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Applied Surface Science (v.254, #20)

Synthesis, characterization and mechanism of cetyltrimethylammonium bromide bilayer-encapsulated gold nanosheets and nanocrystals by Zhijuan Wang; Junhua Yuan; Min Zhou; Li Niu; Ari Ivaska (pp. 6289-6293).

Single-crystal Au nanosheets and fcc gold nanocrystals of uniform size were synthesized by a novel and simple route. The results of field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) indicated the formation of the single-crystal structure of gold nanosheets and fcc nanocrystals. Energy-dispersive analysis of X-ray (EDAX) showed absorbance of cetyltrimethylammonium bromide (CTAB) molecules onto the surface of gold nanostructures. Moreover, zeta potential measurements showed that CTAB-coated nanostructures were positively charged and the zeta potential remained almost the same upon centrifugation and redispersion of the resulting nanostructures in methanol, confirming the high stability of the surfactant-protected nanocomposites. Evolution of the nanostructures during the reaction was monitored by TEM observations. The results indicated that the formation of the gold nanostructures followed a two-step mechanism with a bilayer CTAB structure on the surface of the gold nanostructures.

Keywords: Cetyltrimethylammonium bromide (CTAB); Gold nanosheets; Gold nanocrystals

Fluorine-doped zinc oxide transparent and conducting electrode by chemical spray synthesis by B.N. Pawar; Duk-Ho Ham; R.S. Mane; T. Ganesh; Byung-Won Cho; Sung-Hwan Han (pp. 6294-6297).

Highly transparent and conducting fluorine-doped zinc oxide thin films, consisting of spherical nanometer-sized grains, were synthesized onto soda-lime glass substrate by using a chemical spray unit. The effect of fluorine doping concentration in starting solution was investigated. Both doped and undoped films were preferentially oriented along [002] direction. Electrical resistivity decreases from 5.7 x 10^-2 to 8.6 x 10^-3 ohm-cm after 1 at.% fluorine doping, and increases for higher doping concentration. However, surface morphology of films obtained at 3 at.% fluorine doping appeared smooth and uniform. A shift of the edge of the optical transmission in the ultraviolet region as a result of fluorine doping was obtained.

Keywords: Chemical spray; Structural and optical properties; Metal oxides

Effects of different Ti-doping methods on the structure of pure-silica MCM-41 mesoporous materials by Aiju Zhang; Zhihong Li; Zicheng Li; Yi Shen; Yumei Zhu (pp. 6298-6304).

Pure-silica mesoporous materials doped by titanium have been prepared by direct synthesis method and post-synthetic impregnation method. The effects of different Ti-doping methods on the structure of pure-silica mesoporous materials have been researched. X-ray diffraction, transmission electron microscopy, scanning electronic microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray absorption spectrum and nitrogen adsorption–desorption isotherms have been employed to characterize the products. It has been found that structural properties were strongly related to the amount and the way of titanium introduction. The mesoporous ordering of the samples that have been prepared by direct synthesis method and post-synthetic method became poor with the increasing of titanium amount. The XANES and EXAFS spectra confirmed that the titanium have been inserted into the framework of MCM-41. The titanium grafted in the Ti-MCM-41 in fourfold coordination, and the titanium doped in the Ti/MCM-41 in higher coordination sites.

Keywords: PACS; 61.43.Gt; 61.72.WwMesoporous material; Ti-doping; Method; Structure

Effect of fluoride-ion implantation on the biocompatibility of titanium for dental applications by H.Y. Liu; X.J. Wang; L.P. Wang; F.Y. Lei; X.F. Wang; H.J. Ai (pp. 6305-6312).

This study stressed on the effect of fluoride-ion implantation upon the biocompatibility of titanium. By using plasma immersion ion implantation technique, fluoride ions were implanted into the smooth surface of pure titanium. The chemical composition and physical structure of the modified surface layers were characterized by X-ray photoelectron spectroscopy (XPS) as well as scanning electron microscope (SEM). At the same time, in vitro co-culture assays were performed to evaluate the biocompatibility of MG-63 cells to the modified titanium. It was confirmed by SEM observations that cell growth on the fluoride-ion-implanted titanium acquired better morphological characters. In addition, the cells on the fluoride-ion-implanted titanium showed the more increasingly and rapidly substrates-attaching capabilities than those on the non-implanted titanium via aridine orange stain assay. Fluoride-ion-implanted titanium could increase the percentages of cells in S phase but without affecting the ratios of cells in G₀/G₁ and G₂/M phases was confirmed by flow cytometry assay. The current results indicated that fluoride-ion implantation could improve the biocompatibility of titanium.

