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Applied Surface Science (v.257, #22)

Raman scattering and room temperature ferromagnetism in Co-doped SrTiO₃ particles by Dongsheng Yao; Xueyun Zhou; Shihui Ge (pp. 9233-9236).

► Co-doped SrTiO₃ nanoparticles were prepared using Sol-Gel method. ► Xps shows the existence of oxygen vacancies in SrTiO₃ and Co-SrTiO₃. And Co doping results in more oxygen vacancies. ► Raman scattering and ferromagnetic property were investigated. ► Both of Ferromagnetism and crystal deformation have a same dependence on Fe concentration and annealing temperature. ► Crystal deformation and oxygen vacancies contribute to ferromagnetism in Co-doped SrTiO₃ samples at the same time.Raman scattering has been used to study the influence of cobalt, an effective dopant to obtain SrTiO₃ magnetic oxide, on the lattice dynamics of SrTiO₃. It is found that Co doping increases the lattice defects and induces a Raman vibration mode of 690cm⁻¹. On the other hand, the ferromagnetism dependence on the x and annealing temperature was clearly and coherently observed in SrTi1−_xCo_xO₃ ( x=0, 0.01, 0.03 and 0.05) nanoparticles. It is found that the ferromagnetism of SrTi1−_xCo_xO₃ nanoparticles is weakly related to crystal deformation and oxygen vacancies in SrTiO₃. So, F-center model can explain the origin of the ferromagnetism in the prepared Co-doped SrTiO₃ samples. At the same time, the finding of large room-temperature ferromagnetism (1.6emu/g) in this system would stimulate further interest in the area of more complicated ternary oxides.

Keywords: SrTi; 1−; _x; Co; _x; O; ₃; Raman scattering; Ferromagnetism

Investigation of chemical bath deposition of CdO thin films using three different complexing agents by Hani Khallaf; Chia-Ta Chen; Liann-Be Chang; Oleg Lupan; Aniruddha Dutta; Helge Heinrich; A. Shenouda; Lee Chow (pp. 9237-9242).

► Chemical bath deposition of CdO thin films using three different complexing agents is investigated. ► As-grown films are mainly cubic CdO₂, with some Cd(OH)₂ and CdO phases being detected. ► The band gap of as-grown films is around 3.37–4.64eV, and about 2.53eV for annealed films. ► RBS reveals cadmium to oxygen ratios of about 1.00:1.74±0.01 and 1.00:1.00±0.01 for as-grown and annealed films, respectively. ► A carrier density as high as 1.89×10²⁰cm⁻³ and a resistivity as low as 1.04×10⁻²Ω-cm are obtained.Chemical bath deposition of CdO thin films using three different complexing agents, namely ammonia, ethanolamine, and methylamine is investigated. CdSO₄ is used as Cd precursor, while H₂O₂ is used as an oxidation agent. As-grown films are mainly cubic CdO₂, with some Cd(OH)₂ as well as CdO phases being detected. Annealing at 400°C in air for 1h transforms films into cubic CdO. The calculated optical band gap of as-grown films is in the range of 3.37–4.64eV. Annealed films have a band gap of about 2.53eV. Rutherford backscattering spectroscopy of as-grown films reveals cadmium to oxygen ratio of 1.00:1.74±0.01 while much better stoichiometry is obtained after annealing, in accordance with the X-ray diffraction results. A carrier density as high as 1.89×10²⁰cm⁻³ and a resistivity as low as 1.04×10⁻²Ω-cm are obtained.

Keywords: CdO; Thin films; Group II–VI Semiconductors; Chemical bath deposition

Scratch direction and threshold force in nanoscale scratching using atomic force microscopes by Ampere A. Tseng; Chung-Feng Jeffrey Kuo; Shyankay Jou; Shinya Nishimura; Jun-ichi Shirakashi (pp. 9243-9250).

► The nanoscale scratching characteristics of using a pyramidal tip was experientially studied. ► Both the scratched profile and the scratch force were greatly affected by the scratch direction. ► To minimize the ridge formation, the tip face should be perpendicular to the scratching direction.The nanoscaled tip in an AFM (atomic force microscope) has become an effective scratching tool for material removing in nanofabrication. In this article, the characteristics of using a diamond-coated pyramidal tip to scratch Ni–Fe thin film surfaces was experimentally investigated with the focus on the evaluation of the influence of the scratch or scan direction on the final shape of the scratched geometry as well as the applied scratch force. Results indicated that both the scratched profile and the scratch force were greatly affected by the scratch direction. It has been found that, to minimize the formation of protuberances along the groove sides and to have a better control of the scratched geometry, the tip face should be perpendicular to the scratching direction, which is also known as orthogonal cutting condition. To demonstrate the present findings, three groove patterns have been scratched with the tip face perpendicular to the scratching direction and very little amount of protuberances was observed. The threshold scratch force was also predicted based on the Hertz contact theory. Without considering the surface friction and adhesive forces between the tip and substrate, the threshold force predicted was twice smaller than the measurement value. Finally, recommendations for technical improvement and research focuses are provided.

Keywords: Atomic force microscopy; Contact force; Machining; Morphology; Nanofabrication; Scratching; Scanning direction; Scratch direction; Threshold force

Microstructure and surface mechanical properties of pulse electrodeposited nickel by A. Ul-Hamid; H. Dafalla; A. Quddus; H. Saricimen; L.M. Al-Hadhrami (pp. 9251-9259).

► Ni coatings were deposited on carbon steel substrates using dc and pulse electrodeposition. ► Pulse electrodeposition produced finer Ni grains compared to dc plating. ► Size of Ni grains increased with deposition time. ► Grain growth occurred in preferred (200) orientation. ► Pulse plated Ni exhibited higher hardness, creep and friction coefficient and lower modulus of elasticity.The surface of carbon steel was modified by electrochemical deposition of Ni in a standard Watt's bath using dc and pulse plating electrodeposition. The aim was to compare the microstructure and surface mechanical properties of the deposit obtained by both techniques. Materials characterization was conducted using field emission scanning electron microscope fitted with scanning transmission electron detector, atomic force microscope and X-ray diffractometer. Nanoindentation hardness, elastic modulus, adhesion, coefficients of friction and wear rates were determined for both dc and pulse electrodeposits. Experimental results indicate that pulse electrodeposition produced finer Ni grains compared to dc plating. Size of Ni grains increased with deposition. Both dc and pulse deposition resulted in grain growth in preferred (200) orientation. However, presence of Ni (111) grains increased in deposits produced by pulse deposition. Pulse plated Ni exhibited higher hardness, creep and coefficient of friction and lower modulus of elasticity compared to dc plated Ni.

Keywords: Pulse electrodeposition; Nickel; Microstructure; Nanoindentation

Evolution of SiGe nanoclusters and micro defects in the Si1−_xGe_x layer fabricated by two-step ion implantation and subsequent thermal annealing by Wenting Xu; Hailing Tu; Qinghua Xiao; Qing Chang; Zongfeng Li; Dali Liu (pp. 9260-9263).

► The embedded SiGe nanoclusters in Si1_-xGe_x layer were fabricated by two-step Ge ion implantation and subsequent annealing in this work. ► Two kinds of anneal processes (FA & RTA) were used. ► We found that the micro-defects can be avoided by RTA process, which anneal time should less than 480 s. ► The structural properties during annealing were discussed in detail. ► Additionally, the phonon confinement effect has been found by the Si-Si phonon modes investigation obtained from the Si matrix and SiGe layer, respectively.The Si1−_xGe_x thin layer is fabricated by two-step Ge ion implantation into (001) silicon. The embedded SiGe nanoclusters are produced in the Si1−_xGe_x layer upon further annealing. The number and size of the nanoclusters changed due to the Ge diffusion during annealing. Micro defects around the nanoclusters are illustrated. It is revealed that the change of Si–Si phonon mode is causing by the nanoclusters and micro defects.

Keywords: Si; 1−; _x; Ge; _x; Nanoclusters; Micro defect; Ion implantation; Annealing

Micropatterning and transferring of polymeric semiconductor thin films by hot lift-off and polymer bonding lithography in fabrication of organic field effect transistors (OFETs) on flexible substrate by Xinhong Yu; Zhe Wang; Sunyang Yu; Dongge Ma; Yanchun Han (pp. 9264-9268).

► We introduced a micropatterning and transferring process uses mechanical adhesion as the patterning-driven-force. ► This process can be used to fabricate polymeric transistors on flexible substrate. ► The transistor has a higher mobility compared with that using spin coated semiconductor layer by avoiding the solvent effect.Micropatterning and transferring of polymeric semiconductor thin films by hot lift-off and polymer bonding lithography in fabrication of OFETs with polymeric dielectric on the flexible substrate was proposed. The desired polymeric semiconductor patterns were fabricated on the flat polydimethylsiloxane (PDMS) surface with a selective lift-off method we proposed previously. The isolated and well defined polymeric semiconductor patterns left on the flat PDMS surface can be further transferred to the gate polymeric dielectric surface by polymer bonding lithography due to the low interfacial energy of PDMS. The transistor fabricated with this ‘dry’ process has a higher field-effect mobility compared with that using spin coated semiconductor layer.

Keywords: Hot lift-off; Polymer bonding lithography

Pulsed laser ablation of zinc selenide in nitrogen ambience: Formation of zinc nitride films by S. Simi; I. Navas; R. Vinodkumar; S.R. Chalana; Mohan Gangrade; V. Ganesan; V.P. Mahadevan Pillai (pp. 9269-9276).

► Preparation of discontinuous nanostructured Zn₃N₂ thin films from ZnSe target by pulsed laser deposition under nitrogen ambience. ► The study confers an outlook on how do various factors such as substrate temperature, reactive supplementing gas and laser-target interaction influence the film developing process during pulsed lased deposition. ► Optical band gap, refractive index and porosity of the Zn₃N₂ films are calculated.Zinc nitride (Zn₃N₂) thin films are prepared using pulsed laser deposition (PLD) from zinc selenide (ZnSe) target at different nitrogen ambient pressures viz. 1, 3, 5, 7 and 10Pa. The films prepared with nitrogen pressures 1 and 3Pa are amorphous in nature, whereas the films prepared at 5, 7 and 10Pa exhibit the presence of cubic bixbyite Zn₃N₂ structure with lattice parameter very close to bulk of Zn₃N₂. The particle size calculated by Debye Scherrer's formula is in the nano regime. Surface morphology of the films is studied by SEM and AFM analysis. Optical parameters such as band gap, refractive index and porosity of the films are calculated. Moreover, the present study confers an outlook about how do various factors such as substrate temperature, reactive supplementing gas and laser-target interaction influence the film developing process during pulsed lased deposition.

Keywords: Pulsed laser deposition; Formation of zinc nitride; Discontinuous thin films; Cubic bixbyite structure; Lattice strain; Band gap energy and porosity

Study on changes in the structure of HfSiO and HfSiON dielectrics with different annealing temperature by photoelectron spectroscopy by X.M. Yang; T. Yu; X.M. Wu; L.J. zhuge; S.B. Ge; J.J. He (pp. 9277-9281).

► We examine changes of the structure for HfSiO and HfSiON film with different annealing temperature by photoelectron spectroscopy. ► Core level photoelectron spectra have revealed the mechanism of metallization reaction at the bottom interface between the HfSiO(N) film and Si substrate under vacuum annealing. ► We find that Silicidation action occurs by annealing at 850 and 900°C for HfSiO and HfSiON film, respectively.We have investigated changes of the structure for HfSiO and HfSiON film with different annealing temperature by photoelectron spectroscopy. Core level photoelectron spectra have revealed the mechanism of metallization reaction at the bottom interface between the HfSiO(N) film and Si substrate under vacuum annealing. Silicidation action occurs by annealing at 850 and 900°C for HfSiO and HfSiON film, respectively, indicating the incorporation of nitrogen enhances the thermal stability. By annealing at 900°C, metallization reaction is rapidly promoted for the HfSiO film. For HfSiON film, Hf-nitride clusters or Hf-nitride layer and metal-silicide are formed at the bottom and upper interface, respectively, upon annealing at 950°C.

Keywords: HfSiO; HfSiON; Structure; Thermal stability

COOH-functionalisation of silica particles by Peter Majewski; Trent Albrecht; Siegfried Weber (pp. 9282-9286).

► First coating of silica with N-(phosphonomethyl)iminodiacetic acid (PMIDA). ► Synthesis in aqueous solution established. ► COOH-functionalization achieved. ► Multilayer coating of PMIDA observed via IR spectrometry.In this study COOH-functionalised silica is synthesised using phosphonate N-(phosphonomethyl)iminodiacetic acid (PMIDA) in an aqueous solution. The presence of PMIDA on the silica particles was verified using Fourier Transform Infrared Spectroscopy, X-ray Photoelectron Spectroscopy and titration. Experimentally, surface concentrations of COOH functional groups of up to about 3mmol/g_silica were achieved, whereas theoretical calculation of the maximum COOH functional group concentration gave about 1mmol/g_silica. The discrepancy may be caused by PMIDA multilayer formation on the particle.

Keywords: Functionalized silica; Carboxyl group; Phosphonates

Characterization of self-assembled decyl bis phosphonate–Collagen layers on titanium by QCM-D and osteoblast-compatibility by Yuxiang Ni; Zhiyuan Liu; Wenli Gao; Shuxin Qu; Jie Weng; Bo Feng (pp. 9287-9292).

► The stability of DBP and Collagen I layer that self-assembled on titanium was very good. ► Osteoblasts showed better activity, proliferation, and differentiation on Collagen I terminated samples and BSA adsorbed samples. ► Ti/DBP/Collagen I surface has the potentiality to provide a implant–bone interface with better biocompatibility.Quartz crystal microbalance dissipation (QCM-D) was used to monitor the layer by layer (LBL) self-assemble process of decyl bis phosphonate (DBP) and Collagen on titanium. The mass and viscoelastic properties of self-assembled layers were obtained using QCM-D. The stability of DBP and Collagen layer on titanium was tested to be very good. Osteoblasts cell culture was performed on LBL modified samples and that after BSA adsorption. The morphology of cells was observed by a scanning electron microscope (SEM). The total metabolic activity and differentiation of osteoblasts were evaluated by a metabolic assay and alkaline phosphatase (ALP) activity, respectively. These tests showed that osteoblasts have better activity, proliferation, and differentiation on Collagen terminated samples and BSA adsorbed samples.These results, along with the good biomineralization and protein adsorption abilities of Ti/DBP/Collagen surface (tested in our previous work), suggest titanium modified by this layer by layer technique has the potential application for medical implants.

