Park; Myong-Hwa Lee; Sang Bum Kim; Young Min Jo (pp. 3709-3716).

▶ The PTFE foam coating filter demonstrates an excellent hydrophobic and good oleophobic properties at the same time. ▶ The contact angle of liquid droplets on the filter surface was used to predict the potential wetability of the filter against water or oil. ▶ In addition, very low surface free energy of the filter medium, which was evaluated using the Owens–Wendt method, resulted in a very stable surface and high de-dusting quality.A newly developed PTFE foam coating filter was developed which can be used for hot gas cleaning at temperatures up to 250°C. The emulsion-type PTFE was coated onto a woven glass fiber using a foam coating method. The filter surface was closely examined using X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The XPS results were used to determine the binding force between the carbon and fluorine of PTFE, which imparts coating stability to the filter medium. More than 95% of the bonds of the PTFE foam coating filter were between carbon and fluorine, and this filter demonstrated excellent hydrophobic and good oleophobic properties at the same time. The contact angles of liquid droplets on the filter surface were used to predict the potential wetability of the filter against water or oil. In addition, the very low surface free energy of the filter medium, which was evaluated using the Owens–Wendt method, demonstrates a very stable surface and a high de-dusting quality.

Keywords: Porous filter media; PTFE foam coating; De-dusting; Contact angle; Bag filter

Synthesis of amorphous carbon nanowalls by DC-PECVD on different substrates and study of its field emission properties by D. Banerjee; S. Mukherjee; K.K. Chattopadhyay (pp. 3717-3722).

▶ Amorphous carbon quasi vertical nanowalls have been synthesized via DC-PECVD on both copper and silicon substrates. ▶ The morphology of the as-prepared samples has been investigated with the help of FESEM and AFM. ▶ The as-prepared carbon nanowalls showed good field electron emission. ▶ The effect of inter-electrode distance on the field electron emission has also been studied in detail.Amorphous carbon thin films with quasi vertical nanowall-like morphologies have been synthesized via direct current plasma enhanced chemical vapor deposition on both copper and silicon substrates with acetylene as a carbon precursor. The deposition temperature and pressure were maintained at 750°C and 5mbar respectively. The morphology of the as-prepared samples has been investigated with the help of a field emission scanning electron microscope and an atomic force microscope, both revealing nanowall-like morphologies with thicknesses of the walls ∼6–15nm. The as-prepared carbon nanowalls showed good field electron emission with a turn-on field as low as 1.39V/μm. The effect of inter-electrode distance on the field electron emission has also been studied in detail.

Keywords: Carbon nanowall; PECVD; FESEM; Field emission

Wetting process of electrolyte in high density Cu/Sn micro-bumps electrodepositing by Jinglin Bi; Huiqin Ling; Anmin Hu; Tao Hang; Ming Li (pp. 3723-3727).

▶ High density Cu/Sn micro-bumps electrodepositing. ▶ Electrolyte is hard to reach up to the bottom of micro-hole. ▶ Under mechanical action, void free micro-bumps was achieved with depth of 60μm and radius of 30μm. ▶ A model shows wetting process of electrolyte.Wetting process of electrolyte in high density Cu/Sn micro-bumps electrodepositing is reported in this paper. Three methods were adopted to enable electrolyte to permeate photo-etching micro-holes with high aspect ratio, including plasma treatment, adding wetting additive in electrolyte and mechanical action. Wettability of the samples with electrolyte was improved by the first two methods, according to contact angle and surface tension measurement. However, electrolyte still cannot reach up to the bottom of micro-hole. And then, electrolyte was subjected to mechanical action, including agitation and ultrasonic vibration. Under mechanical action, void free Cu/Sn micro-bumps fabrication was achieved in photo-etching micro-holes with depth of 60μm and radius of 30μm. At last, we proposed a model to show wetting process of electrolyte in photo-etching micro-holes.

Keywords: Wetting process; Void free Cu/Sn micro-bumps; Electrodepositing method

Gd³⁺, N-codoped trititanate nanotubes: Preparation, characterization and photocatalytic activity by Haijin Liu; Guoguang Liu; Guohong Xie; Minli Zhang; Zehua Hou; Zhanwei He (pp. 3728-3732).