Keywords: PACS; 87.85.J−Titanium; Fluoride; Ion implantation; MG-63 cells; Biocompatibility

Room temperature deposition of crystalline indium tin oxide films by cesium-assisted magnetron sputtering by Deuk Yeon Lee; Hong-Koo Baik (pp. 6313-6317).

Indium tin oxide (ITO) films were deposited on a Si (100) substrate at room temperature by cesium-assisted magnetron sputtering. Including plasma characteristics, the structural, electrical, and optical properties of deposited films were investigated as a function of cesium partial vapor pressure controlled by cesium reservoir temperature. We calculated the cesium coverage on the target surface showing maximum formation efficiency of negative ions by means of the theoretical model. Cesium addition promotes the formation efficiency of negative ions, which plays important role in enhancing the crystallinity of ITO films. In particular, the plasma density was linearly increased with cesium concentrations. The resultant decrease in specific resistivity and increase in transmittance (82% in the visible region) at optimum cesium concentration (4.24×10⁻⁴Ωcm at 80°C of reservoir temperature) may be due to enhanced crystallinity of ITO films. Excess cesium incorporation into ITO films resulted in amorphization of its microstructure leading to degradation of ITO crystallinity. We discuss the cesium effects based on the growth mechanism of ITO films and the plasma density.

Keywords: Crystalline indium tin oxide; Room temperature; Cesium-assisted sputtering; Formation efficiency of negative ions; Plasma density; Specific resistivity

Effect of spraying power on the microstructure and mechanical properties of supersonic plasma-sprayed Ni-based alloy coatings by X.C. Zhang; B.S. Xu; S.T. Tu; F.Z. Xuan; H.D. Wang; Y.X. Wu (pp. 6318-6326).

The aim of this paper was to investigate the microstructure and mechanical properties of the supersonic plasma-sprayed Ni–Cr–B–Si–C coatings prepared at different spraying powers. The microstructure, phase composition, porosity, Young's modulus, micro-hardness, and residual stresses of the coatings were investigated and determined. The variations of the porosity, Young's modulus and micro-hardness of the coatings were evaluated by using statistical method. Results showed that the variations of porosity, Young's modulus and micro-hardness of the coatings followed the Weibull distributions. With increasing the porosity, the micro-hardness and Young's modulus of the coating decreased. The mean value of the Young's modulus of the coating calculated from Weibull plot was almost proportional to the square root of the micro-hardness of the coating. With increasing the power, Young's modulus of the coating increased, which, in turn, resulted in the increment of the residual stress at the coating surface.

Keywords: Plasma spraying; Spraying power; Porosity; Mechanical properties; Statistical analysis

Adsorption of carbon monoxide on Pd(311) and (211) surfaces by Jing Zhang; Xuena Zhang; Zexin Wang; Zhaoyu Diao (pp. 6327-6331).

Adsorption of carbon monoxide on Pd(311) and (211) stepped surfaces has been investigated by the extended London-Eyring-Polyani-Sato (LEPS) method constructed using a 5-parameter Morse potential. The calculated results show that there exist common characteristics of CO adsorption on the two surfaces. At low coverage, CO occupies threefold hollow site of the (111) terrace and is tilted with respect to the surface normal. Among the threefold hollow sites on the (111) terrace, the nearer the site is to the step, the greater is the influence of the step. The twofold bridge site on the (100) step is also a stable adsorption site at high coverage. Because of the different lengths of the (111) terraces, the (311) and (211) stepped surfaces have different characteristics. A number of new sites are exposed on the boundary regions, including the fourfold hollow site (H₄) of the (311) surface and the fivefold hollow site (H₅) of the (211) surface. At high coverage, CO resides in the H₅ site of the (211) surface, but the H₄ site of the (311) surface is not a stable adsorption site. This study further shows that the on-top site on the (100) step of Pd(311) is a stable adsorption site, but the same type of site on Pd(211) is not.

Keywords: The extended LEPS; CO/Pd(3; 1; 1) system; CO/Pd(2; 1; 1) system; Stable adsorption site

Solvent effect on the formation of self-assembled monolayer on DLC surface between n-hexane and Vertrel XF by Manlin Tan; Huayu Zhang; Yulei Wang; Hongtao Ma; Jiaqi Zhu; Jiecai Han (pp. 6332-6336).