Keywords: QCM-D; Titanium; Layer by layer; Decyl bis phosphonate; Collagen; Obsteoblasts

Structural, optical and magnetic properties of Cr doped ZnO microrods prepared by spray pyrolysis method by S. Yılmaz; M. Parlak; Ş. Özcan; M. Altunbaş; E. McGlynn; E. Bacaksız (pp. 9293-9298).

► This paper deals with the possible effects of Cr doping on the structural, optical and magnetic properties of ZnO micro-rods. ► X-ray photoelectron spectroscopy studies show that the electron binding energy of the Cr in ZnO is almost the same as the binding energy of Cr³⁺ states in Cr₂O₃. ► Photoluminescence studies at 10K show that the incorporation of chromium leads to a relative increase of deep level band intensity. ► Magnetic measurements indicated that the Cr-doped ZnO samples show ferromagnetic behavior at room temperature.A series of Cr-doped ZnO micro-rod arrays were fabricated by a spray pyrolysis method. X-ray diffraction patterns of the samples showed that the undoped and Cr-doped ZnO microrods exhibit hexagonal crystal structure. Surface morphology analysis of the samples has revealed that pure ZnO sample has a hexagonal microrod morphology. From X-ray photoelectron spectroscopy studies, the Cr 2p3/2 binding energy is found to be 577.3eV indicating that the electron binding energy of the Cr in ZnO is almost the same as the binding energy of Cr³⁺ states in Cr₂O₃. The optical band gap E_g decreases slightly from 3.26 to 3.15eV with the increase of actual Cr molar fraction from x=0.00 to 0.046 in ZnO. Photoluminescence studies at 10K show that the incorporation of chromium leads to a relative increase of deep level band intensity. It was also observed that Cr doped samples clearly showed ferromagnetic behavior; however, 2.5at.% Cr doped ZnO showed remnant magnetization higher than that of 1.1at.% and 4.6at.% Cr doped samples, while 4.6at.% Cr doped ZnO samples had a coercive field higher than the other dopings.

Keywords: Cr:ZnO; Micro rod; XPS; Photoluminescence; Ferromagnetism

Effects of thermal treatment on femtosecond laser fabricated diffraction gratings in polystyrene by K.L.N. Deepak; S. Venugopal Rao; D. Narayana Rao (pp. 9299-9305).

► Fabrication of efficient diffraction gratings, micro-craters are reported in bulk polystyrene. ► A maximum diffraction efficiency of 10% is reported for a buried grating fabricated at 1μJ energy, 1mm/s speed, and a period of 30μm. ► FESEM and the Raman studies confirmed that the emission from the modified regions is due to optical centers created in the laser irradiated regions and the debris. ► Increase in emission and excitation intensities due to thermal treatment given to these gratings is presented. ► Raman analysis of different modes before and after irradiation indicated disappearance and intensity change for few modes at higher irradiation doses.We report the fabrication of efficient, buried diffraction gratings and micro-craters in bulk polystyrene using femtosecond laser direct writing technique. We recorded a maximum diffraction efficiency of 10% for a buried grating fabricated at 1μJ energy, 1mm/s speed, and a period of 30μm. Buried micro-craters, with typical dimensions of ∼2μm, were achieved at low energies and high scanning speeds. From the field emission scanning electron microscope studies, the observed emission is attributed as due to the inner surface modifications and the debris settled around the voids. The fabricated gratings subjected to heat treatment were tested for the diffraction efficiency and emission at different excitation wavelengths and the observed results are presented. Raman spectra collected from the femtosecond laser modified regions revealed the disappearance of few Raman modes at high peak intensities associated with incident Gaussian laser pulse. Potential applications of these luminescent micro-craters are highlighted.

Keywords: Diffraction Gratings; Femtosecond laser writing; Emission spectrum; Excitation spectrum; Raman spectrum; Optical centers

Influence of substrate crystallography on the room temperature synthesis of AlN thin films by reactive sputtering by G.F. Iriarte; D.F. Reyes; D. González; J.G. Rodriguez; R. García; F. Calle (pp. 9306-9313).

► High-quality polycrystalline films with preferred c-axis orientation have been grown successfully on silicon and Au/Si substrates. ► AlN grew off-axis from the Si substrate but on-axis to the surface normal. ► On top of an Au layer AlN layer grows along the [0001] direction but showing a two-domain structure with two in-plane orientations rotated 30° between them. ► It is important to determine the crystallographic orientations that may arise in polycrystalline substrates since these may influence the thin film synthesis upon them.A pulsed DC reactive ion beam sputtering system has been used to synthesize aluminium nitride (AlN) thin films at room temperature by reactive sputtering. After systematic study of the processing variables, high-quality polycrystalline films with preferred c-axis orientation have been grown successfully on silicon and Au/Si substrates with an Al target under a N₂/(N₂+Ar) gas flow ratio of 55%, 2mTorr processing pressure and keeping the temperature of the substrate holder at room temperature. The crystalline quality of the AlN layer as well as the influence of the substrate crystallography on the AlN orientation has been characterized by high-resolution X-ray diffraction (HR-XRD). Best ω-FWHM (Full Width at Half Maximum) values of the (0002) reflection rocking curve in the 1μm thick AlN layers are 1.3°. Atomic Force Microscopy (AFM) measurements have been used to study the surface morphology of the AlN layer and Transmission Electron Microscopy (TEM) measurements to investigate the AlN/substrate interaction. AlN grew off-axis from the Si substrate but on-axis to the surface normal. When the AlN thin film is deposited on top of an Au layer, it grows along the [0001] direction but showing a two-domain structure with two in-plane orientations rotated 30° between them.

Keywords: AlN; Reactive sputtering; Thin films; Surface science

Casting mold patterning for lateral capillary force migration on PDMS microchannel by Kim Yong-Hoon; Tsuneo Urisu (pp. 9314-9317).

The casting molds including various shapes within axial and lateral resolution (110μm and 5μm) could be precisely fabricated and were suitable for the fabrication of PDMS microchannel possessing the larger inner volume for the purpose of the rapid capillary force migration. The tight bonding between PDMS mold and SiO₂/Si surface not only was governed by the flexibility and the degree of tilted angle (TA) of PDMS microchannel which shows the minimum value at the 0.2 weight ratio ( W_r) of curing agent but also efficiently generates the capillary migration.

Keywords: PDMS; Lateral capillary force; Rectangular microchannel; Bending

Effect of growth time on the structure, Raman shift and photoluminescence of Al and Sb codoped ZnO nanorod ordered array thin films by Wen-Wu Zhong; Fa-Min Liu; Lu-Gang Cai; Xue-Quan Liu; Yi Li (pp. 9318-9322).

► Al and Sb codoped ZnO nanorod ordered array thin films were synthesized using hydrothermal method. ► These films have great Raman shift of 15cm⁻¹ to lower wavenumber and have low asymmetrical factor Г_a/ Г_b of 1.17. ► These films have more donor-related PL.Al and Sb codoped ZnO nanorod ordered array thin films have been deposited on glass substrate with a ZnO seed layer by hydrothermal method at different growth time. The effect of growth time on structure, Raman shift, and photoluminescence (PL) was studied. The thin films at growth time of 5h consist of nanorods growth vertically oriented with ZnO seed layer, and the nanorods with an average diameter of 27.8nm and a length of 1.02μm consist of single crystalline wurtzite ZnO crystal and grow along [001] direction. Raman scattering analysis demonstrates that the thin films at the growth time of 5h have great Raman shift of 15cm⁻¹ to lower wavenumber and have low asymmetrical factor Г_a/ Г_b of 1.17. Room temperature photoluminescence reveals that there is more donor-related PL in films with growth time of 5h.

Keywords: PACS; 81.07.−b; 81.05.DzZnO thin film; Nanorod; Growth time; Raman spectra; Photoluminescence

Synthesis and characterization of β-Ga₂O₃ nanostructures grown on GaAs substrates by R. Jangir; Tapas Ganguli; Pragya Tiwari; S. Porwal; Himanshu Srivastava; S.K. Rai; B.Q. Khattak; S.M. Oak (pp. 9323-9328).

► Synthesis of Gallium oxide nanostructure by thermal annealing method. ► Gold coated GaAs used as substrates. ► Study of optical properties affected by doping present in GaAs substrates. ► Photoluminescence is dependent on dopant present in the GaAs.β-Ga₂O₃ nanostructures including nanowires, nanoribbons and nanosheets were synthesized via thermal annealing of gold coated GaAs substrates in N₂ ambient. GaAs substrates with different dopants were taken as the starting material to study the effect of doping on the growth and photoluminescence properties of β-Ga₂O₃ nanostructures. The nanostructures were investigated by Grazing Incident X-ray Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, Energy Dispersive X-ray Spectroscopy, room temperature photoluminescence and optical absorbance. The selected area electron diffraction and High resolution-TEM observations suggest that both nanowires and nanobelts are single crystalline. Different growth directions were observed for nanowires and nanoribbons, indicating the different growth patterns of these nanostructures. The PL spectra of β-Ga₂O₃ nanostructures exhibit a strong UV-blue emission band centered at 410nm, 415nm and 450nm for differently doped GaAs substrates respectively. A weak red luminescence peak at 710nm was also observed in all the samples. The optical absorbance spectrum showed intense absorption features in the UV spectral region. The growth and luminescence mechanism in β-Ga₂O₃ nanostructures are also discussed.

Keywords: PACS; 81.07.−b; 81.10.Bk; 78.67.Uh; 62.23.HjOptical absorption; Photoluminescence; β-Ga; ₂; O; ₃; , Nanosheets; Nanowires

Structural stabilities and diffusion of small Fe clusters on Fe (110) surface: A molecular dynamics study by Changqing Wang; Yongsheng Zhang; Yu Jia (pp. 9329-9334).

► In this study, using Embedded-atom-method (EAM) potential of iron, structural stabilities of small Fe clusters on a Fe (110) surface have been investigated by molecular dynamics studies. ► Tetramer and heptamer are more stable relatively than the other size clusters. ► A dimer diffuses more easily with lower energy barrier than a corresponding monomer. ► The shearing motion of a dimer belonging to a compact cluster can reduce diffusion barrier in the process of bigger clusters (n>3) diffusion on the Fe (110) surface. This mechanism may aid adatoms clusters diffusion activation on this surface.Using Embedded-atom-method (EAM) potential of iron, structural stabilities of small Fe clusters on a Fe (110) surface have been investigated by molecular dynamics studies. It is presented that a tetramer and heptamer clusters are more stable than other sizes. These two clusters have high transition energies. They can be a critical nucleus at low and high temperature, respectively. A dimer diffuses more easily with lower energy barrier than single adatom. The trimer's rotation and dimer shearing mechanisms have been investigated in this paper.

Keywords: EAM potential; Molecular dynamics; Diffusion; Iron; Cluster; Adsorption

Characterization of silane layers on modified stainless steel surfaces and related stainless steel–plastic hybrids by Mari Honkanen; Maija Hoikkanen; Minnamari Vippola; Jyrki Vuorinen; Toivo Lepistö; Petri Jussila; Harri Ali-Löytty; Markus Lampimäki; Mika Valden (pp. 9335-9346).

► AFM, FESEM, and TEM are useful to obtain quantitative information on silane layers. ► Information on layers can be linked to adhesion and failure type of hybrids. ► Controlled Fe₂O₃-type surface is needed to achieve uniform silane layer. ► Silane layer on controlled oxide layer has more N-species to react with plastic.The aim of this work was to characterize silane layers on the modified stainless steel surfaces and relate it to the adhesion in the injection-molded thermoplastic urethane–stainless steel hybrids. The silane layers were characterized with scanning electron microscope and transmission electron microscope, allowing the direct quantization of silane layer thickness and its variation. The surface topographies were characterized with atomic force microscope and chemical analyses were performed with X-ray photoelectron spectroscopy. The mechanical strength of the respective stainless steel–thermoplastic urethane hybrids was determined by peel test. Polishing and oxidation treatment of the steel surface improved the silane layer uniformity compared to the industrially pickled surface and increased the adhesion strength of the hybrids, resulting mainly cohesive failure in TPU. XPS analysis indicated that the improved silane bonding to the modified steel surface was due to clean Fe₂O₃-type surface oxide and stronger interaction with TPU was due to more amino species on the silane layer surface compared to the cleaned, industrially pickled surface. Silane layer thickness affected failure type of the hybrids, with a thick silane layer the hybrids failed mainly in the silane layer and with a thinner layer cohesively in plastic.

Keywords: Metal–plastic hybrids; Silane; AFM; TEM; SEM; XPS

Controlled Cu content of electrodeposited CoCu nanowires through pulse features and investigations of microstructures and magnetic properties by M. Almasi Kashi; A. Ramazani; F. Adelnia Najafabadi; Z. Heydari (pp. 9347-9350).

► CoCu alloy nanowire arrays were fabricated by ac pulse electrodeposition. ► Controlling off-times form nanowires with Co, Cu and CoCu mixed crystal phases. ► Easy to perform technique based on control of off-time and Cu concentration. ► Hc and S were increased twice as the off-time between pulses increased to 200ms.CoCu alloy nanowire arrays embedded in anodic alumina template were fabricated by ac pulse electrodeposition. Different off-times between pulses in an electrolyte with constant concentration of Co⁺² and Cu⁺² and acidity of 4 were employed. The effect of deposition parameters on the alloy contents, microstructures and magnetic properties of Co_xCu1−_x nanowires were studied. It is shown that Co content decreased by increasing the off-time between pulses in a wide range ( x=0.53–0.07). These results are in consistence with saturation magnetization, which was reduced with increase in the off-time between pulses. It was also found that by optimizing the off-times, it is possible to fabricate CoCu nanowires with mixed phase of hcp Co, fcc Cu and fcc CoCu crystal phase.

Keywords: PACS; 75.30.GW; 75.60.Ej; 75.75.+aMagnetic alloy nanowire; Pulse electrodepsition; Porous anodic aluminum oxide

Thermal stability and electrical characteristics of NiSi films with electroplated Ni(W) alloy by Yuhang Xin; Anmin Hu; Ming Li; Dali Mao (pp. 9351-9354).