▶ Gd³⁺, N-codoped trititanate nanotubes have been prepared by hydrothermal and ion-exchanging method. ▶ Synergistic reaction occurs between Gd³⁺ and N co-doping. ▶ The photocatalytic activity of TiO₂ has been enhanced significantly under visible light irradiation after Gd³⁺, N-codoping.Trititanate nanotubes were prepared using hydrothermal method and then co-doped with Gd³⁺ and N through ion-exchanging with H⁺. They were characterized by X-ray photoelectron spectra (XPS), high-resolution transmission electronmicroscopy (HRTEM), X-ray diffraction (XRD), UV–vis diffusion reflection spectra (UV–vis DRS) and photoluminescence (PL) spectra. The photocatalytic activities were investigated with Rhodamine B as the model pollutant. The results indicated that synergistic reaction occurred when codoping with Gd³⁺ and N and the photocatalytic activities of TiO₂ were enhanced significantly under visible light irradiation.

Keywords: Trititanate nanotube; Co-doping; Photocatalysis; Ion-exchange; Gadolinium; Nitrogen

Crystallization and annealing effects of sputtered tin alloy films on electromagnetic interference shielding by Fei-Shuo Hung; Fei-Yi Hung; Che-Ming Chiang (pp. 3733-3738).

▶ Sn, Al and Cu possess EMI shield efficiency and can be used to make Sn based alloying thin films for EMI applications. ▶ Sn alloying film must be an advanced method for EMI shielding. ▶ Due to the large number of IMCs and lower content of β-Sn, the higher frequency EMI shielding of the annealed Sn–Cu thin films deteriorated. ▶ The Sn–Al films had rich-Sn phases and rich Al phases in the matrix which were able to promote the EMI shielding.Sn, Al and Cu not only possess electromagnetic interference (EMI) shield efficiency, but also have acceptable costs. In this study, sputtered Sn–Al thin films and Sn–Cu thin films were used to investigate the effect of the crystallization mechanism and film thickness on the electromagnetic interference (EMI) characteristics. The results show that Sn– xAl film increased the electromagnetic interference (EMI) shielding after annealing. For as-sputtered Sn– xCu films with higher Cu atomic concentration, the low frequency EMI shielding could not be improved. After annealing, the Sn–Cu thin film with lower Cu content possessed excellent EMI shielding at lower frequencies, but had an inverse tendency at higher frequencies. For both the Sn– xAl and Sn– xCu thin films after crystallization treatment, the sputtered films had higher electrical conductivity, however the EMI shielding was not enhanced significantly.

Keywords: Electromagnetic interference (EMI); Sn–Al; Sn–Cu

Thermal study and structural characterization of self-assembled monolayers generated from diadamantane disulfide on Au(111) by Waleed Azzam; Asif Bashir; Osama Shekhah (pp. 3739-3747).

Display Omitted▶ Preparation and characterization of self-assembled monolayer, nanotechnology, and STM.Self-assembled monolayers (SAMs) formed from diadamantane disulfide (DADS) on Au(111) have been characterized using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and infrared reflection absorption spectroscopy (IRRAS). SAMs of DADS prepared at room temperature (RT) were found to form at least four different orientational ordered domains having densely packed and well-ordered structure with nearest neighbour distance of 7.0±0.3Å. The spectroscopic techniques used in this work reveal the formation of highly oriented SAMs with molecular axis orientated perpendicular to the surface. Annealing the SAMs prepared at RT to temperatures below 353K results in no structural changes from that observed at RT. The samples that annealed at temperatures higher than 353K exhibited different surface morphologies and structural changes were observed for these SAMs. In addition, the number of the different rotational domains is reduced to three after this annealing. After annealing at 353–393K, the domain boundaries that were missed in SAMs prepared at RT or after annealing at temperature lower than 353K appear in a shape similar to those observed for n-alkanethiols on Au(111). Moreover, the SAMs show a highly ordered hexagonal close-packed molecular lattice with a measured nearest neighbour distance of 7.6±0.1Å, corresponding to a(7×7)R19.12° unit cell.

Keywords: SAM; Adamantanethiol; STM; FTIR; XPS; Thermal

Orthogonal optimization for room temperature magnetron sputtering of ZnO:Al films for all-solid electrochromic devices by Tao Wang; Xungang Diao; Peng Ding (pp. 3748-3752).