Self-assembled monolayers of 1 H,1 H,2 H,2 H-perfluorodecyltrichloro-silane (FDTS) have been deposited on the diamond-like carbon (DLC) film-coated magnetic heads with two different solvents, n-hexane and Vertrel XF. In order to investigate the solvent effect on the monolayer formation, a series of FDTS monolayers were prepared by varying the solution concentrations which were respectively characterized by time-of-flight mass spectroscopy, contact angle measurements and atomic force microscopy. Results showed that high density of aggregations were present for the FDTS monolayers using the n-hexane solvent, while the monolayer formed on the DLC surface using the Vertrel XF solvent exhibited excellent quality and reproducibility and no aggregations were observed.

Keywords: PACS; 73.30. +ySelf-assembled monolayer; Solvent effect; Formation; Diamond-like carbon

Choline oxidase immobilized into conductive poly(3,4-ethylenedioxythiophene) film for choline detection by Hongjuan Zeng; Yadong Jiang; Junsheng Yu; Guangzhong Xie (pp. 6337-6340).

The effect of choline oxidase (Chox) on the electrochemical polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) was described. Result shows that the growth rate of PEDOT film varied with the addition of Chox quantity. The properties of PEDOT and PEDOT/Chox films were characterized by XPS and UV–vis absorption techniques. Meanwhile, a novel UV–vis absorbance method for the detection of choline was achieved. In a medium of 1/30M phosphate buffer solution (pH 8.0), a very sensitive absorbance peak at 293nm was observed. The linear relationship between UV–vis absorption intensity and choline concentration in a range from 1.0×10⁻⁶ to 5.1×10⁻⁵M was obtained. This method has also been applied to determine choline in several feedstuff additive samples.

Keywords: Electrochemical polymerization; PEDOT film; Choline oxidase (Chox); Choline detection

The optical properties of the blends of CdSe nanocrystals and poly( N-vinylcarbazole) by Feng Teng; Aiwei Tang; Bin Feng; Zhidong Lou (pp. 6341-6345).

The CdSe nanocrystals with different sizes were synthesized in aqueous solution through water–sol method usingl-cysteine hydrochloride as the stabilizer. The pH-dependent optical properties of the CdSe nanocrystals were investigated. Furthermore, the CdSe nanocrystals were dispersed into chloroform by using a cationic surfactant, and mixed with poly( N-vinylcarbazole) (PVK) in different mass ratios. The investigation of the photoluminescence (PL) and absorption spectra of the CdSe:PVK blends suggested that energy transfer from the PVK excited states to the CdSe nanocrystals, and it is more efficient for the smaller size nanocrystals. In the meantime, it was found that the relative emission intensity of the CdSe nanocrystals to PVK in the blends depended on the mass ratios, and the emission from the CdSe nanocrystals was the strongest as the mass ratio of CdSe to PVK was 2:1.

Keywords: PACS; 68.65.−k; 74.25.Gz; 77.84.Lf; 83.50.XaOptical properties; CdSe nanocrystals; Poly(; N; -vinylcarbazole); Energy transfer

Influence of oxygen post-treatment on laser-induced damage of antireflection coatings prepared by electron-beam evaporation and ion beam assisted deposition by Lei Yuan; Congjuan Wang; Yuanan Zhao; Jianda Shao (pp. 6346-6349).

Antireflection coatings at the center wavelength of 1053nm were prepared on BK7 glasses by electron-beam evaporation deposition (EBD) and ion beam assisted deposition (IBAD). Parts of the two kinds of samples were post-treated with oxygen plasma at the environment temperature after deposition. Absorption at 1064nm was characterized based on surface thermal lensing (STL) technique. The laser-induced damage threshold (LIDT) was measured by a 1064-nm Nd:YAG laser with a pulse width of 38ps. Leica-DMRXE Microscope was applied to gain damage morphologies of samples. The results revealed that oxygen post-treatment could lower the absorption and increase the damage thresholds for both kinds of as-grown samples. However, the improving effects are not the same.

Keywords: PACS; 42.79.Wc; 79.20.Rf; 61.80.BaAntireflection coating; Oxygen post-treatment; Laser-induced damage

Mechanical properties of Ti(C_0.7N_0.3) film produced by plasma electrolytic carbonitriding of Ti6Al4V alloy by Xin-Mei Li; Yong Han (pp. 6350-6357).