► Electroplating deposited NiW alloying films as diffusion barrier layers. ► The barrier performance of NiW films was improved with W atom blocked. ► Cu atom is hardly diffuse through NiW barrier layer. ► The stacked Si/Ni(W)/Cu films is perfect at 600°C.In this study, an electroplating method to deposited Ni, crystalline NiW(c-NiW), amorphous NiW (a-NiW) films on P-type Si(100) were used to form Ni-silicide (NiSi) films. After annealed at various temperatures, sheet resistance of Ni/Cu, c-NiW/Cu and a-NiW/Cu was measured to observe the performance of those diffusion barrier layers. With W added in the barrier layer, the barrier performance was improved. The results of XRD and resistance measurement of the stacked Si/Ni(W)/Cu films reveal that Cu atom could diffuse through Ni barrier layer at 450°C, could diffuse through c-NiW at 550°C, but could hardly diffuse through a-NiW barrier layer. c-NiW layer has a better barrier performance than Ni layer, meanwhile the resistance is lower than a-NiW layer.

Keywords: Electroplate; Metal silicide; Nickel tungsten alloy; Diffusion barrier layer

(Mo+N) codoped TiO₂ for enhanced visible-light photoactivity by Hailin Liu; Zhihong Lu; ling Yue; Jing Liu; Zhanghua Gan; Chang Shu; Ting Zhang; Jing Shi; Rui Xiong (pp. 9355-9361).

► Mo or N mono-doped and (Mo+N) co-doped anatase TiO₂ nanoparticles have been fabricated by sol-gel method. ► (Mo+N) co-doped TiO₂ has high photo absorption in whole visible region. ► Band structure calculations indicate more impurity bands can be induced by co-doping. ► The up-limit of dopant concentrations is increased by co-doping. ► (Mo+N) co-doped TiO₂ is promising to have high photocatalystic efficiency under visible light.A series of Ti1−_xMo_xO2−_yN_y samples were prepared by using sol–gel method and characterized by X-ray diffraction, transmission electron microscopy and UV–vis absorption spectroscopy. All Ti1−_xMo_xO2−_yN_y samples are anatase phase. It is found that Mo, N mono-doping can increase visible light absorption, while (Mo+N) co-doping can greatly enhance absorption in whole visible region. Results of our first-principles band structure calculations reveal that (Mo+N)-doping, especially passivated co-doping can increase the up-limit of dopant concentration and create more impurity bands in the band gap of TiO₂, which leads to a greatly increase of its visible-light absorption without a decrease of its redox potential. It reveals that (Mo+N) co-doped TiO₂ is promising for a photocatalyst with high photocalystic activity under visible light.

Keywords: Key words; (Mo; +; N) codoped TiO; ₂; Photoactivity; Sol–gel method; First-principles band structure calculations

Fabrication of a superhydrophobic surface on a wood substrate by Shuliang Wang; Junyou Shi; Changyu Liu; Cheng Xie; Chengyu Wang (pp. 9362-9365).

A layer of lamellar super-hydrophobic film was fabricated on wood surface through a wet chemical method. The super-hydrophobic property of the wood surface was measured by contact angle measurements (CA). The microstructure and chemical composition of the super-hydrophobic film was analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Analytical characterization revealed that the micro-scale roughness lamellar particles uniformly erect on the wood surface and mutually structure the cellular structure, the Zinc stearate (hydrophobic groups toward the outside) monolayer deposits on the ZnO surface which results from the reaction of stearic acid and ZnO, thus transforming the wood surface from hydrophilic to super-hydrophobic with a water contact angle 151°, and the sliding angle is less than 5°.Display Omitted► A facile and simple method was utilized to produce the superhydrophobic wood. ► The research referring to superhydrophobic wood is novel. ► The wettability of wood surface changed from hydrophilic to superhydrophobic. ► The synthesis of superhydrophobic wood may contribute to the enlarger use of wood.A layer of lamellar superhydrophobic coating was fabricated on a wood surface through a wet chemical process. The superhydrophobic property of the wood surface was measured by contact angle (CA) measurements. The microstructure and chemical composition of the superhydrophobic coating were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). An analytical characterization revealed that the microscale roughness of the lamellar particles was uniformly distributed on the wood surface and that a zinc stearate monolayer (with the hydrophobic groups oriented outward) formed on the ZnO surface as the result of the reaction between stearic acid and ZnO. This process transformed the wood surface from hydrophilic to superhydrophobic: the water contact angle of the surface was 151°, and the sliding angle was less than 5°.

Keywords: Superhydrophobic; ZnO coating; Stearic acid; Wood surface

Successful incorporation of multi-walled carbon nanotubes in nickel electrodeposited coating by electrophoresis by S. Khabazian; S. Sanjabi (pp. 9366-9370).

► A novel root was suggested for synthesis of nickel–MWCNT composite coatings by combining EPD and electrodeposition. ► A homogenous and adhesive multi-walled carbon nanotube (MWCNT) coating was electrophoretically deposited on stainless steel from an aqueous solution by applying high strength electric fields. ► The results showed a great enhancement in hardness of the coatings due to the increasing of carbon content up to 12.5wt% which is much higher than the results of previous works. ► A perfect combination between MWCNTs and the nickel matrix results in the formation of an armed concrete like structure adhered firmly to the substrate. ► This procedure could be used for fabrication of other metals and alloy matrix composites, with high contents of well-distributed carbon nanotubes.A homogenous and adhesive multi-walled carbon nanotube (MWCNT) coating was electrophoretically deposited on stainless steel from an aqueous solution by applying high strength electric fields. Then, nickel was electrodeposited on MWCNT films. MWCNTs content in the composite coatings was reached to 12.5wt% which was much higher than the content of MWCNTs in conventional nickel–MWCNT electrodeposited coatings. The hardness value of composite coatings significantly increased up to 870 Vickers which it was measured by both micro and nanohardness tests.

Keywords: Electrodeposition; Nickel; Multi-walled carbon nanotube; Composite

Composite coating of 58S bioglass and hydroxyapatite on a poly (ethylene terepthalate) artificial ligament graft for the graft osseointegration in a bone tunnel by Hong Li; Yang Wu; Yunsheng Ge; Jia Jiang; Kai Gao; Pengyun Zhang; Lingxiang Wu; Shiyi Chen (pp. 9371-9376).

► Hydroxyapatite and bioglass composited materials were coated on PET artificial ligament graft using gelatin as a carrier. ► Cell biocompatibity and bioactivity was improved on HA/BG composite coated grafts. ► HA/BG composite coating enhanced the graft osseointegration within the host bone tunnel.The purpose of this study was to determine the effect of the combination of hydroxyapatite (HA) and bioglass (BG) on polyethylene terephthalate (PET) artificial ligament graft osseointegration within the bone tunnel. The results of in vitro culturing of MC3T3-E1 mouse osteoblastic cells proved that this HA/BG composite coating can promote the cell compatibility of grafts. A rabbit extraarticular tendon-to-bone healing model was used to evaluate the effect of this composite coating on PET artificial ligaments in vivo. The final results demonstrated that HA/BG coating improved new bone formation at the graft-bone interface and increased the load-to-failure property of graft in bone tunnel compared to the control group at early time. The study has shown that HA/BG composite coating on the PET artificial ligament surface has a positive effect in the induction of artificial ligament osseointegration within the bone tunnel.

Keywords: Polyethylene terephthalate; Hydroxyapatite; Bioglass; Osseointegration; Artificial ligament

Thermodynamic parameters of Bi₂Sr₂CaCu₂O8+_δ thin film prepared by molecular beam epitaxy by Bingsen Zhang; Yang Qi (pp. 9377-9381).

► Bi-based oxide thin films have been successfully fabricated by molecular beam epitaxy. ► The phase formation in Bi₂Sr₂CaCu₂O8+_δ films was investigated as a function of oxidizing gas pressure and substrate temperature. ► The ozone partial pressure-substrate temperature phase diagram has been established in the Bi₂Sr₂Ca_nCu n₊₁O_m ( n=1, 2, 3) thin films. ► The thermodynamic parameters have been investigated through enthalpy change in the growth process of Bi-based thin films.Bi₂Sr₂CaCu₂O8+_δ (Bi2212) thin film is an important superconducting material ascribed to its high transition temperatures and low toxicity, but the application of Bi2212 thin films is limited due to the appearances of intergrowth and impurity phases. To achieve high-quality Bi2212 thin film by molecular beam epitaxy (MBE), the oxidizing gas pressure and substrate temperature are the key parameters. Here, the phase formation in Bi-based thin films grown by MBE was studied as a function of oxidizing gas pressure and substrate temperature. Furthermore, the thermodynamic parameters have been investigated through enthalpy change. This study indicates that the substrate temperature was increased with the enhancing of ozone partial pressure when the composition ratio is fixed, Bi2212 single phase can be formed. Moreover, the chemical stability decreases in the order of Bi₂Sr₂CuO6+_δ>Bi2212>Bi₂Sr₂Ca₂Cu₃O10+_δ.

Keywords: Thin film; Bi-based oxides; Substrate temperature; Ozone partial pressure

Stable organic solar cells employing MoO₃-doped copper phthalocyanine as buffer layer by Guohua Cao; Linsen Li; Min Guan; Jie Zhao; Yiyang Li; Yiping Zeng (pp. 9382-9385).

► Organic heterojunction photovoltaic solar cells with MoO₃-doped CuPc as buffer layer. ► The lifetime of device with MoO₃-doped CuPc can be improved. ► A charge transfer (CT) complex between CuPc and MoO₃ forming. ► Surface maximum roughness was plays a decisive role in improving the stability.A stable organic solar cell with structure of ITO/buffer/donor/acceptor/cathode is presented. A thin layer (5nm) of MoO₃-doped CuPc is adopted as the buffer in CuPc/C₆₀ organic heterojunction photovoltaic (PV) solar cells, resulting in two times longer lifetime. The surface morphology of buffer layer plays a decisive role in improving the stability.

Keywords: Organic solar cells; MoO; ₃; -doped CuPc film; Buffer layers; Surface morphology

Effect of molecular structure on bias stress effect in organic thin-film transistors by A.K. Diallo; F. Fages; F. Serein-Spirau; J.-P. Lère-porte; C. Videlot-Ackermann (pp. 9386-9389).

► Role of the molecular structure of two news oligomers involved as active layer in thin-film devices. ► Comparison with the well-known p-type semiconductor: pentacene. ► Impact of molecular structure and associated thin film morphology on bias stress effect.Two thiophene-phenylene semiconductors, bis(2-phenylethynyl) end-substituted oligothiophenes (diPhAc- nTs, n=2, 3), were studied as active layers in organic thin film transistors (OTFTs). Structural and electrical properties of such high vacuum evaporated thin films were compared to pentacene. All three oligomers behave as p-type semiconducting layers into OTFTs. In the same preparation and measurement conditions, diPhAc-3T possesses two of incontrovertible attributes of OTFTs for low cost applications, a high air-stable mobility at low substrate temperature ( T_sub), i.e. typically 25°C together with a reduced bias stress effect compared to the well-known pentacene semiconductor. This study brings to light on the role of the molecular structure involved in the active layer in thin-film devices and describes effects as thin film morphology as important parameters when optimizing the structure of OTFTs.

Keywords: Oligomers; Thin films; Transistors; Bias stress effect

Electrochemical DNA biosensor based on avidin–biotin conjugation for influenza virus (type A) detection by Da-Jung Chung; Ki-Chul Kim; Seong-Ho Choi (pp. 9390-9396).

► This manuscript presented the fabrication of electrochemical DNA (E-DNA) biosensors by avidin–biotin conjugation of a biotinylated probe DNA. ► The probe DNA, 5′-biotin-ATG AGT CTT CTA ACC GAG GTC, was immobilized on the avidin-modified glassy carbon electrode to detect influenza virus (type A). ► The current value measured by cyclic voltammetry (CV) was decreased after hybridization of the probe DNA and target DNA.An electrochemical DNA biosensor (E-DNA biosensor) was fabricated by avidin–biotin conjugation of a biotinylated probe DNA, 5′-biotin-ATG AGT CTT CTA ACC GAG GTC GAA-3′, and an avidin-modified glassy carbon electrode (GCE) to detect the influenza virus (type A). An avidin-modified GCE was prepared by the reaction of avidin and a carboxylic acid-modified GCE, which was synthesized by the electrochemical reduction of 4-carboxyphenyl diazonium salt. The current value of the E-DNA biosensor was evaluated after hybridization of the probe DNA and target DNA using cyclic voltammetry (CV). The current value decreased after the hybridization of the probe DNA and target DNA. The DNA that was used follows: complementary target DNA, 5′-TTC GAC CTC GGT TAG AAG ACT CAT-3′ and two-base mismatched DNA, 5′-TTC GAC AGC GGT TAT AAG ACT CAT-3′.

Keywords: E-DNA biosensor; Electrochemical reduction; Avidin–biotin conjugation; Hybridization; Influenza virus (type A)

Synthesis and characterization of Fe₃O₄@C@Ag nanocomposites and their antibacterial performance by Haiqing Xia; Bin Cui; Junhong Zhou; Lulu Zhang; Ji Zhang; Xiaohui Guo; Huilin Guo (pp. 9397-9402).

► To enhance the efficiency of antibacterial of Ag nanoparticles and recycle the residual Ag nanoparticles in the system, we synthesized Fe₃O₄@C@Ag and Fe₃O₄@Ag nanocomposites. ► For the role of intermediate carbon layer, antibacterial properties of Fe₃O₄@C@Ag is better than Fe₃O₄@Ag. ► The Fe₃O₄@C@Ag nanocomposites will have potential uses in many fields as catalysts, absorbents, and bifunctional magnetic–optical materials.We synthesized Fe₃O₄@C@Ag nanocomposites through a combination of solvothermal, hydrothermal, and chemical redox reactions. Characterization of the resulting samples by X-ray diffraction, Fourier-transform infrared spectroscopy, field-emission scanning and transmission electron microscopy, and magnetic measurement is reported. Compared to Fe₃O₄@Ag nanocomposites, the Fe₃O₄@C@Ag nanocomposites showed enhanced antibacterial activity. The Fe₃O₄@C@Ag nanocomposites were able to almost entirely prevent growth of Escherichia coli when the concentration of Ag nanoparticles was 10μg/mL. Antibacterial activity of the Fe₃O₄@C@Ag nanocomposites was maintained for more than 40h at 37°C. The intermediate carbon layer not only protects magnetic core, but also improves the dispersion and antibacterial activity of the silver nanoparticles. The magnetic core can be used to control the specific location of the antibacterial agent (via external magnetic field) and to recycle the residual silver nanoparticles. The Fe₃O₄@C@Ag nanocomposites will have potential uses in many fields as catalysts, absorbents, and bifunctional magnetic–optical materials.