▶ ZnO:Al (ZAO) films were investigated and optimized through Orthogonal Array Method. ▶ Reliance of film quality on four control factors were investigated simultaneously. ▶ Impact sensitivity of factors and parameters to deposit quality films were obtained. ▶ Optimized ZAO films were successfully applied in an all solid electrochromic device.In order to obtain competent and quality (high transparency, conductivity and stability) aluminium-doped zinc oxide (ZnO:Al, ZAO) films for all solid electrochromic devices, ZAO films were prepared by direct current (D.C.) reactive magnetron sputtering at room temperature based on orthogonal design. Optical and electrical property dependences of the films on the four dominant sputtering parameters: sputtering time, target–substrate distance, sputtering power and O₂ flow ratio were simultaneously investigated with measured results using mathematical and statistical method. Optimal Parameters to fabricate ZAO films with optimum comprehensive performances were obtained ultimately. Resistivity and carrier concentration of ZAO film deposited with optimized parameters were 3.89×10⁻⁴Ωcm and 1.09×10²¹cm⁻³, respectively. ZAO films with these superior properties were employed as transparent electrodes eventually in a WO₃ based all-solid electrochromic device which displayed good electrochromic performance. The regulation range for transmittance in the visible region of the device was more than 50%, which was comparable to that of the device adopting indium tin oxide (ITO) films as electrodes.

Keywords: ZAO films; Orthogonal design; Magnetron sputtering; Electrochromic device

Plasma/thermal-driven the rapid wettability transition on a copper surface by Xiaotao Zhu; Zhaozhu Zhang; Xuehu Men; Jin Yang; Xianghui Xu; Xiaoyan Zhou (pp. 3753-3757).

▶ A superhydrophobic surface was fabricated on the copper substrate by a simple solution–immersion process followed by stearic acid modification. ▶ Reversible wettability transition was realized by the alternation of plasma treatment and annealing process. ▶ It just took 21min to fulfill the whole wetting transition.A simple and time-saving method to realize the reversible wettability transition is reported. Through a solution–immersion process followed by stearic acid modification, a superhydrophobic surface was prepared on the copper surface. After being treated by air-plasma exposure, the surface wettability was converted into superhydrophilicity. XPS analysis demonstrated that the incorporation of oxygen species by air-plasma activation accounted for the highly hydrophilic character of the surface. Upon annealing the plasma-treated surface in air, the non-oxidized alkyl chains were transferred to the surface for recovery the superhydrophobicity. It was found that the recovery was fast upon annealing at a relative high temperature. By the alternation of air-plasma treatment and annealing process, the rapid reversible wettability transition between superhydrophobic and superhydrophilic state was realized. The shortest processing time for a whole reversible wettability transition was 21min.

Keywords: Superhydrophobic surface; Plasma treatment; Wettability transition; Copper

On the resonant SHG response of ultra-thin alkali (K, Rb)-covered Si(111)-7×7 by Kenichi Fujiwara; Youichi Karaki; Daisuke Inoue; Masatoshi Tanaka; Takanori Suzuki (pp. 3758-3762).

▶ Alkali metals adsorbed on Si(111)-7×7 show a typical SHG resonance enhancement. ▶ Wavelength dependent SHG peak was observed around 0.4 monolayer at 1.17eV. ▶ Previous proposals of bond-counting interpretation have been questioned. ▶ Resonance due to transition between alkali-derived electronic states is suggested. ▶ Phase measurement of SH fields identified multiple different origins for SHG.Room temperature adsorption of K either on Si(111)-7×7 or on dielectric SiO₂-covered Si(111) followed by second-harmonic generation (SHG) observation clearly identified a characteristic resonance enhancement typical to Si(111)-7×7. The polarization selected SHG as a function of coverage obtained at different photon energies between 1.17-eV and 1.55-eV show a similar variation of the SH intensity both for K and Rb adsorption on Si(111)-7×7. For submonolayer coverage, wavelength dependent SHG peak observed around 0.4 monolayer (ML) was followed by an SHG peak around 0.9 ML that was less dependent on the wavelength. Previous proposals for an interpretation of the former peak have been questioned. Instead, the former peak has been suggested as being a resonant enhancement due to the transition between alkali atomic-derived electronic states, while the origin of the latter peak remains unidentified. Multiple SHGs of different origins are identified through a phase measurement of SH fields.

Keywords: Alkali metals; Second-harmonic generation; Silicon; Laser; Adsorption; Submonolayer

Surface modification of coir fibre involving oxidation of lignins followed by reaction with furfuryl alcohol: Characterization and stability by Sudhir Kumar Saw; Gautam Sarkhel; Arup Choudhury (pp. 3763-3769).