Porous nanocrystalline Ti(C_0.7N_0.3) film on Ti6Al4V substrate was prepared by plasma electrolytic carbonitriding (PECN). The film was characterized and analyzed by using a variety of analytical techniques, such as XRD, SEM, EDX, TEM, FESEM, Rockwell C indenter, scratch tester, Vickers microhardness tester and ring-on-block tribometer. The results showed that the film was about 15μm thick and its hardness was Hv 2369 at a load of 0.2N. The adhesion of the film was characterized by Lc and Pc value, and was found to be about 42N and more than 800N, respectively. The friction coefficients and wear volume loss of the PECN-treated samples sliding against a steel counterpart were much less than those of the untreated Ti6Al4V. The film possessed a good wear-resistance and antifriction under oil-lubricated condition due to its high hardness, adhesion and fracture toughness. Also, the porous surface morphology of the Ti(C_0.7N_0.3) film contributed to the enhanced tribological resistance by promoting the formation of lubricant film and entrapping wear debris.

Keywords: PACS; 61.82.Rx; 68.35.Gy; 81.65. LpPlasma electrolytic carbonitriding; Ti(C; _0.7; N; _0.3; ) thick film; Ti6Al4V; Adhesion; Wear-resistance

As-doped p-type ZnO films grown on SiO₂/Si by radio frequency magnetron sputtering by J.C. Fan; Z. Xie (pp. 6358-6361).

p-Type ZnO:As films with a hole concentration of 10¹⁶–10¹⁷cm⁻³ and a mobility of 1.32–6.08cm²/Vs have been deposited on SiO₂/Si substrates by magnetron sputtering. XRD, SEM, Hall measurements are used to investigate the structural and electrical properties of the films. A p–n homojunction comprising an undoped ZnO layer and a ZnO:As layer exhibits a typical rectifying behavior. Our study demonstrates a simple method to fabricate reproducible p-type ZnO film on the SiO₂/Si substrate for the development of ZnO-based optoelectronic devices on Si-based substrates.

Keywords: PACS; 73.61.Ga; 71.55.Gs; 78.55.EtArsenic dopant; p-Type ZnO film; SiO; ₂; /Si substrate; Homojunction

Sol–gel preparation and photoluminescence property of YBO₃:Eu³⁺/Tb³⁺ nanocrystalline thin films by Hongliang Zhu; Li Zhang; Tiantai Zuo; Xiaoyun Gu; Zhengkai Wang; Luming Zhu; Kuihong Yao (pp. 6362-6365).

YBO₃:Eu³⁺/Tb³⁺ nanocrystalline thin films were successfully deposited onto quartz glass substrates by Pechini sol–gel dip-coating method, using rare-earth nitrates and boric acid as starting materials. The crystal structure, morphology, chemical composition and photoluminescence property of the films were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and fluorescence spectrophotometer. The results of XRD, AFM, XPS and FTIR revealed that the films were composed of spherical YBO₃:Eu³⁺/Tb³⁺ nanocrystals with average grain size of 80nm. The YBO₃:Eu³⁺ film exhibited strong orange emission at 595nm and red emission at 615nm, which were, respectively ascribed to the (⁵D₀→⁷F₁) and (⁵D₀→⁷F₂) transitions of Eu³⁺. The YBO₃:Tb³⁺ film showed dominant green emission at 545nm due to the⁵D₄–⁷F₅ transition of Tb³⁺.

Keywords: PACS; 8.55.Hx; 78.66.Nk; 81.15.Lm; 81.20.FwPhosphors; Film; Sol–gel method; Borates; Photoluminescence

Further experimental evidences of thermal spreading of tungsten oxide on zirconia by Marco A. Fraga; Angela M. Lavogade Esteves; Lucia G. Appel (pp. 6366-6369).

The effects brought about by the time of thermal treatment as well as the water content in the gas phase during the thermal spreading of WO₃ on zirconia were investigated. Diffuse reflectance UV–vis spectroscopy evidenced the thermal spreading phenomenon and revealed the formation of polymeric tungsten dispersed species. Neither the thermal treatment time nor the water content showed to influence the nature of the dispersed species, which reveal to present thermodynamically preferential molecular structures. Infrared spectroscopy analysis of adsorbed pyridine evidenced that the polytungstate species lead to the generation of Brönsted acid sites. Lewis acid sites stronger than those naturally present on zirconia could also be detected in addition to weaker Lewis sites, which were associated to the WO₃ still present in the catalysts as showed by X-ray diffraction.

Keywords: Thermal spreading; Tungsten; Zirconia; Acidity

Mixed 2D molecular systems: Mechanic, thermodynamic and dielectric properties by Juraj Beňo; Martin Weis; Edmund Dobročka; Daniel Haško (pp. 6370-6375).