Keywords: Composites; Magnetic materials; X-ray diffraction; Magnetic properties

Quality improvement of single-walled carbon nanotubes by doping B in Fe/MgO catalyst by Yunfang Liu; Yan Pan; Weidong Chi; Zengmin Shen (pp. 9403-9406).

► The quality of single-walled carbon nanotubes can be effectively improved by doping appropriate amount of B in the Fe/MgO catalyst. ► The research results shed light on the importance of radical species on the formation of carbon nanotube. ► This method contributes to the understanding of nanotube growth mechanism.We demonstrate that the quality of the as-grown single-walled carbon nanotubes (SWCNTs) can be effectively improved by the addition of the B ingredient in the Fe/MgO catalyst. The as-grown SWCNTs were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The SWCNTs prepared by the pure Fe/MgO catalyst have relatively low graphite crystallinity and are coated by much amorphous carbon. The intensity ratio of the D- and G-bands ( I_D/ I_G) in Raman spectra is relatively high (0.098 for laser 532nm and 0.075 for laser 785nm). The SWCNTs grown from the Fe/MgO catalyst doped with 0.1 part of B have more regular graphite structure with little amorphous carbon. The I_D/ I_G values reduced remarkably (0.041 for laser 532nm and 0.040 for laser 785nm). The effect would be attributed to the inhibitory action of the doped B on the formation of radical hydrocarbon species for the formation of SWCNTs.

Keywords: Single-walled carbon nanotube; Catalyst; Electron microscopy; Raman spectroscopy

Chitosan cushioned phospholipid membrane and its application in imaging ellipsometry based-biosensor by Yibang Zhang; Yanyan Chen; Gang Jin (pp. 9407-9413).

► Air stable phospholipid membrane microarray is formed on silicon surface. ► Polymer sandwiched membrane shows strong nonspecific adsorption resistance against serum. ► Preliminary application in the immunoassay is shown by imaging ellipsometry-based biosensor.Chitosan cushion can support the air stability of phospholipid membrane, but the problem of serum solubility of phospholipid membrane prevents it from use in serum detection applications. Poly (ethylene glycol) (PEG) shielding promises both stability and non-specific adsorption resistance for phospholipid membrane. An air stable phospholipid membrane microarray has been successfully fabricated on chitosan modified silicon wafer. We have demonstrated the potential application of PEGylated phospholipid membrane in imaging ellipsometry-based protein biosensor. Because of the strong resistance against non-specific adsorption of serum, antigens are immobilized onto the membrane surface through chemical activation and further bind their antibodies without using blocking agent. Taking advantage of the multiple and parallel reaction capabilities of microfluidic reactor system, we have assayed the binding by varying both the density of antigen on the membrane surface and the concentration of antibody in solution.

Keywords: Phospholipid membrane; Chitosan; Imaging ellipsometry; Biosensor; AFM

Accurate depth profiling of dry oxidized SiGeC thin films by extended Full Spectrum ToF-SIMS by M. Py; E. Saracco; J.F. Damlencourt; J.P. Barnes; J.M. Fabbri; J.M. Hartmann (pp. 9414-9419).

► Oxidation of SiGeC blanket layers for Ge enrichment is studied with ToF-SIMS. ► An original quantification protocol, the extended Full Spectrum protocol, is used. ► Improvements brought by this protocol over more classic ones are highlighted. ► This study yields useful information for comprehension of the oxidation mechanisms.The abundance of work on SiGe based devices demonstrates the importance of compositional characterization of such materials. However accurate SIMS depth profiling of SiGe, and especially of SiGe/silicon dioxide interfaces can be difficult due to matrix effects.Therefore, we highlight here the improvements brought by the extended Full Spectrum protocol, presented in previous works and allowing minimization of matrix effects. Previous studies on this protocol showed that it was extremely precise and reproducible for Ge and impurity quantification in non oxidized matrices. In this study we thus investigated its accuracy for simultaneous quantitative depth profiling of both matrix elements (Si, Ge, O) and impurities (C) in Si_0.82Ge_0.16C_0.02 layers annealed in oxidizing atmosphere, by comparing results with more classic protocols. The profiles provided by the extended Full Spectrum protocol were found to be more accurate than the others, especially around interfaces. This results in a better comprehension of the behaviour of SiGeC layers under oxidizing anneal and thus allows the fabrication of very well controlled three dimensional Ge nanowire structures for next generation devices.

Keywords: Silicon Germanium; ToF-SIMS; Full Spectrum; Ge condensation

Atomic layer deposition coating of ZnO shell for GaN–ZnO core-sheath heteronanowires by Hyoun Woo Kim; Ju Chan Yang; Han Gil Na; Chongmu Lee (pp. 9420-9424).

► Synthesis of GaN–ZnO core–shell heteronanowires. ► Coating of thin (<10nm) ZnO shell by atomic layer deposition. ► The ZnO shell significantly affected photoluminescence.We have synthesized GaN-core/ZnO-shell nanowires and investigated effects of the ZnO coating. The X-ray diffraction pattern showed that as-synthesized samples are composed of GaN and ZnO. Transmission electron microscopy indicated that the deposited ZnO shell layer is poly-crystalline. The photoluminescence (PL) spectrum of GaN has been changed by the ZnO coating, where emission bands centered at roughly 1.9eV, 2.5eV, and 3.3eV were newly added to the emissions from core GaN nanowires. We found that overall PL intensity has been significantly increased by coating the ZnO shell layers.

Keywords: PACS; 81.05.Hd; 78.55.−mNanostructures; Chemical synthesis; Transmission electron microscopy

Fabrication, characterization and some applications of graded chiral zigzag shaped nano-sculptured silver thin films by Hadi Savaloni; Ali Esfandiar (pp. 9425-9434).

► Zigzag shaped silver chiral graded sculptured thin films are produced. ► TM and LM modes of plasmon resonances are observed. ► Field ionization gas sensing results obtained are comparable to those of nano-tubes.Graded chiral zig–zag shaped nano-sculptured silver thin films (GCZSSTF) were produced in two stages using oblique deposition technique together with rotation of substrate about its surface normal while a shadowing block was also fixed at the center of the substrate holder. Chrystallographic and morphological structure of these films were obtained using X-ray diffraction (XRD) and atomic force microscopy (AFM). Spectrophotometry was used to obtain their optical behavior while their application in both hydrophobicity and gas sensing was also investigated. XRD results showed a dominant (111) orientation growth on the zig arm of the structure while by addition of the second arm (zag) the crystallographical growth orientation changed to (220).The anisotropic nano-structure of these films was also distinguished through (1− R) spectra. A common peak at about 350nm related to the TM mode of plasmon resonances and a broad shoulder at about 420nm for the s-polarized light and at 620nm for the p-polarized light corresponding to the LM mode of plasmon resonances are observed. These peaks are directly related to the nano-columns topography. The film system used here proved to act as a physical method for producing layer-by-layer structure for obtaining enhanced hydrophobic surfaces rather than the usual chemical methods reported in the literature. In addition, the GCZSSTF also acted as good as reported results for nano-tubes when applied as cathode in the field ionization gas sensing setup.

Keywords: Graded chiral zig–zag; Silver; Oblique angle deposition; Sculptured thin films; Hydrophobicity; Field ionization gas sensors

Vermiculite decorated with copper nanoparticles: Novel antibacterial hybrid material by Jaroslaw Drelich; Bowen Li; Patrick Bowen; Jiann-Yang Hwang; Owen Mills; Daniel Hoffman (pp. 9435-9443).

Display Omitted► We embedded vermiculite with nanoparticles of elemental copper. ► Copper nanoparticles reside on surfaces of vermiculite platelets with strong adhesion. ► The hybrid material has strong antibacterial activity against Staphylococcus aureus.Vermiculite decorated with copper nanoparticles is a new antibacterial material that was prepared in this study through ion-exchange process and hydrogen reduction. The replacement of magnesium ions in interlayer structure was carried out using concentrated copper sulfate solutions at elevated temperature. Copper ions were reduced to elemental copper at 400–600°C using hydrogen as the reducing agent. During the reduction process copper diffused primarily to vermiculite surface regions and formed copper nanoparticles with a broad range of sizes, from ∼1 to 400nm. Strong adhesion of copper nanoparticles to the vermiculite carrier makes this hybrid very stable and durable. The new vermiculite-metallic copper hybrid material shows strong antibacterial activity against Staphylococcus aureus at 37°C. Vermiculite is an inexpensive mineral that is very stable under a wide range of industrial and environmental conditions, and extensively used as filler in fireproof materials, plastics, paints and lightweight concrete, so the addition of copper as an antibacterial agent opens new avenues for the application of vermiculite in consumer products and other areas.

Keywords: Antibacterial material; Copper; Vermiculite

Swelling assisted photografting of itaconic acid onto sodium alginate membranes by Gülşen Taşkın; Oya Şanlı; Gülsen Asman (pp. 9444-9450).

Display Omitted► Swelling assisted grafting method using UV radiation. ► Increase in the hydrophilicity of sodium alginate (NaAlg) membranes by grafting IA. ► Optimization of grafting conditions for IA grafted NaAlg membranes.Grafting of itaconic acid (IA) was achieved onto sodium alginate (NaAlg) membranes by using UV-radiation. Process was performed under nitrogen atmosphere and benzophenone (BP) was used as a photoinitiator. Membranes were preswelled before the polymerization process and ethanol was determined as the best swelling agent among the studied solvents. The effect of polymerization time, initiator and monomer concentrations on the grafting efficiency were investigated. The best conditions for optimum grafting were obtained with IA concentration of 1.0M, a BP concentration of 0.1M and a reaction time of 4h at 25°C. Under these conditions grafting efficiency for NaAlg–g–IA membranes was found to be 14% (w/w). To obtain further increase in grafting efficiency membranes were also preswelled in IA and BP solutions and polymerization was carried out at different temperatures after UV polymerization. Grafted membranes were characterized by using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Effect of grafting on membrane properties such as intrinsic viscosity and swelling percentage were also determined.

Keywords: Membranes; Photopolymerization; Itaconic acid; Sodium alginate; UV; Graft copolymers

Enhanced water vapor barrier properties for biopolymer films by polyelectrolyte multilayer and atomic layer deposited Al₂O₃ double-coating by Terhi Hirvikorpi; Mika Vähä-Nissi; Ali Harlin; Mikko Salomäki; Sami Areva; Juuso T. Korhonen; Maarit Karppinen (pp. 9451-9454).

Display Omitted► Enhanced water vapor barrier characteristics were realized for bio-based material. ► After coating of PEM+thin Al₂O₃ layer, the properties were significantly improved. ► Substrate was biopolymer film, coated with a polyelectrolyte multilayer (PEM) film.Commercial polylactide (PLA) films are coated with a thin (20nm) non-toxic polyelectrolyte multilayer (PEM) film made from sodium alginate and chitosan and additionally with a 25-nm thick atomic layer deposited (ALD) Al₂O₃ layer. The double-coating of PEM+Al₂O₃ is found to significantly enhance the water vapor barrier properties of the PLA film. The improvement is essentially larger compared with the case the PLA film being just coated with an ALD-grown Al₂O₃ layer. The enhanced water vapor barrier characteristics of the PEM+Al₂O₃ double-coated PLA films are attributed to the increased hydrophobicity of the surface of these films.

Keywords: Atomic layer deposition; Layer-by-layer deposition; Polyelectrolyte; Water vapor barrier; Aluminum oxide; Polylactide

A first-principles study of C+O reaction on NiCo(111) surface by Hongyan Liu; Riguang Zhang; Fangyuan Ding; Ruixia Yan; Baojun Wang; Kechang Xie (pp. 9455-9460).

Display Omitted► Build the model of NiCo(111) slab. ► Adsorption energies of C and CO are lower on NiCo(111) than those on Ni(111). ► Reaction barrier of association of C+O is increased by 0.35eV. ► Incorporation of Co into the Ni crystal is not in favor of carbon elimination.A density-functional theory method has been conducted to investigate the association of C+O on (111) facets of ordered NiCo alloy and the results have been compared with those obtained on pure Ni(111) surface. In reaction of C+O, the favorable reaction path is that C adsorbed on HCP-1 site moves to the nearest Ni–Co bridge site, and associates with O migrating from FCC-1 site to result in CO adsorbed on the bridge site of Ni–Co. However, the reaction barrier is higher by 0.35eV than that on pure Ni(111), which indicates that the incorporation of Co into the Ni crystal is not in favor of the reaction of carbon delimination.

Keywords: C; +; O reaction; Alloy surface; Reaction barrier

Electrical properties of vacuum-annealed titanium-doped indium oxide films by L.T. Yan; J.K. Rath; R.E.I. Schropp (pp. 9461-9465).

► A new phenomenon in vacuum post-annealing ITiO films is presented. ► Post-annealing is more effective in improving electron mobility for amorphous ITiO film deposited at a lower power compared with crystallized ITiO films obtained at a higher power. ► ITiO film is suitable for use as window layers for solar cells with low bandgap absorbers.Titanium-doped indium oxide (ITiO) films were deposited on Corning glass 2000 substrates at room temperature by radio frequency magnetron sputtering followed by vacuum post-annealing. With increasing deposition power, the as-deposited films showed an increasingly crystalline nature. As-deposited amorphous ITiO films obtained at 20W began to crystallize at the annealing temperature of 155°C. Although there was no significant change in the crystalline structure of the films, electron mobility improved gradually with further increase in the annealing temperature. After post-annealing at 580°C, the highest electron mobility of 50cm²V⁻¹s⁻¹ was obtained. Compared with the amorphous ITiO films, the ITiO films with a certain degree of crystallinity obtained at high deposition power were less affected by the vacuum annealing. Their electron mobility also improved due to post-annealing, but the increase was insignificant. After post-annealing, the optical transmission of the 325 nm-thick ITiO films showed approximately 80% at wavelengths ranging from 530 to 1100nm, while the sheet resistance decreased to 10Ω/sq. This makes them suitable for use as transparent conductive oxide layers of low bandgap solar cells.