▶ Attempt to develop a new fibre surface modification involving formation of quinines followed by reaction with furfuryl alcohol. ▶ Effect of surface modification on morphological structure, contact angle and surface energy of the coir fibres are presented. ▶ Surface modification with furfuryl alcohol leads the significant enhancement in mechanical properties and moisture resistance capability.In this study, the chemical treatment of the coir fibres was executed through oxidation with aqueous ClO₂ followed by grafting with furfuryl alcohol (FA), leading to create a coating around the fibres more compatible with the polymeric matrices. The ClO₂ was used to oxidize mainly phenolic syringyl and guaiacyl units of the lignin polymer to create quinones, which were characterized by UV–vis spectroscopy and Fourier transform infrared spectroscopy. In addition, the surface features of modified fibres were studied using scanning electron microscopy. The extent of FA-grafting was found higher (weight gain 17.7%) for oxidized fibre compared to those for non-oxidized fibre (weight gain 2.2%). The surface modification with FA-grafting reduced the hydrophilicity of the coir fibre, as confirm by the dynamic contact angle and water absorption measurements. The thermal and mechanical properties of untreated, oxidized and FA-grafted coir fibres were evaluated and compared.

Keywords: Coir (; Cocos nucifera; ) fibre; Surface modification; Morphology; Surface energy; Mechanical and thermal properties; Water absorption

Characteristics of PVD-CrAlSiN films after post-coat heat treatments in nitrogen atmosphere by Wei-Yu Ho; Cheng-Hsun Hsu; Chi-Wei Chen; Da-Yung Wang (pp. 3770-3775).

▶ We first have deposited PVD-CrAlSiN films, and then post-annealed the films with different temperatures. ▶ Characteristics of the annealed films were analyzed for obtaining an optimal heating condition. ▶ The film heated at 600°C could provide the prime mechanical properties, such as higher hardness and better wear resistance.In this study, the CrAlSiN films were first synthesized using the cathodic arc evaporation system with Cr (99.99at.%) metal and Al₈₈Si₁₂ alloy dual cathodes. The films then underwent heat treatments at different temperatures of 400, 600, and 800°C for 3h in a nitrogen atmosphere. Microstructures of the heat-treated films were analyzed with X-ray photoelectron spectroscopy, X-ray diffractometer, and scanning electron microscopy. The mechanical properties of the films were explored via the Rockwell indentation test, the nano-indentation test, the ball-on-disc tribological test, and the cutting test. The results show that the CrAlSiN film heat-treated at 600°C has the highest hardness, lowest friction coefficient, and the best wear resistance among the tested films (with or without heat-treatments). Moreover, the film, after being heated at 600°C, could provide an optimal machining performance for the cutting test.

Keywords: CrAlSiN; Heat treatment; Tribological test; Cutting test

The properties of plasma-enhanced atomic layer deposition (ALD) ZnO thin films and comparison with thermal ALD by Doyoung Kim; Hyemin Kang; Jae-Min Kim; Hyungjun Kim (pp. 3776-3779).

▶ TH and PE-ALD ZnO films were evaluated comparatively. ▶ The resistivity of PE-ALD ZnO is higher than it of TH-ALD ZnO. ▶ In low temperature PE-ALD, impurity due to oxygen interstitial was detected. ▶ ZnO TFT performances were strongly dependent on the growth technique.Zinc oxide (ZnO) thin films were prepared by plasma-enhanced atomic layer deposition (PE-ALD) using oxygen plasma as a reactant and the properties were compared with those of thermal atomic layer deposition (TH-ALD) ZnO thin films. While hexagonal wurzite phase with preferential (002) orientation was obtained for both cases, significant differences were observed in various aspects of film properties including resistivity values between these two techniques. Photoluminescence (PL) measurements have shown that high resistivity of PE-ALD ZnO thin films is due to the oxygen interstitials at low growth temperature of 200°C, whose amount decreases with increasing growth temperature. Thin film transistors (TFT) using TH- and PE-ALD ZnO as an active layer were also fabricated and the device properties were evaluated comparatively.

Keywords: ZnO; ALD; Thermal; Plasma-enhanced; Thin film transistor

Superhydrophilicity and photocatalytic enhancement of titania nano thin films by M. Kazemi; M.R. Mohammadizadeh (pp. 3780-3785).