Study of Langmuir monolayers consisting of stearic acid (SA) and dipalmitoylphosphatidylcholine (DPPC) molecules was done by surface pressure–area isotherms ( π– A), the Maxwell displacement current (MDC) measurement, X-ray reflectivity (XRR) and atomic force microscopy (AFM) to investigate the selected mechanic, thermodynamic and dielectric properties based on orientational structure of monolayers. On the base of π– A isotherms analysis we explain the creation of stable structures and found optimal monolayer composition. The dielectric properties represented by MDC generated monolayers were analyzed in terms of excess dipole moment, proposing the effect of dipole–dipole interaction. XRR and AFM results illustrate deposited film structure and molecular ordering.

Keywords: PACS; 68.47.Pe; 81.07.−bLangmuir–Blodgett films; Maxwell displacement current; X-ray reflectivity; Atomic force microscopy; Monolayers; Electrical properties and measurements; Dielectric properties

The dynamics of hydrogen adsorption on polycrystalline uranium by S.G. Bazley; T.S. Nunney; C. Mormiche; B.E. Hayden (pp. 6376-6379).

The dynamics of dissociative hydrogen adsorption on clean polycrystalline uranium has been studied using temperature programmed desorption and supersonic molecular beams. The initial sticking probability was measured as a function of incident kinetic energy between 3 and 255meV. Two adsorption channels were observed; a non-activated direct channel was shown to be active over the entire energy range studied and a low energy indirect channel that was characterised by a decrease in sticking probability with increasing beam energy, and an insensitivity to both surface temperature and a range of hydrogen coverages. Together these results suggest the existence of an unaccommodated molecular precursor that has sufficient lifetime and mobility to locate favourable sites and dissociatively adsorb.

Keywords: Hydrogen; Uranium; Adsorption; Precursor

Electrochemical, morphological and microstructural characterization of carbon film resistor electrodes for application in electrochemical sensors by Carla Gouveia-Caridade; David M. Soares; Hans-Dieter Liess; Christopher M.A. Brett (pp. 6380-6389).

The electrochemical and microstructural properties of carbon film electrodes made from carbon film electrical resistors of 1.5, 15, 140Ω and 2.0kΩ nominal resistance have been investigated before and after electrochemical pre-treatment at +0.9V vs SCE, in order to assess the potential use of these carbon film electrodes as electrochemical sensors and as substrates for sensors and biosensors. The results obtained are compared with those at electrodes made from previously investigated 2Ω carbon film resistors. Cyclic voltammetry was performed in acetate buffer and phosphate buffer saline electrolytes and the kinetic parameters of the model redox system Fe(CN)₆^3−/4− obtained. The 1.5Ω resistor electrodes show the best properties for sensor development with wide potential windows, similar electrochemical behaviour to those of 2Ω and close-to-reversible kinetic parameters after electrochemical pre-treatment. The 15 and 140Ω resistor electrodes show wide potential windows although with slower kinetics, whereas the 2.0kΩ resistor electrodes show poor cyclic voltammetric profiles even after pre-treatment. Electrochemical impedance spectroscopy related these findings to the interfacial properties of the electrodes. Microstructural and morphological studies were carried out using contact mode Atomic Force Microscopy (AFM), Confocal Raman spectroscopy and X-ray diffraction. AFM showed more homogeneity of the films with lower nominal resistances, related to better electrochemical characteristics. X-ray diffraction and Confocal Raman spectroscopy indicate the existence of a graphitic structure in the carbon films.

Keywords: Carbon film electrodes; Carbon film resistors; Cyclic voltammetry; Electrochemical impedance spectroscopy; Contact mode AFM; Confocal Raman spectroscopy; X-ray diffraction

Composition of the sputter deposited W–Ti thin films by N. Bundaleski; S. Petrović; D. Peruško; J. Kovač; A. Zalar (pp. 6390-6394).