Keywords: Sputtering deposition; Amorphous; Annealing; Electrical properties; Optical transmission

Effect of oxygen surface groups on adsorption of benzene derivatives from aqueous solutions onto active carbon samples by Anna Derylo-Marczewska; Bronislaw Buczek; Andrzej Swiatkowski (pp. 9466-9472).

► Dependence between surface chemistry of active carbon samples and adsorption quantity of aromatic substances was established. ► Langmuir–Freundlich equation gives best fitting for adsorption isotherms in all cases. ► Oxygen groups present on active carbon surface samples show different interaction with aromatic substances and exert effect on adsorption equilibria.The process of adsorption of selected benzene derivatives from aqueous solution is investigated on two carbonaceous materials of differentiated surface properties – quantity of oxygen functional groups. Carbon samples were prepared by removal of external layers from granules of unmodified and oxidized active carbon. The surface and structure characteristics of carbon samples were estimated by various methods. The experimental isotherms of organics adsorption from liquid phase were measured and interpreted in terms of the theory of adsorption on heterogeneous solid surfaces. The influence of differences in adsorbate and adsorbent properties on adsorption uptake was analyzed. The adsorption effectiveness was regarded as a result of the differences in adsorbate hydrophobicities and the effect of specific interactions of its functional groups with active sites on carbon surface.

Keywords: Active carbon; Surface oxygen groups; Adsorption of aromatic compounds

Photoactivated surface grafting from PVDF surfaces by Thomas Berthelot; Xuan Tuan Le; Pascale Jégou; Pascal Viel; Bruno Boizot; Cécile Baudin; Serge Palacin (pp. 9473-9479).

Display Omitted► New synthetic way to graft acrylate and methacrylate polymers on PVDF films based on activation latent species on the PVDF (i.e. oxidation) ► Photochemical activation of pre-existing defects on the PVDF surface by low-energy photons (320–500nm) ► Easy, economic and effective method to covalently attach hydrophilic polymers on PVDF films.Economic and easy methods to tune surface properties of polymers as Poly(vinylidene fluoride) (PVDF) without altering bulk properties are of major interest for different applications as biotechnological devices, medical implant device… UV irradiation appears as one of the simplest, easy and safe method to modify surface properties. In the case of self-initiated grafting, it is generally assumed that the pre-treatment of the PVDF surface with UV irradiation can yield alkyl and per-oxy radicals originating from breaking bonds and capable of initiating the subsequent surface grafting polymerizations. Surprisingly, the present work shows that it is possible to obtain polymer grafting using low energetic UV-A irradiation (3.1–3.9eV) without breaking PVDF bonds. An EPR study has been performed in order to investigate the nature of involved species. The ability of the activated PVDF surface to graft different kinds of hydrophilic monomers using the initiated surface polymerization method has been tested and discussed on the basis of ATR FT-IR, XPS and NMR HRMAS results.

Keywords: Ultraviolet-A irradiation; Polymer grafting; Poly(vinylidene fluoride); EPR study

CdS thin films growth by fast evaporation with substrate rotation by R. Castro-Rodríguez; J. Mendez-Gamboa; I. Perez-Quintana; R. Medina-Ezquivel (pp. 9480-9484).

► CdS films deposited by fast evaporation technique combined with substrate rotation. ► Source evaporation temperature was 600°C and the substrate temperature at 350°C. ► CdS films were flat with uniform thickness. ► XRD shows that it is possible tailor the CdS hexagonal or cubic phase. ► Short circuit photocurrent density losses in the glass/CdS were 6.6mA/cm².CdS thin films were grown by fast evaporation technique combined with substrate rotation. The source evaporation temperature was maintained at 600°C and the substrate temperature at 350°C with background pressure of 1.0mTorr. The substrates were corning glass 2947 with dimension of 1in.×1in. rotate at 500rpm during the growth. In order to verify the quality of the CdS films, the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and optical measurements. The films shown a flat uniformity thickness with growth rate of ∼3.5nm/s, the orientation was in the cubic-(111) and hexagonal-(002) plane in dependence of the growth time, grain size ∼5nm, roughness uniformity ∼2.7nm, transmittance in the visible region spectrum ∼80%, energy band gap between 2.39 and 2.42eV and short circuit photocurrent density ( J_SC) losses in the CdS films of 4.7mA/cm².

Keywords: Flash deposition technique; CdS thin films; Physical properties; Solar cells

Mg diffusion in K(Ta_0.65Nb_0.35)O₃ thin films grown on MgO evidenced by Auger electron spectroscopy investigation by Q. Simon; V. Bouquet; V. Demange; S. Députier; F. Wyczisk; G. Garry; A. Ziaie; M. Guilloux-Viry (pp. 9485-9489).

► Evidence of long range Mg diffusion from MgO substrate in as deposited KTN films. ► Investigation of Mg diffusion by Auger electron spectroscopy. ► Effect of annealing on homogenization of diffused Mg in KTa_0.65Nb_0.35O₃ films. ► KTa_0.65Nb_0.35O₃ thin films grown by pulsed laser deposition. ► KTa_0.65Nb_0.35O₃ epitaxially grown on MgO.The diffusion of Mg in pulsed laser deposited K(Ta_0.65Nb_0.35)O₃ thin films epitaxially grown on (100) MgO single crystal substrate were investigated by Auger electron spectroscopy (AES). A diffusion of Mg from the substrate into the whole thickness (400nm) of the as-deposited K(Ta_0.65Nb_0.35)O₃ films was observed with an accumulation of Mg at the surface. Ex situ post-annealing (750°C/2h) has led to a homogeneous distribution of Mg in all the ferroelectric coating. This strong reaction between film and substrate promotes a doping effect, responsible for the reduction of K(Ta_0.65Nb_0.35)O₃ dielectric losses in comparison with films grown on other substrates.

Keywords: Potassium tantalate niobate; KTN; PLD; AES; Mg diffusion; Dielectric losses

Electron transfer behavior at polyoxometalate-adsorbed alkanethiol self-assembled monolayers by Yeonyi Chu; Jandee Kim; Suhee Choi; Choong Kyun Rhee; Jongwon Kim (pp. 9490-9497).

► Polyoxometalate ions adsorb on the surface of alkanethiol self-assembled monolayers. ► POM adsorption on SAM forms a composite organic–inorganic hybrid layer. ► The electron transfer behavior at SAM can be controlled by the adsorption of POM. ► The chain length of SAM and charge of POM controls the electron transfer features.The interaction between polyoxometalate (POM) anions, SiMo₁₂O₄₀⁴⁻, and a self-assembled monolayer (SAM) of dodecanethiol (DT) on Au surfaces was investigated using electrochemical methods, X-ray photoelectron spectroscopy, and scanning probe microscopy. The SiMo₁₂O₄₀⁴⁻ ions adsorb on the SAM of DT on Au to form a composite organic–inorganic hybrid layer. The adsorbed SiMo₁₂O₄₀⁴⁻ ion on the SAM layer shows its characteristic redox waves with an electron transfer rate slower than that on a bare Au electrode. The electron transfer behavior at DT−SAM could be regulated by the adsorption of SiMo₁₂O₄₀⁴⁻ depending on the charge of the investigated electroactive species: a significant increase toward a positively charged Ru(NH₃)₆³⁺ ion, a moderate increase toward a neutral 1,1′-ferrocenedimethanol molecule and a slight decrease toward a negatively charged Fe(CN)₆³⁻ ion. The effect of the chain length of alkanethiols on the adsorption of SiMo₁₂O₄₀⁴⁻ ion was also investigated: as the chain length decreases, the amount of the adsorbed POM increases and the electron transfer rate through the composite layers increases. The nature of SiMo₁₂O₄₀⁴⁻ ions adsorbed on the SAMs of alkanethiols on Au is discussed in detail.

Keywords: Electron transfer; Polyoxometalate; Self-assembled monolayers; Organic–inorganic hybrid layer

Chemical synthesis of nanocrystalline SnO₂ thin films for supercapacitor application by S.N. Pusawale; P.R. Deshmukh; C.D. Lokhande (pp. 9498-9502).

• Nanosize (5nm) SnO₂ thin films have been prepared by chemical synthesis. • The SnO₂ thin films showed highly porous morphology. • A maximum specific capacitance of 66Fg⁻¹ for nanocrystalline SnO₂.Nanocrystalline SnO₂ thin films were deposited by simple and inexpensive chemical route. The films were characterized for their structural, morphological, wettability and electrochemical properties using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy techniques (SEM), transmission electron microscopy (TEM), contact angle measurement, and cyclic voltammetry techniques. The XRD study revealed the deposited films were nanocrystalline with tetragonal rutile structure of SnO₂. The FT-IR studies confirmed the formation of SnO₂ with the characteristic vibrational mode of Sn–O. The SEM studies showed formation of loosely connected agglomerates with average size of 5–10nm as observed from TEM studies. The surface wettability showed the hydrophilic nature of SnO₂ thin film (water contact angle 9°). The SnO₂ showed a maximum specific capacitance of 66Fg⁻¹ in 0.5 Na₂SO₄ electrolyte at 10mVs⁻¹ scan rate.

Keywords: Chemical synthesis; Nanocrystalline SnO; ₂; Thin films; Supercapacitor

Formation mechanism of Si(100) surface morphology in alkaline fluoride solutions by Qingmei Chu; Xiang Liu; Pengxiang Zhang; Yongnian Dai (pp. 9503-9506).

• Different surface morphology are obtained in different alkaline fluoride solutions. • No Si–F bond exists, F⁻ and CO₃²⁻ ions accelerate the condensation of Si–OH groups. • Bare silicon and silicon oxide coexist at the wafer surface during etching process. • Silicon oxides determine surface morphology in alkaline fluoride solution.Formation mechanism of Si(100) surface morphology in alkaline fluoride solutions was investigated both theoretically and experimentally. By analysis of Raman spectra of silicon wafer surfaces and three kinds of etching solutions (NaOH, NaOH/NH₄F, and NaOH/NH₄F/Na₂CO₃) with and without addition of Na₂SiO₃·9H₂O, no Si–F bond is formed, F⁻ and CO₃²⁻ ions accelerate the condensation of Si–OH groups. Based on experimental results, it is proposed that bare silicon and silicon oxide coexist at the wafer surface during etching process and silicon oxide of different structure, size, and site at the surface manufacture different surface morphology in alkaline fluoride solution.

Keywords: Silicon; Etching mechanism; Fluoride solution; Raman spectroscopy; Alkaline

Effect of fabrication parameters on morphological and optical properties of highly doped p-porous silicon by Maryam Zare; Abbas Shokrollahi; Faramarz E. Seraji (pp. 9507-9514).

► The porosity of the PS layers becomes more when applied current density (J) is increased. ► The layer thickness in 25% and 20% HF is in the micrometer range and it improves with increasing time. ► Decline in [HF] causes a decrease in the roughness of the surface and mean height of the layer. ► The rms roughness of OPS is less than 0.87nm, shows a smooth and uniform surface after oxidation. ► R in sample with higher [HF] is more. In similar samples, higher J causes greater R in visible range.Porous silicon (PS) layers were fabricated by anodization of low resistive (highly doped) p-type silicon in HF/ethanol solution, by varying current density, etching time and HF concentration. Atomic force microscopy (AFM) and field emission scanning electron microscope (FESEM) analyses were used to investigate the physical properties and reflection spectrum was used to investigate the optical behavior of PS layers in different fabrication conditions. Vertically aligned mesoporous morphology is observed in fabricated films and with HF concentration higher than 20%. The dependence of porosity, layer thickness and rms roughness of the PS layer on current density, etching time and composition of electrolyte is also observed in obtained results. Correlation between reflectivity and fabrication parameters was also explored. Thermal oxidation was performed on some mesoporous layers that resulted in changes of surface roughness, mean height and reflectivity of the layers.

Keywords: Porous silicon; Electrochemical; Mesoporous; FESEM; AFM; Reflectivity

Synthesis and characterization of Cr doped CdS nanoparticles stabilized with polyvinylpyrrolidone by K. Siva Kumar; A. Divya; P. Sreedhara Reddy (pp. 9515-9518).

► Cr doped CdS nanoparticles were synthesized by chemical co-precipitation method using PVP as surfactant. ► The influence of Cr content on the physical properties of Cr doped CdS nanoparticles were investigated. ► The synthetic route could be adopted for producing high-quality gram scale synthesis of doped semiconductor nanoparticles.Undoped and Cr (2 and 4at.%) doped CdS nanoparticles were synthesized in aqueous solution by simple chemical co-precipitation method using polyvinylpyrrolidone (PVP) as stabilizer. The prepared nanoparticles were examined using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDAX), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (DRS) and Fourier transform infrared spectroscopy (FTIR). XRD pattern of the nanoparticles showed cubic zincblende phase with the particle size of the order of 3–4nm, which was in good agreement with the results obtained from TEM studies. The EDAX analysis confirmed that Cd, Cr and S elements were present in the samples and the variations between the target and actual compositions were microscopic. UV–vis DRS spectra of the samples exhibited decrease in the band gap which further attests the incorporation of Cr into CdS nanoparticles. FTIR studies revealed that the undoped as well as Cr doped CdS nanoparticles were capped by polyvinylpyrrolidone.

Keywords: CdS; Nanoparticles; Transmission electron microscopy (TEM); Fourier transform infrared spectroscopy (FTIR)

Soot capture and combustion for perovskite La–Mn–O based catalysts coated on honeycomb ceramic in practical diesel exhaust by Lei Li; Xiangqian Shen; Pan Wang; Xianfeng Meng; Fuzhan Song (pp. 9519-9524).