▶ The influences of three different aging times on crystallinity, photocatalytic, and superhydrophilicity behaviors of the anatase TiO₂ thin films were investigated. ▶ In one of the samples, photocatalytic and superhydrophilic phenomena reach optimum, simultaneously. ▶ This is very useful for self-cleaning application.Anatase TiO₂ thin films were prepared on glass substrates by the sol–gel dip coating method with TiCl₄ as the Ti precursor and Tween 80 as a surfactant. XRD, AFM, and UV–Vis photospectroscopy experiments were used to analyze the structural and optical characteristics of the films. The influences of three different aging times on crystallinity, morphology, photocatalytic, superhydrophilicity behaviors, and size of the obtained TiO₂ grains were investigated. With increasing the aging time, crystallite size of anatase structure and thickness of the films were increased. It was shown that in one of the samples, photocatalytic and superhydrophilic phenomena reach optimum, simultaneously. This could be very useful for self-cleaning application.

Keywords: PACS; 68.08.Bc; 82.65.+r; 82.30.RsSol–gel; TiO; ₂; thin films; Aging time; Tween 80; Photocatalytic; Superhydrophilicity

Effects of surface roughness and energy on ice adhesion strength by M. Zou; S. Beckford; R. Wei; C. Ellis; G. Hatton; M.A. Miller (pp. 3786-3792).

▶ Ice adhesion strength correlates with water contact angle at similar roughness. ▶ Ice adhesion strengths on rougher surface are larger than on smoother surfaces. ▶ Higher water contact angle is not necessarily good for ice adhesion reduction.The aim of this study is to investigate the effects of surface roughness and surface energy on ice adhesion strength. Sandblasting technique was used to prepare samples with high roughness. Silicon-doped hydrocarbon and fluorinated-carbon thin films were employed to alter the surface energy of the samples. Silicon-doped hydrocarbon films were deposited by plasma-enhanced chemical vapor deposition, while fluorinated-carbon films were produced using deep reactive ion etching equipment by only activating the passivation step. Surface topographies were characterized using scanning electron microscopy and a stylus profilometer. The surface wetting properties were characterized by a video-based contact angle measurement system. The adhesion strength of ice formed from a water droplet on these surfaces was studied using a custom-built shear force test apparatus. It was found that the ice adhesion strength is correlated to the water contact angles of the samples only for surfaces with similar roughness: the ice adhesion strength decreases with the increase in water contact angle. The study also shows that smoother as-received sample surfaces have lower ice adhesion strength than the much rougher sandblasted surfaces.

Keywords: Ice adhesion strength; Surface roughness; Water contact angle; Aluminum; Sandblasting; Hydrophobic

Novel Pt nanowires modified screen-printed gold electrode by electrodeposited method by Hongli Zhao; Changxiang Zhou; Yuanjie Teng; Chen Chen; Minbo Lan (pp. 3793-3797).

▶ The Pt nanowires were fabricated on the SPGE by template strategy. ▶ The mesoporous template was prepared by the EASA method on the SPGE. ▶ Pt NWs were electrodeposited in the meosoporous channel on the Au electrode. ▶ The diameter of each Pt NWs could reach about 3.2nm. ▶ The SPGE could be mass produced conveniently and cost low.In this work, the preparation and characterization of novel Pt nanowires (Pt NWs) on the screen-printed gold electrode (SPGE) surface are reported. Firstly the mesoporous template was prepared by the electro-assisted self-assembly (EASA) method on the manual SPGE. Then, in the potentiostatic condition, Pt NWs were electrodeposited in the meosoporous channel on the Au electrode surface using the chronopotentiometry (CP) method at room temperature. The synthesized Pt NWs were characterized by cyclic voltammetry (CV), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) spectrometer. The results indicated that Pt NWs were successfully electrodeposited on the SPGE substrate, even the diameter of each Pt NWs could reach 3.2nm. Furthermore, the SPGE could be mass produced conveniently and cost low which had very promising application prospect. And it is significant that the Pt NWs modified SPGE could function as an electrode in an electrochemical biosensor.

Keywords: Pt nanowires; Screen-printed gold electrode; Mesoporous template; Electrodeposit

Photodegradation of rhodamine B and methyl orange over one-dimensional TiO₂ catalysts under simulated solar irradiation by Changsheng Guo; Jian Xu; Yan He; Yuan Zhang; Yuqiu Wang (pp. 3798-3803).