Tungsten–titanium (W–Ti) thin film was deposited by dc Ar⁺ sputtering of W(70at.%)–Ti(30at.%) target. The thin film composition, determined by X-ray photoelectron spectroscopy (XPS) depth profiling, is W_(0.77±0.07)Ti_(0.08±0.03)O_(0.15±0.03). The presence of oxygen in the deposit is due to the rather poor vacuum conditions during the deposition, while significant deficiency of Ti, as compared to the sputtering target composition cannot be explained straightforwardly. Monte Carlo simulations of both, transport of sputtered particles from target to the substrate through the background gas (SRIM 2003 program) and thin film sputtering during the XPS depth profiling (program TRIDYN_FZR) are presented. The simulations show that the particle transport through the background gas is mainly responsible for the Ti depletion: the estimated composition of the thin film is W_0.61Ti_0.16O_0.23. Additional apparent Ti depletion occurs due to the preferential sputtering during the thin film composition analysis. The simulation of the sputtering process show that the surface concentration measured by XPS should be about W_0.74Ti_0.11O_0.15. The discrepancy between the estimated surface composition and the actual experimental result is in the range of the experimental error.

Keywords: PACS; 81.15.Cd; 68.35.Dv; 79.60−i; 02.70.UuW–Ti thin films; Sputtering deposition; Preferential sputtering; XPS; Monte Carlo

Self-lubricative coating grown by micro-plasma oxidation on aluminum alloys in the solution of aluminate–graphite by Xiaohong Wu; Wei Qin; Yun Guo; Zhaoyang Xie (pp. 6395-6399).

Aluminum trioxide ceramic coatings with high hardness were grown on surfaces of 2024 Aluminum alloys by micro-plasma oxidation in an aluminate electrolytic solution, which highly improve wear-resisting properties of 2024 Aluminum alloys. However, ceramic coating surfaces are porous and very coarse, which is disadvantageous to practical applications. In this paper, in order to increase the density of the pores and decrease the friction coefficient of the ceramic coatings, different concentrations (2–8g/l) of graphite were added into the aluminate electrolytic solution. The thickness and hardness of the produced ceramic coatings were measured by HVS-100 micro-hardness tester and thickness tester. The friction coefficient of the coatings was studied by a frictionometer. The phase composition and surface morphology of the MPO films were evaluated through X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the thickness of the ceramic coating is about 22±1μm, surfaces of the ceramic coatings are very uniform and that the coatings consist of mainly aluminum trioxides and a certain amount of graphite, which indicates graphite have entered the ceramic films during the micro-plasma oxidation process. Wear properties results show that the friction coefficient of the ceramic coatings decreased when graphite entered the ceramic films. When the concentration of graphite is 4g/l, the wear properties of the coatings is the most excellent and the friction coefficient decreases to the lowest, that is 0.09.

Keywords: Micro-plasma oxidation; 2024 Aluminum alloys; Wear resistance; Graphite

X-ray photoelectron and Raman studies of microwave Plasma Assisted Chemical Vapour Deposition (PACVD) diamond films by Bernard Humbert; Nesrine Hellala; Jean Jacques Ehrhardt; Silvère Barrat; Elizabeth Bauer-grosse (pp. 6400-6409).

X-ray photoelectron and Raman spectroscopies were used to investigate the chemical and the structural properties of thin diamond films synthesised by Plasma Assisted Chemical Vapour Deposition (PACVD). Continuous polycrystalline diamond films were grown under different plasma conditions and based on the combination of detailed XPS and Raman spectroscopic analysis two main topics are highlighted (i) the stress measurements were discussed by distinguishing clearly the chemical effects from the mechanical effects; (ii) an electronic gap at 2.7eV probed by Raman resonance that corresponds to an energy loss peak on the XPS carbon signal, was related to the surface hydrogenation.

Keywords: Diamond films; XPS; Raman; Internal stresses; Chemical vapour deposition; Diamond; X-ray spectroscopy; Raman spectroscopy; Stress measurements; Coatings

Annealing effects on the optical and structural properties of Al₂O₃/SiO₂ films as UV antireflection coatings on 4H-SiC substrates by Feng Zhang; Weifeng Yang; Aisuo Pang; Zhengyun Wu; Hongji Qi; Jianke Yao; Zhengxiu Fan; Jianda Shao (pp. 6410-6415).

Al₂O₃/SiO₂ films have been prepared by electron-beam evaporation as ultraviolet (UV) antireflection coatings on 4H-SiC substrates and annealed at different temperatures. The films were characterized by reflection spectra, ellipsometer system, atomic force microscopy (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. As the annealing temperature increased, the minimum reflectance of the films moved to the shorter wavelength for the variation of refractive indices and the reduction of film thicknesses. The surface grains appeared to get larger in size and the root mean square (RMS) roughness of the annealed films increased with the annealing temperature but was less than that of the as-deposited. The Al₂O₃/SiO₂ films maintained amorphous in microstructure with the increase of the temperature. Meanwhile, the transition and diffusion in film component were found in XPS measurement. These results provided the important references for Al₂O₃/SiO₂ films annealed at reasonable temperatures and prepared as fine antireflection coatings on 4H-SiC-based UV optoelectronic devices.