Display Omitted► Nanosized perovskite La–Mn–O based oxides coated honeycomb ceramic was obtained. ► Catalytic performance of nanosized perovskite oxides was examined by TG analysis. ► Smoke opacity was measured for coated catalysts in diesel exhaust gas emissions. ► The catalytic performance is influenced by composition, pore structure, etc.Nanosized perovskite oxides of LaMnO₃, La_0.8K_0.2MnO₃ and La_0.8K_0.2Co_0.5Mn_0.5O₃ with grain sizes about 16–28nm were prepared by the citrate–gel process and their coatings with thickness about 30μm and a coherent interface between the coating and the honeycomb ceramic were obtained by the sol–gel assisted dip-coating technique. The powders and coatings were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The specific surface area was measured by the Brunauere–Emmette–Teller method. The catalytic performance was evaluated by thermo-gravimetric analysis under model conditions and by the smoke opacity measurement for the practical exhaust gas emissions at 200–400°C, respectively. The results show that all three perovskite oxide catalysts have a capture effect of soot and a catalytic activity for soot combustion. The capture effect is mainly related to the porous structural characteristic of the catalyst and the catalytic performance for soot combustion is largely affected by the chemical composition, grain size, specific surface area and pore structure, which are related to the ions substitution and calcination temperature. Among these three catalysts, La_0.8K_0.2MnO₃ shows the best comprehensive catalytic performance and the La_0.8K_0.2MnO₃ coated honeycomb ceramic will be a promising device for diesel exhaust gas emissions.

Keywords: Lanthanum manganese oxide; Diesel exhaust; Soot; Catalyst; Sol–gel; Coating

Tuning the hydrophobicity of ZSM-5 zeolites by surface silanization using alkyltrichlorosilane by Xiaolong Han; Lei Wang; Jiding Li; Xia Zhan; Jian Chen; Jichu Yang (pp. 9525-9531).

► ZSM-5 zeolites with different hydrophobicity were obtained by chlorosilanes modification. ► With increasing the alkyl chain length of trichlorosilane, the hydrophobicity increased. ► With an increase in the pre-treatment temperature, the hydrophobicity decreased. ► The modified ZSM-5 particles possessed good hydrophobicity at a temperature below 250°C in air.ZSM-5 zeolites were modified with alkyltrichlorosilanes of various chain lengths (octyltrichlorosilane, decyltrichlorosilane, dodecyltrichlorosilane and hexadecyltrichlorosilane) and characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Thermal gravimetric analysis (TGA) and contact angle measurements (CA). The results showed that a closely packed and hydrophobic layer was presented at the particles surface and the surface wetting property varied from hydrophilic to hydrophobic, even to superhydrophobic. It was interesting to notice that the hydrophobic properties of modified ZSM-5 particles could be tuned by varying the chain length of chlorosilane and changing the pretreatment temperature before silanization. With increasing the alkyl chain length of trichlorosilane, the hydrophobicity increased. However, with an increase in the pretreatment temperature, the hydrophobicity decreased. Moreover, the relationship between the wetting properties and thermal stability was also investigated, the results showed that the modified ZSM-5 particles possessed good hydrophobicity at a temperature below 250°C in air. These modified ZSM-5 particles may be utilized for many potential applications, such as membrane fillers, selective adsorbents, catalysts, chromatographic supports and so on.

Keywords: Surface modification; ZSM-5; Alkyltrichlorosilane; Superhydrophobicity

Cold flame-sprayed and oil-impregnated porous metallic coatings by G. Kalácska; L. Fazekas; R. Keresztes; A. Tóth; J. Szépvölgyi (pp. 9532-9538).

► The surface composition of the flame-sprayed coatings differs from that of the bulk, since the surface is depleted in Fe and enriched in B, C and Si. The alloy-forming metals are present on the coatings mainly in oxidised and hydroxidised states. ► Oil uptake and release are inversely related to the oxygen concentration at the surface of the coatings. ► The surface energy is dominated by the Lifshitz-van der Waals component of surface energy. ► Oil uptake and release are inversely related to the Lifshitz-van der Waals component of surface energy.Porous metallic coatings were prepared from three commercial alloy powders on 16MnCr5 steel by cold flame spraying. The mechanical characterisation of the coatings was performed by Vickers microindentation and debonding tests. Porosity was determined by image analysis of the optical micrographs of the polished cross-sections. The coatings were impregnated with motor oil 15W40 with the aim of preparing a lubricating system. The amounts of oil uptake and release by the coatings were determined under controlled conditions. The surfaces of the coatings were examined by X-ray photoelectron spectroscopy (XPS) and wettability studies. The amounts of oil uptake and release showed inverse relationship with the oxygen concentration at the surface and also with the Lifshitz-van der Waals component of surface energy. These relationships offer the possibility of controlling the lubrication properties of cold flame-sprayed and oil-impregnated porous metallic coatings.

Keywords: Cold flame spray; Porous coating; Oil impregnation

Lactic acid aided electrochemical deposition of c-axis preferred orientation of zinc oxide thin films: Structural and morphological features by Thou-Jen Whang; Mu-Tao Hsieh; Jia-Ming Tsai; Shyan-Jer Lee (pp. 9539-9545).

► Lactic acid improves the electrodeposition of c-axis preferred orientation of ZnO films. ► High transmittance in visible light range with a sharp edge below band gap of the ZnO films attained. ► Concentration of zinc nitrate and deposition potential significantly affect the growth direction and crystal diameter of zinc oxide.Compact and homogeneous c-axis preferred orientation of zinc oxide (ZnO) films on indium tin oxide (ITO) coated glass have been prepared electrochemically at −1.2V vs. Ag|AgCl in a weak acidic condition from 0.06M Zn(NO₃)₂ with 3mM lactic acid (LA) added. LA was found having strong influence on the electrodeposition of c-axis preferred orientation of zinc oxide films. Other experimental variables such as deposition temperature, potential, and precursor concentration were also conducted in this article. Among these variables, it was found that precursor concentration of zinc nitrate influenced significantly on growth direction and crystal diameter of zinc oxide. Cyclic voltammetry was used to observe the electrochemistry of the deposition. Crystallinities of the films were examined by X-ray diffractometer. The morphologies of zinc oxide films were observed with a field emitting scanning electron microscope. Optical characteristics of zinc oxide layers were measured with UV–vis spectrophotometer. The band gap of the deposited zinc oxide thin films was evaluated from the Tauc relationship of ( αhν)² vs. hν, which was found to be 3.31eV.

Keywords: Zinc oxide; Lactic acid; Electrochemical deposition; Thin films

CTAB assisted growth and characterization of nanocrystalline CuO films by ultrasonic spray pyrolysis technique by Iqbal Singh; Gursharan Kaur; R.K. Bedi (pp. 9546-9554).

Display Omitted► Effect of CTAB on the structural and morphological properties of CuO films. ► CTAB assisted CuO films show an increase in activation energy of conduction. ► CTAB doped CuO films show good sensitivity for NH₃ at room temperature. ► Two adsorption models used for exploring the kinetics of sensing mechanism.An aqueous solution of cupric nitrate trihydrate (Cu(NO₃)₂·3H₂O) modified with cetyltrimetylammonium bromide (CTAB) is used to deposit CuO films on glass substrate by chemical spray pyrolysis technique. The thermal analysis shows that the dried CTAB doped precursor decomposes by an exothermic reaction and suggests that minimum substrate temperature for film deposition should be greater than 270°C. X-ray diffraction (XRD) studies indicate the formation of monoclinic CuO with preferential orientation along (002) plane for all film samples. The CTAB used as cationic surfactant in precursor results in the suppression of grain growth in films along the (110), (020) and (220) crystal planes of CuO. Surfactant modified films showed an increase in crystallite size of 14nm at substrate temperature of 300°C. The scanning electron micrographs (FESEM) confirm the uniform distribution of facets like grains on the entire area of substrate. CTAB modified films show a significant reduction in the particle agglomeration. Electrical studies of the CuO films deposited at substrate temperature of 300°C with and without surfactant reveal that the CTAB doping increase the activation energy of conduction by 0.217eV and room temperature response to ammonia by 9%. The kinetics of the ammonia gas adsorption on the film surface follows the Elovich and Diffusion models.

Keywords: Cationic surfactants; Spray pyrolysis; Sensor

Preparation of silicate tungsten bronzes on aluminum by plasma electrolytic oxidation process in 12-tungstosilicic acid by M. Petković; S. Stojadinović; R. Vasilić; I. Belča; Z. Nedić; B. Kasalica; U.B. Mioč (pp. 9555-9561).

► Percentage of oxide coatings area covered by active discharge sites decreases with time. ► Spatial density of microdischarges is the highest in the early stage of PEO process. ► Oxide coating is partly crystallized and mainly composed of γ-Al₂O₃ and WO₃. ► Outer layer of the coating is silicate tungsten bronze.The growth of silicate tungsten bronzes on aluminum by plasma electrolytic oxidation in 12-tungstosilicic acid is experimentally investigated and discussed. Real time imaging and optical emission spectroscopy characterization of plasma electrolytic oxidation show that spatial density of microdischarges is the highest in the early stage of the process, while the percentage of oxide coating area covered by active discharge sites decreases slowly with time. Emission spectrum of microdischarges has several intensive band peaks originating either from aluminum electrode or from the electrolyte. Surface roughness of obtained oxide coatings increases with prolonged time of plasma electrolytic oxidation, as their microhardness decreases. Raman spectroscopy and energy dispersive X-ray spectroscopy are employed to confirm that the outer layer of oxide coatings formed during the plasma electrolytic oxidation process is silicate tungsten bronzes.

Keywords: Plasma electrolytic oxidation (PEO); 12-Tungstosilicic acid; Silicate tungsten bronzes

Improvement of surface wettability and interfacial adhesion of poly-(p-phenylene terephthalamide) by incorporation of the polyamide benzimidazole segment by Ren-Qin Cai; Tao Peng; Feng-De Wang; Guang-Dou Ye; Jian-Jun Xu (pp. 9562-9567).

► The surface features of Kevlar-49 fiber and DAFIII and their effect on the fiber/matrix inter-phase adhesion, which are rarely reported in the literature. ► The surface of DAFIII has more polar functional groups contents, larger roughness and higher surface free energy than that of Kevlar-49 fiber. ► The interfacial shear strength (IFSS) of DAFIII/matrix composite is 25.7% higher than that of Kevlar-49/matrix composite. ► The surface feature play an important role in bonding and mechanical interlocking of the fiber and matrix.In order to investigate the effect of the polyamide benzimidazole group on the surface wettability and interfacial adhesion of fiber/matrix composites, surface features of two kinds of aramid fibers, poly (p-phenylene terephthalamide) fiber (Kevlar-49) and poly-(polyamide benzimidazole-co-p-phenylene terephthalamide) (DAFIII), have been analyzed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and contact angle analysis (CAA) system, respectively.The results show that with the incorporation of the polyamide benzimidazole segment, more polar functional groups exist on DAFIII surface. The contact angles of water and diiodomethane on DAFIII surface get smaller. The surface free energy of DAFIII increases to 36.5mJ/m², which is 2.3% higher than that of Kevlar-49. In addition, DAFIII has a larger rough surface compared with that of Kevlar-49 due to different spinning processes. The interfacial shear strength (IFSS) of DAFIII/matrix composite is 25.7% higher than that of Kevlar-49/matrix composite, in agreement with the observed results from surface feature tests. SEM micrographs of failed micro-droplet specimens reveal a strong correlation between the fracture features and the observed test data.

Keywords: Aramid fibers; Surface wettability; XPS; Interfacial shear strength

Structural and optical properties of RF magnetron sputtered aluminum nitride films without external substrate heating by Atul Vir Singh; Sudhir Chandra; A.K. Srivastava; B.R. Chakroborty; G. Sehgal; M.K. Dalai; G. Bose (pp. 9568-9573).

► Highly c-axis oriented AlN films without external substrate heating. ► Independence of preferred (002) orientation on sputtering pressure. ► Nano-crystallites with absence of any interface porosity and amorphous structure. ► Elemental composition uniformity of the film with depth. ► No extra control mechanism as required in reactive sputtering.We report structural and optical properties of aluminum nitride (AlN) thin films prepared by RF magnetron sputtering. A ceramic AlN target was used to sputter deposit AlN films without external substrate heating in Ar–N₂ (1:1) ambient. The X-ray diffraction and high resolution transmission electron microscopy results revealed that the films were preferentially oriented along c-axis. Cross-sectional imaging revealed columnar growth perpendicular to the substrate. The secondary ion mass spectroscopy analysis confirmed that aluminum and nitrogen distribution was uniform within the thickness of the film. The optical band gap of 5.3eV was evaluated by UV–vis spectroscopy. Photo-luminescence broad band was observed in the range of 420–600nm with two maxima, centered at 433nm and 466nm wavelengths related to the energy states originated during the film growth. A structural property correlation has been carried out to explore the possible application of such important well oriented nano-structured two-dimensional semiconducting objects.

Keywords: Aluminum nitride film; RF magnetron sputtering; X-ray diffraction; High resolution transmission electron microscopy; Secondary ion mass spectroscopy; Optical properties

Rapid synthesis and luminescence of the Eu³⁺, Er³⁺ codoped ZnO quantum-dot chain via chemical precipitation method by Jihui Lang; Xue Li; Jinghai Yang; Lili Yang; Yongjun Zhang; Yongsheng Yan; Qiang Han; Maobin Wei; Ming Gao; Xiaoyan Liu; Rui Wang (pp. 9574-9577).

► ZnO quantum-dot chains codoped with Eu³⁺ and Er³⁺ are synthesized. ► Green emissions of Er³⁺ are attributed to²H_11/2→⁴I_15/2 and⁴S_3/2→⁴I_15/2 transitions. ► Red emissions of Eu³⁺ are attributed to⁵D₀→⁷F₁ and⁵D₀→⁷F₂ transitions. ► The doping concentration of Er³⁺ ions influences the red emission of Eu³⁺ ions.ZnO quantum-dot chains codoped with Eu³⁺ and Er³⁺ were synthesized by the chemical precipitation method and the codoping effects on the structures, morphologies and optical properties of the powders were briefly investigated. The X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) results indicated the Eu³⁺ and Er³⁺ were incorporated into the crystal lattice of ZnO host. Transmission electron microscope (TEM) measurements showed the sizes of the ZnO quantum dots decreased with the increase of Eu³⁺ and Er³⁺ doping concentration, and the quantum-dot chains were formed by codoping with Eu³⁺ and Er³⁺. The green emissions in the photoluminescence spectra were attributed to 4f–4f of Er³⁺ inner shell²H_11/2→⁴I_15/2 and⁴S_3/2→⁴I_15/2 transitions, and the characteristic red emissions of Eu³⁺ ions were attributed to the⁵D₀→⁷F₁ and⁵D₀→⁷F₂ transitions, respectively. Moreover, the red emission of the Eu³⁺ ions gradually decreased with the Er³⁺ ions doping concentration increased, which may be due to the different energy storage centers in the powders.