▶ Two 1D TiO₂ nanostructures were synthesized by the hydrothermal method. ▶ The catalysts exhibited better photocatalytic activities than commercial P25 TiO₂. ▶ The catalysts showed good stabilities in cycle test for photocatalytic degradation.In this paper, two one-dimensional (1D) TiO₂ nanostructures, nanotube and nanowire were synthesized by a hydrothermal method using Degussa P25 TiO₂ as a precursor. The synthesized anatase TiO₂ nanotubes with the diameters of 10–20nm and length of several hundred nanometers were formed from P25 and NaOH with the hydrothermal treatment temperature at 150°C, and anatase TiO₂ nanowires with the diameters of 10–40nm and length up to several micrometers were prepared at 180°C. The photocatalytic activity of the two nanostructures was evaluated by degrading rhodamine B (RhB) and methyl orange (MO) in aqueous solutions under simulated solar light irradiation. The results suggested that the TiO₂ nanocatalysts displayed higher degradation activity compared to P25. For RhB, 98.9% and 91.9% of RhB were removed by nanotubes and nanowires, respectively after 60min irradiation in comparison to the 81.8% removal by P25. Similar trend was observed for MO, with the removal percentage of 95.6%, 88.3% and 74.9%, respectively by TiO₂ nanotubes, nanowires and P25. Meanwhile, RhB and MO showed different photodegradation rates in nanotubes and nanowires suspensions, probably due to the morphology and crystal structure of the TiO₂ nanocatalysts which play important roles in the degradation activity of the catalysts.

Keywords: One-dimensional nanostructures; Titanium dioxide; Photocatalysis; Rhodamine B; Methyl orange

The preparation and corrosion behaviors of MAO coating on AZ91D with rare earth conversion precursor film by Jingshun Cai; Fahe Cao; Linrong Chang; Junjun Zheng; Jianqing Zhang; Chunan Cao (pp. 3804-3811).

▶ MAO coating on AZ91D with rare earth conversion precursor film. ▶ Lower porosity, thicker coating and higher corrosion resistance. ▶ Microstructure and composition characterization of MAO coating. ▶ A model with two layer film for corrosion process.A novel kind of micro-arc oxidation (MAO) coating was prepared on magnesium alloy surface coated with rare earth conversion film (RE-film) in an alkaline aluminum oxidation electrolyte by AC power source. Inspection of scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) microspectroscopy, the structure and composition of MAO coating formed on AZ91D with RE-film under different applied voltages were investigated and the performance of the optimized MAO coating compared with the MAO coating directly formed on magnesium alloy. As the pretreatment of magnesium alloy with RE-film, the cerium oxides can be incorporated into the MAO coatings, reduce porosity of the MAO coating surface and enhance the thickness of MAO coating. These structure features and the cerium oxides incorporated into the MAO coating result in greatly improved corrosion resistance. Base on electrochemistry impedance spectroscopy (EIS) measurement, the electronic structure and composition analysis of the MAO coating, a double-layer structure, with a compact inner layer and a porous outer layer, of the coating was proposed for understanding its corrosion process.

Keywords: Magnesium alloy; Rare earth conversion film; Micro-arc oxidation; Porosity

Dopant based electron beam lithography in Cu_xTiSe₂ by T.E. Kidd; D. Klein; T.A. Rash; L.H. Strauss (pp. 3812-3816).

▶ We have developed a dopant based e-beam lithography technique. ▶ Iodine vapor draws copper ions out of a copper doped TiSe₂ crystal. ▶ Copper and iodine react to form sub-micron CuI crystallites on the surface. ▶Size and shape of crystallites controlled by temperature and e-beam exposure. ▶ E-beam exposure inhibits diffusion through surface to enable patterning of CuI.A method for creating a patterned array of sub-micron crystals on the surface of a doped layered dichalcogenide using a scanning electron microscope has been developed. Exposing the surface of copper doped TiSe₂ to iodine vapor induces sub-micron CuI crystals to form upon the surface. The copper ions diffuse to the surface from within the crystal to react with the iodine vapor, with larger crystals forming at higher temperatures. The amount and size of the crystals formed in a given area could be controlled by first exposing of portions of the surface to electron radiation within the microscope. Increasing the radiation exposure results in the formation of fewer and smaller CuI crystallites, and it is possible to completely prevent their formation using large exposures. It appears that the electron beam creates a thin barrier that limits the diffusion of copper ions to the surface. The system is sufficiently inert that exposing the surface to air for a few hours has no significant effect. The resultant surface features can be arranged with a lateral resolution limited mainly by the size of the features themselves.

Keywords: Dichalcogenide; Intercalation; Doping; Electron beam lithography; Diffusion; TiSe; ₂

Sections

Personal tools

Applied Surface Science (v.257, #8)

Sections

Personal tools

Local resources

Applied Surface Science (v.257, #8)