Keywords: Annealing; Al; ₂; O; ₃; /SiO; ₂; films; 4H-SiC; External quantum efficiency

The effect of Pd addition to Fe as catalysts on growth of carbon nanotubes by TCVD method by S.Z. Mortazavi; A. Reyhani; A. Iraji zad (pp. 6416-6421).

The effects of Pd addition to Fe (Pd/Fe=0, 2.5/7.5, 5/5, 7.5/2.5 and 1) and growth temperatures (920 and 970°C) on density, diameter and growth mode of carbon nanotubes (CNTs) have been studied. SEM observations and TG analyses confirmed that the CNT yields depend on Pd/Fe ratios as (7.5/2.5)>(5/5)>Pd>(2.5/7.5)>Fe at both growth temperatures. TEM data showed that addition of Pd results in tip growth mode. From Raman spectroscopy data, the order of samples’ structural quality ( I_G/ I_D ratio) are Fe>Pd/Fe (2.5/7.5)>(5/5)>(7.5/2.5)>Pd and the I_G/ I_D ratios increase by decreasing the growth temperature. Films with higher concentration of Fe (Pd/Fe=0, 2.5/7.5) contain some single-walled carbon nanotubes.

Keywords: Carbon nanotube; Thermal chemical vapor deposition; Pd/Fe catalyst

Growth of thin Si oxide in a cyclic oxygen plasma environment below 200°C by Jaehyun Moon; Yong-Hae Kim; Choong-Heui Chung; Su-Jae Lee; Dong-Jin Park; Yoon-Ho Song (pp. 6422-6427).

The growth of Si oxide by means of a cyclic radio-frequency (rf) plasma oxidation process has been explored in a low temperature range of 100–200°C. The growth mechanism exhibits Cabrera–Mott (CM) oxidation, that is, the transport of mobile ionic species is assisted by an electric field. The low activation energy of 0.3eV is attributed to the small size of O⁻ and the assistance of the electric field. The oxide becomes off-stoichiometric as one approaches to the exterior surface of the oxide layer.

Keywords: PACS; 52.50.Qt; 68.47.Gh; 81.15.AaOxygen plasma; Si; Oxidation; Growth kinetics; Ion transport

Ferromagnetism of Mn_xLi_yZn1− x−_yO films by Zhou Xueyun; Ge Shihui; Yao Dongsheng; Zuo Yalu; Xiao Yuhua (pp. 6428-6431).

We had prepared Mn-doped ZnO and Li, Mn codoped-ZnO films with different concentrations using spin coating method. Crystal structure and magnetic measurements demonstrate that the impurity phases (ZnMnO₃) are not contributed to room temperature ferromagnetism and the ferromagnetism in Mn-doped ZnO film is intrinsic. Interesting, saturated magnetization decreases with Mn or Li concentration increase, showing that some antiferromagnetism exists in the samples with high Mn or Li concentration. In addition, Mn_0.05Zn_0.95O film annealed in vaccum shows larger ferromagnetism than the as-prepared sample and more oxygen vacancies induced by annealing in reducing atmosphere enhance ferromagnetism, which supports the bound magnetic polaron model on the origin of room temperature ferromagnetism.

Keywords: Li codoping; Annealing; Oxygen vacancies

Synthesis and photoluminescence of water-soluble Mn²⁺-doped ZnS quantum dots by Qi Xiao; Chong Xiao (pp. 6432-6435).

The water-soluble Mn²⁺-doped ZnS quantum dots (Mn:ZnS d-dots) were synthesized by using thioglycolic acid (TGA) as stabilizer in aqueous solutions in air, and characterized by X-ray powder diffraction (XRD), UV–vis absorption spectra and photoluminescence (PL) emission spectroscopy. The sizes of Mn:ZnS d-dots were determined to be about 2nm using XRD measurements and the UV–vis absorption spectra. It was found that the Mn²⁺⁴T₁→⁶A₁ emission intensity of Mn:ZnS d-dots significantly increased with the increase of Mn²⁺ concentration, and showed a maximum when Mn²⁺ doping content was 1.5%. If Mn²⁺ concentration continued to increase, namely more than 1.5%, the Mn²⁺⁴T₁→⁶A₁ emission intensity would decrease. In addition, the effects of TGA/(Zn+Mn) molar ratio on PL were investigated. It was found that the peak intensity ratio of Mn²⁺⁴T₁→⁶A₁ emission to defect-states emission showed a maximum when the TGA/(Zn+Mn) molar ratio was equal to 1.8.