Keywords: ZnO quantum-dot chain; Chemical precipitation method; Rare ions; Photoluminescence

Photoluminescence of Si from Si nanocrystal-doped SiO₂/Si multilayered sample by Yong Ren; Yong-Bin Chen; Miao Zhang; Jiang Zhu; Xing-Wang Zhang; You-Yuan Zhao; Ming Lu (pp. 9578-9582).

► It presents a systematic study of PL emission of Si nanocrystals from Si/SiO multilayered structures. ► The result shows that the PL intensity is determined by both the amount of doping of Si and the distribution of Si as well. ► Also it shows that the PL intensity of Si nanocrystals from the multilayered structure can be significantly greater than the sample prepared by co-evaporation of Si and SiO at the same optimized Si to O ratio.A multilayered Si nanocrystal-doped SiO₂/Si (or Si-nc:SiO₂/Si) sample structure is studied to acquire strong photoluminescence (PL) emission of Si via modulating excess Si concentration. The Si-nc:SiO₂ results from SiO thin film after thermal annealing. The total thickness of SiO layer remains 150nm, and is partitioned equally into a number of sublayers ( N=3, 5, 10, or 30) by Si interlayers. For each N-layered sample, a maximal PL intensity of Si can be obtained via optimizing the thickness of Si interlayer (or d_Si). This maximal PL intensity varies with N, but the ratio of Si to O is nearly a constant. The brightest sample is found to be that of N=10 and d_Si=1nm, whose PL intensity is ∼5 times that of N=1 without additional Si doping, and ∼2.5 times that of Si-nc:SiO₂ prepared by co-evaporating of SiO and Si at the same optimized ratio of Si to O. Discussions are made based on PL, TEM, EDX and reflectance measurements.

Keywords: PACS; 78.55.−m; 78.67.Bf; 81.07.BcSi nanocrystal; Photoluminescence; Multilayer

Investigation on microstructure and properties of CrAlN/AlON nanomultilayers by Kangpei Zheng; Ping Liu; Wei Li; Fengcang Ma; Xinkuan Liu; Xiaohong Chen (pp. 9583-9586).

► CrAlN/AlON nanomultilayers were synthesized and investigated by XRD, HRTEM and nano-indentation first time. ► Under the template effect of NaCl structural CrAlN layers, amorphous AlON was forced to crystallize and grew epitaxially with CrAlN layers. ► The maximum hardness could reach 34.7GPa when AlON layer thickness was 0.9nm and the strengthen mechanism was explained.Artificially modulated CrAlN/AlON nanomultilayers were synthesized by direct current reactive magnetron sputtering. The microstructure and mechanical properties were evaluated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and nano-indentation techniques. The crystallization of AlON layer and its influence on the mechanical property of the nanomultilayers were studied. The results revealed that, under the template effect of NaCl structural CrAlN layer, amorphous AlON was forced to crystallize and grew epitaxially with CrAlN layer when AlON layer thickness was below 0.9nm, leading to an increase of hardness up to 32.8GPa. With the further increase of the AlON layer thickness, AlON layer gradually transformed into amorphous structure and blocked epitaxial growth of the multilayers, resulting in the decrease of hardness. The effect of CrAlN layer thickness on hardness of CrAlN/AlON nanomultilayers was also investigated. With the decrease of CrAlN layer thickness, the hardness increased gradually. The maximum hardness was 34.7GPa when CrAlN layer thickness of was 3.0nm. The strengthen mechanism of CrAlN/AlON nanomultilayers was finally discussed.

Keywords: Superhardness effect; CrAlN/AlON nanomultilayers; Epitaxial growth; Amorphous crystallization

Combined XPS and contact angle studies of ethylene vinyl acetate and polyvinyl acetate blends by I.O. Ucar; M.D. Doganci; C.E. Cansoy; H.Y. Erbil; I. Avramova; S. Suzer (pp. 9587-9594).

.Display Omitted► Surface properties of dip coated blends of EVA-33 with PVAc were investigated. ► Control of surface pattern protrusion size was achieved for PVAc/EVA-33 blends. ► XPS shoved a linear relation between VA content on the surface and in the bulk. ► A good agreement was found between basic surface free energy and oxygen content. ► Deviations from Cassie–Baxter equation were discussed depending on VA content.In this study, we prepared thin films by blending ethylene vinyl acetate copolymers (EVA) containing 12–33(wt.%) vinyl acetate (VA) with polyvinyl acetate (PVAc) and high density polyethylene homopolymers. Large area micropatterns having controlled protrusion sizes were obtained by phase-separation especially for the PVAc/EVA-33 blends using dip coating. These surfaces were characterized by XPS and contact angle measurements. A reasonably linear relation was found between the VA content on the surface (wt.%) obtained from XPS analysis and the VA content in bulk especially for PVAc/EVA-33 blend surfaces. PE segments were more enriched on the surface than that of the bulk for pure EVA copolymer surfaces similar to previous reports and VA enrichment was found on the EVA/HDPE blend surfaces due to high molecular weight of HDPE. Waterθe decreased with the increase in the VA content on the blend surface due to the polarity of VA. A good agreement was obtained betweenγs− and atomic oxygen surface concentration with the increase of VA content. The applicability of Cassie–Baxter equation was tested and found that it gave consistent results with the experimental water contact angles for the case where VA content was lower than 55wt.% in the bulk composition.

Keywords: Ethylene vinyl acetate copolymers; Polymer blending; Surface free energy; XPS; Contact angle; Polyolefin

High-performance UV detector based on Ga-doped zinc oxide thin films by S.S. Shinde; K.Y. Rajpure (pp. 9595-9599).

► Fabrication of photoconductive UV detector by using spray pyrolysis. ► Photoconductive UV detector based on Ga-doped ZnO thin films having MSM configuration. ► I– V characteristic, spectral and transient response of Ga-doped ZnO photodetector. ► Highest responsivity of about 1125A/W at 5V bias.High-quality ultraviolet photoconductive detectors have been fabricated using Ga-doped zinc oxide layers grown by spray pyrolysis on glass substrates. The performance of the photoconductivity has been tested by the measurements of the current–voltage ( I– V) characteristics under forward and reverse bias. The devices have been characterized to investigate the effect of buffer layer on the detector performances. The behaviour of photocurrent with respect to optical power density, wavelength and chopping time has been investigated. We achieved the highest responsivity of about 1125A/W at 5V bias at 365nm peak wavelength. Our approach provides a simple and cost-effective way to fabricate high-performance ‘visible-blind’ UV detectors.

Keywords: Ultraviolet photodetector; Ga:ZnO; Buffer layer; Spray pyrolysis

Lead-free ferroelectric BaTiO₃ doped-(Na_0.5Bi_0.5)TiO₃ thin films processed by pulsed laser deposition technique by Cristina Dragoi; Marin Cernea; Lucian Trupina (pp. 9600-9605).

► MPB lead free BNT–BT_0.08 thin films were deposited on Pt/Si substrate, in optimized pulsed laser deposition conditions. ► Structural and morphological characteristics have been correlated with deposition process and target morphology. ► The BNT–BT_0.08 thin film exhibits a well-defined ferroelectric hysteresis loop at room temperature. ► The leakage current density in BNT–BT_0.08 thin film is relatively low. ► Local piezoelectric and ferroelectric responses in BNT–BT_0.08 thin films, were identified.The difficulties in synthesizing phase pure BaTiO₃ doped-(Na_0.5Bi_0.5)TiO₃ are known. In this work, we reporting the optimized pulsed laser deposition (PLD) conditions for obtaining pure phase 0.92(Na_0.5Bi_0.5)TiO₃–0.08BaTiO₃, (BNT–BT_0.08), thin films. Dielectric, ferroelectric and piezoelectric properties of BNT–BT_0.08, thin films deposited by PLD on Pt/TiO₂/SiO₂/Si substrates are investigated in this paper. Perovskite structure of BNT–BT_0.08 thin films with random orientation of nanocrystallites has been obtained by deposition at 600°C. The relative dielectric constant and loss tangent at 100kHz, of BNT–BT_0.08 thin film with 530nm thickness, were 820 and 0.13, respectively. Ferroelectric hysteresis measurements indicated a remnant polarization value of 22μC/cm² and a coercive field of 120kV/cm. The piezoresponse force microscopy (PFM) data showed that most of the grains seem to be constituted of single ferroelectric domain. The as-deposited BNT–BT_0.08 thin film is ferroelectric at the nanoscale level and piezoelectric.

Keywords: Lead-free ferroelectrics; Thin films; Pulsed laser deposition; Dielectric and piezoelectric properties

Electrochromic and electrochemical properties of amorphous porous nickel hydroxide thin films by A.I. Inamdar; A.C. Sonavane; S.M. Pawar; YoungSam Kim; J.H. Kim; P.S. Patil; Woong Jung; Hyunsik Im; Dae-Young Kim; Hyungsang Kim (pp. 9606-9611).

► We examined the porosity effect on electrochromic properties of nickel hydroxide. ► CBD is of interest due to its low cost, environmental friendliness. ► Exclusive analysis on XPS measurements of nickel hydroxide samples is presented. ► Improved optical densities and response time (ms) of the samples have been obtained. ► The measured colouration efficiency ranges between 30-40cm²/C.Nickel hydroxide films were prepared using the chemical bath deposition (CBD) technique. The amorphous nature of the films was confirmed by X-ray diffraction measurements. X-ray photoelectron spectroscopy (XPS) measurements showed that the films exhibited nickel hydroxide nature. The porosity of the films was studied using optical measurements. The electrochromic properties of the porous nickel hydroxide layers were investigated, using cyclic voltammetry, chronoamperometry, in situ transmittance, UV–vis spectroscopy, and impedance spectroscopy. The change in the optical density (ΔOD) was found to be 0.79 for the as-deposited nickel hydroxide films, whereas it is 0.53 and 0.50 for the films annealed at 150°C and 200°C, respectively. The in situ transmittance and chronoamperometry curves revealed that the annealed films had a very fast colouration ( t_c<290ms) and decolouration ( t_b<130ms). The measured colouration efficiencies range between 30 and 40cm²/C. The impedance measurements revealed the faster colouration and good electrochromic properties for the annealed nickel hydroxide films.

Keywords: Nickel hydroxide; Electrochromism; Cyclic voltammetry; Chronoamperometry; UV–vis spectroscopy; Impedance spectroscopy

Anti-reflective and hydrophobic surface of self-organized GaN nano-flowers by S. Dhamodaran; D. Sathish Chander; J. Ramkumar (pp. 9612-9615).

► Self-assembled GaN nano-flowers growth using a simple CVD reactor is reported. ► Catalysis-free GaN nano-flowers using CVD is not reported elsewhere. ► Reflectance as low as 5% in comparison to 25% from GaN templates has been recorded. ► Hydrophobic surface with 145° contact angle useful for nano-fluidic devices.GaN nano flowers were grown on various commercial substrates by a simple catalyst free chemical vapor deposition (CVD) technique. The size and shape of the nanostructures were characterized by scanning electron microscopy (SEM). The influence of the substrate, growth temperature, and ammonia flow rate on the size and shape of the nano-flowers were investigated along with their anti-reflective and hydrophobic properties. The normal incident reflectivity measurements carried out on the nano structures showed very low (5%) reflectivity. The wettability of the surface investigated by the static contact angle of water droplet revealed their hydrophobic nature with a large contact angle of about 145°. These results on catalysis-free nanostructures would be useful for anti-reflective surfaces/coatings in solar cell applications.

Keywords: GaN; Nano-flowers; Anti-reflective; Hydrophobic

Improving the conductivity of diamond-like carbon films with zinc doping and its material properties by H. Wong; Y.M. Foong; D.H.C. Chua (pp. 9616-9620).

► Highly resistive diamond-like films can have a significant increase in its conductivity through the incorporation (or doping) of Zn into the amorphous film. ► Incorporation of Zn increases the critical load while maintaining similar coefficient of friction to that of pure diamond-like carbon films. ► This is the first report of Zn incorporation into diamond-like carbon films based on literature review with some unique findings. ► The growth mechanism and possible reasons were given why this phenomenon is observed for Zn but not previously observed when other metals were used.Zinc doped diamond-like carbon (DLC) nanocomposite thin films are fabricated by KrF pulsed laser deposition. Carbon targets containing 3.0, 5.0 and 10.0 atomic percentages of zinc are used as the source for the laser system. Investigation of electrical properties by the four-point probe shows that doping zinc into DLC can lower the electrical sheet resistivity. Microstructural analysis by Raman spectroscopy and XPS show a lower sp³ content but a higher SiC content with an increasing amount of zinc incorporation. The increase of SiC leads to an increase in adhesion strength. Surface roughness of the films also increases while the coefficients of friction for the films do not change.

Keywords: Diamond-like carbon films; Zinc doped DLC nanocomposite; Microstructure; Tribological properties; Electrical properties

Novel fabrication of net-like and flake-like Fe doped TiO₂ thin films by Fujian Ren; Kai He; Yunhan Ling; Jiayou Feng (pp. 9621-9625).

► Novel fabrication of net-like and flake-like pure TiO₂ and Fe–TiO₂ thin films. ► Fe ions concentration determines the surface morphology after chemical treatment. ► Net-like morphology with low Fe dopant, while a flake-like one when Fe exceeds 1.7at.%. ► Significant visible light response after Fe doping.New morphologies of net-like and flake-like TiO₂ thin films with different concentrations of Fe dopant were successfully fabricated by micro-arc oxidation (MAO) process of Ti plates and a subsequent chemical treatment of the as-prepared MAO-TiO₂ thin films. It was found that Fe ions can be easily introduced into the MAO-TiO₂ samples with the increase concentration of K₄(FeCN)₆·3H₂O precursor, and the amount of Fe determined the morphologies of TiO₂ thin films after chemical treatment; net-like morphology was observed with low Fe dopant, while it transformed to a flake-like one when Fe exceeds 1.7at.%. UV–vis spectroscopy test showed that the absorption edge of the Fe ions doped TiO₂ thin films with new morphologies has an obvious red shift.

Keywords: Surface; Nanocrystalline materials; Thin films; Fe dopant; TiO; ₂

Copper-induced crystallization of sputtered silicon on ZnO:Al substrate and the textured interface for light trapping by Yong Zhao; Jian Wang; Qiang Hu; Dan Zhu; Dejie Li (pp. 9626-9630).

► Obtained well crystallized poly-Si by Cu-induced crystallization on AZO substrate. ► Poly-Si quality is improved by the introduction of O₂ when preparing AZO substrate. ► 660nm textured Si with 17.7% average reflectivity, only 45% of the flat Si film.Copper-induced crystallization of a-Si on ZnO:Al (AZO) substrate is studied. On Ar sputtered AZO substrate, the optimized crystallite and crystalline ratio of poly-Si are ∼30nm and ∼71%, respectively. O₂ is also introduced and optimized when preparing AZO substrates. On AZO substrate with O₂/Ar+O₂=3%, the crystallite and crystalline ratio of poly-Si are greatly improved, showing ∼40nm and ∼82%, respectively. Textured AZO is prepared for analyzing the light-trapping efficiency. With 40s etching in 0.5% HCl, ∼0.7μm lateral scale and ∼119nm root mean square roughness is obtained. The scattering property is verified by the flat step over a large angle range in the angular distribution measurement. 660nm Cu-induced poly-Si on this AZO substrate shows an average reflectivity of ∼17.7%, only 45% of the flat Si, showing a good light-trapping efficiency and a potential use in solar cells.

Keywords: Cu-induced crystallization; Polycrystalline silicon; Textured ZnO:Al; Light trapping

New insights on contact angle/roughness dependence on high surface energy materials by S. Giljean; M. Bigerelle; K. Anselme; H. Haidara (pp. 9631-9638).

Display Omitted► Micro-roughened isotropic 2D surface with heterogeneous vertical distribution. ► Contact angle measured on high surface energy material in the two liquid phase method. ► Cleaning efficiency has a critical influence on roughness dependent wetting regimes. ► Peak-to-valley amplitudes can account for wetting regimes in place of surface ratios.The relationship between wettability and roughness has been studied on micro-roughened titanium surface after different cleaning procedures. Whereas most studies addressing (super)-hydrophobic behaviors have so far dealt with the wetting of low surface energy and textured substrates in air environment, we here report on a totally novel system and configuration involving the wetting of highly hydrophilic, textured metallic materials in liquid alkane medium, the so-called two liquid phase method. Roughness characterization showed that substrates were isotropic (2D), at a lengthscale much smaller than the size of the drop, with a heterogeneous (vertical) distribution of peaks and valleys. Depending on whether the alkane that initially penetrates and resides in the pores is displaced or not by the water drop (as for air pockets in air environment), we show that different wetting regimes may appear, depending on the cleaning procedure. To our knowledge, this is the first systematic study dealing with the interplay between surface roughness, the wetting behavior and in particular the (super)-hydrophilicity of high surface energy substrates, in non water miscible liquid environments. Whenever competitive processes of liquid/liquid displacement are involved at such high surface energy and textured substrates, such as titanium implant in bone tissue, these results may contribute understanding and predicting their wetting behavior.

Keywords: Wetting regimes; Roughness; Scale effects; High surface energy materials; Two liquid phase method

Effect of the heat treatment on the infrared emissivity of indium tin oxide (ITO) films by Kewei Sun; Wancheng Zhou; Xiufeng Tang; Zhibin Huang; Fa Lou; Dongmei Zhu (pp. 9639-9642).

► Direct current magnetron sputtering was adapted to prepare the 600nm ITO films under different substrate temperatures. ► The mean infrared emissivity was measured in the heat-treatment process of heating and cooling from room temperature to 350°C. ► Effect of the heat treatment on the infrared emissivity of indium tin oxide (ITO) films was investigated in detail. ► The emissivities of all films are below 0.3 in the whole heat treatment process.Indium tin oxide (ITO) films were deposited on glass substrates at temperatures ranging from 100°C to 400°C by direct current magnetron sputtering. The mean infrared emissivities at the waveband of 8–14μm were measured in process of heating and cooling between room temperature and 350°C. Microstructure and phases of ITO films before (Group A) and after (Group B) heat treatment were characterized by SEM and XRD, respectively. Electrical properties were characterized with a four-point probe method and by Hall measurement system. During heat treatment, the infrared emissivity of the film increases with the increase of temperature, and decreases with the decrease of temperature. While, the infrared emissivity of the films decreases slightly around 250°C in heating process. On the other hand, after heat treatment, the crystalline phases of the films have no obvious change. However, both the resistivity and the infrared emissivity of all films decrease.

Keywords: Indium tin oxide films; Direct current magnetron sputtering; Infrared emissivity; Heat treatment

Preparation and characterization of the electrodeposited Cr–Al₂O₃/SiC composite coating by Jifeng Gao; Jinping Suo (pp. 9643-9648).

► SiC content reaches up to 2.5wt% in codeposition of Cr–Al₂O₃/SiC composite coating. ► Al₂O₃ coated SiC as dispersed particles in Cr plating bath. ► Modification increases zeta potential and favors the deposition of SiC particles. ► Combination of coelectrodeposition and modification of nano ceramic particles.To increase the SiC content in Cr-based coatings, Cr–Al₂O₃/SiC composite coatings were plated in Cr(VI) baths which contained Al₂O₃-coated SiC powders. The Al₂O₃-coated SiC composite particles were synthesized by calcining the precursor prepared by heterogeneous deposition method. The transmission electron microscopy analysis of the particles showed that the nano-SiC particle was packaged by alumina. The zeta potential of the particles collected from the bath was up to +23mV, a favorable condition for the co-deposition of the particles and chromium. Pulse current was used during the electrodeposition. Scanning Electron Microscopy (SEM) indicated that the coating was compact and combined well with the substrate. Energy dispersive X-ray analysis of Cr–Al₂O₃/SiC coatings demonstrated that the concentration of SiC in the coating reached about 2.5wt.%. The corrosion behavior of the composite coating was studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The data obtained suggested that the Al₂O₃/SiC particles significantly enhanced the corrosion resistance of the composite coating in 0.05M HCl solution.

Keywords: Coating; Package; Composite coating; Electrodepositon

Enhancement of electron field emission by carbon coating on vertically aligned Si nanowires by N.S. Das; D. Banerjee; K.K. Chattopadhyay (pp. 9649-9653).

► Vertically aligned Si nanowires were synthesized by chemical method. ► Amorphous carbon thin film was coated by DC PECVD. ► Electron field emission performance significantly improved due to amorphous carbon coating.Electron field emission properties of vertically aligned Si nanowires, synthesized by chemically etching p-type Si wafers with different etching times were investigated in detail. Fabrication of Si nanowires was confirmed by field emission scanning electron microscopic investigation. It was observed that a thin layer of amorphous carbon coating over the grown Si nanowires enhanced the field emission properties significantly.

Keywords: PACS; 62.23.Hj; 81.15.-z; 68.37.Vj; 79.70.+qSilicon nanowire; Amorphous carbon coating; FESEM; Field emission

Effect of interface layer on growth behavior of atomic-layer-deposited Ir thin film as novel Cu diffusion barrier by Bum Ho Choi; Jong Ho Lee; Hong Kee Lee; Joo Hyung Kim (pp. 9654-9660).

► Growth and nucleation behavior of Ir films grown by ALD on different interfacial layers were investigated. ► The Ir film grown on the 3-nm-thick TaN surface showed the smoothest and most uniform layer for all the deposition cycles. ► Poor nucleation and three-dimensional island-type growth of the Ir layer were observed on Si, SiO₂, and surface-treated TaN. ► Growth behavior of the Ir layer on different interface layer is related to the chemical bonding pattern of interface layer.Growth and nucleation behavior of Ir films grown by atomic layer deposition (ALD) on different interfacial layers such as SiO₂, surface-treated TaN, and 3-nm-thick TaN were investigated. To grow Ir thin film by ALD, (1,5-cyclooctadiene) (ethylcyclopentadienyl) iridium (Ir(EtCp)(COD)) and oxygen were employed as the metalorganic precursor and reactant, respectively. To obtain optimal deposition conditions, the deposition temperature was varied from 240 to 420°C and the number of deposition cycles was changed from 150 to 300. The Ir film grown on the 3-nm-thick TaN surface showed the smoothest and most uniform layer for all the deposition cycles, whereas poor nucleation and three-dimensional island-type growth of the Ir layer were observed on Si, SiO₂, and surface-treated TaN after fewer number of deposition cycles. The uniformity of the Ir film layer was maintained for all the different substrates up to 300 deposition cycles. Therefore we suggest that the growth behavior of the Ir layer on different interface layer is related to the chemical bonding pattern of the substrate film or interface layer, resulting in better understand the growth mechanism of Ir layer as a copper diffusion barrier. The ALD-grown Ir films show the preferential direction of (111) for all the reflections, which indicates the absence of IrO₂ in metallic Ir.

Keywords: Ir; ALD; Interface; Growth; Mechanism; Cu diffusion barrier

Synthesis of ZnO nanoparticles using surfactant free in-air and microwave method by Deepali Sharma; Sapna Sharma; B.S. Kaith; Jaspreet Rajput; Mohinder Kaur (pp. 9661-9672).

► Synthesis of ZnO nanostructures of different morphologies via surfactant free methods. ► Effective antimicrobial activity of synthesized ZnO nanostructures. ► Photodegradation of methylene blue dye in the presence of ZnO nanoparticles. ► Evaluation of optical properties.Zinc oxide nanoparticles have been successfully prepared by a facile route involving the reaction of zinc sulphate heptahydrate and sodium hydroxide through drop-by-drop mixing synthesis-IA, instant mixing synthesis-IA and under the influence of microwave radiations. The synthesis under different reaction conditions played an important role and led to the formation of zinc oxide nanoparticles of different size and shapes. The synthesized nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The concentration dependent antimicrobial activity of synthesized ZnO nanoparticles was carried out. The photocatalytic activity was evaluated using the photodegradation of methylene blue (MB) dye under UV irradiation. Further, the optical properties of as-prepared ZnO nanoparticles were investigated by UV–vis spectrophotometry. The absence of surfactant led to a simple, cheap and fast method of synthesis of zinc oxide nanoparticles.

Keywords: ZnO nanoparticles; In-air (IA) synthesis; Microwave; Reactive oxygen species (ROS); Photodegradation; Optical property

Thermally switchable thin films of an ABC triblock copolymer of poly( n-butyl methacrylate)-poly(methyl methacrylate)-poly(2-fluoroethyl methacrylate) by Shanju Zhang; Zhan Liu; David G. Bucknall; Lihong He; Kunlun Hong; Jimmy W. Mays; Mark G. Allen (pp. 9673-9677).

► Thin films of the linear block terpolymers show a thermally reversible behavior. ► Thermal switching is driven by the miscibility among the blocks showing UCST and LCST. ► Thin films exhibit lamella-like structures in both UCST and LCST regimes. ► Surface structural changes with temperature are identified.The thermo-responsive behavior of polymer films consisting of novel linear triblock copolymers of poly( n-butyl methacrylate)–poly(methyl methacrylate)–poly(2-fluoroethyl methacrylate) (PnBuMA–PMMA–P2FEMA) are reported using differential scanning calorimetry (DSC), atomic forcing microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contacting angle (CA) measurements. The surface morphology, wettability and chemical structure of thin films of these triblock copolymers on silicon wafers as a function of temperature have been investigated. It has been shown that the wettability of the films is thermally switchable. Detailed structural analysis shows that thermo-responsive surface composition changes are produced. The underlying mechanism of the thermoresponsive behavior is discussed.

Keywords: Block copolymers; Thin films; Stimuli-sensitive polymers; Surface structure; Wettability

Hydrothermal synthesis and ferromagnetism of CuO nanosheets by J.G. Zhao; S.J. Liu; S.H. Yang; S.G. Yang (pp. 9678-9681).

► CuO nanosheets were synthesized through hydrothermal method. ► Ferromagnetism was observed in the CuO nanosheets. ► Ferromagnetism of the CuO nanosheets should come from its nanostructured property.Large quantity of CuO nanosheets was synthesized through hydrothermal method. The samples were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and superconducting quantum interference device. The results showed that the as prepared samples are monoclinic phase CuO with width of about 500nm, length of about 1000nm and thickness of 40–50nm. Magnetic measurements revealed ferromagnetism was existed in the CuO nanosheets. The ferromagnetism could be attributed to the uncompensated spins on the surface of the nanosheets.

Keywords: Hydrothermal synthesis; Nanosheets; Ferromagnetism

Molybdenum thin film deposited by in-line DC magnetron sputtering as a back contact for Cu(In,Ga)Se₂ solar cells by Zhao-Hui Li; Eou-Sik Cho; Sang Jik Kwon (pp. 9682-9688).

► A large area Mo back contact for CIGS thin film solar cells was deposited using in-line DC sputtering system. ► In order to reduce its resistivity and improve the adhesion of Mo film with glass substrate, a bilayer Mo film was deposited. ► The first layer was formed at 12mTorr for better adhesion and the second layer was formed at 3mTorr for lower resistivity.In this paper, we reported the effect of the power and the working pressure on the molybdenum (Mo) films deposited using an in-line direct current (DC) magnetron sputtering system. The electrical and the structural properties of Mo film were improved by increasing DC power from 1 to 3kW. On the other side, the resistivity of the Mo films became higher with the increasing working pressure. However, the adhesion property was improved when the working pressure was higher. In this work, in order to obtain an optimal Mo film as a back metal contact of Cu(In,Ga)Se₂ (CIGS) solar cells, a bilayer Mo film was formed through the different film structures depending on the working pressure. The first layer was formed at a high pressure of 12mTorr for a better adhesion and the second layer was formed at a low pressure of 3mTorr for a lower resistivity.

Keywords: Mo metal back contact; CIGS solar cell; In-line DC sputtering; Sputtering power; Working pressure

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Applied Surface Science (v.257, #22)

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Applied Surface Science (v.257, #22)