Keywords: Mn; ²⁺; -doped ZnS; Quantum dots; Water-soluble; Photoluminescence

Fabrication and optical properties of SnS thin films by SILAR method by Biswajit Ghosh; Madhumita Das; Pushan Banerjee; Subrata Das (pp. 6436-6440).

Although the fabrication of tin disulfide thin films by SILAR method is quiet common, there is, however, no report is available on the growth of SnS thin film using above technique. In the present work, SnS films of 0.20μm thickness were grown on glass and ITO substrates by SILAR method using SnSO₄ and Na₂S solution. The as-grown films were smooth and strongly adherent to the substrate. XRD confirmed the deposition of SnS thin films. Scanning electron micrograph revealed almost equal distribution of the particle size well covered on the surface of the substrate. EDAX showed that as-grown SnS films were slightly rich in tin component while UV–vis transmission spectra exhibited high absorption in the visible region. The intense and sharp emission peaks at 680 and 825nm (near band edge emission) dominated the photoluminescence spectra.

Keywords: PACS; 67.70.+n; 78.55.−m; 51.70.+fSnS; SILAR; Thin film; Photoluminescence

Polymeric like carbon films prepared from liquid gas and the effect of nitrogen by T. Ghodselahi; M.A. Vesaghi (pp. 6441-6445).

Polymeric like carbon (PLC) films are grown by a capacitance coupled RF-PECVD on the grounded electrode at room temperature from liquid gas (40% propane and 60% butane) in two regimes with nitrogen and without nitrogen gas. Films are characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Fourier transform infrared (FTIR) absorption and Raman spectroscopy. The result of FTIR analyses indicates that more than 90% of hydrogen atoms are bonded to carbon with sp³ hybridization. The abundance of CH₃ is more than that of CH₂ and this one is more than that of CH for carbon with sp³ hybridization in these films. The C 1s line of the XPS spectra is deconvoluted to several peaks that are attributed to the CH₃, CH₂ and CH terminations. The result of this deconvolution is consistent with FTIR results. AFM images show that the mean nanoparticle size is reduced from about 100nm for films without nitrogen to less than 80nm for films with nitrogen. This is in agreement with our Raman results. By addition of nitrogen to the feed gas, no variation in the C–H stretching vibration mode is observed. The effect of N–H bonds is observable in both FTIR and XPS spectra and a very small trace of N–C bonds is present only in deconvolution of N 1s line of XPS spectra. These results indicate that by addition of nitrogen to feed gas, internal structure of a-C:H nanoparticles is not changed but particle size is decreased. We suggest that the internal stress reduction due to nitrogen addition in the feed gas for PLC films can be related to decreasing of the a-C:H particle size.

Keywords: RF-PECVD; a-C:H nanoparticle; AFM; XPS; FTIR; Raman

Improvement of electrical and optical properties of Ga and N co-doped p-type ZnO thin films with thermal treatment by Manoj Kumar; Byung-Teak Lee (pp. 6446-6449).

Ga and N co-doped p-type ZnO thin films were epitaxially grown on sapphire substrate using magnetron sputtering technique. The process of synthesized Ga and N co-doped ZnO films was performed in ambient gas of N₂O. Hall measurement shows a significant improvement of p-type characteristics with rapid thermal annealing (RTA) process in N₂ gas flow, where more N acceptors are activated. The film rapid thermal annealed at 900°C in N₂ ambient revealed the highest carrier concentration of 9.36×10¹⁹cm⁻³ and lowest resistivity of 1.39×10⁻¹Ωcm. In room and low temperature photoluminescence measurements of the as grown and RTA treated film, donor acceptor pair emission and exciton bound to acceptor recombination at 3.25 and 3.357eV, respectively, were observed.

Keywords: PACS; 71.55.Gs; 73.61.Ga; 81.15.FgGa–N co-doping; Thermal treatment: Sputtering; ZnO

Structure and oil repellency by Stuart A. Brewer; Colin R. Willis (pp. 6450-6454).

Combining structure and liquid repellent coatings to optimise non-wettability is a well-established field. However, the area in recent years has been dominated by data on water repellency. The work here provides data on how certain plant structures can be used to develop surfaces that provide repellency towards both polar and non-polar, low surface tension fluids. Combining fluoropolymer coatings with ‘hairy’ fibres is particularly beneficial for providing liquid-repellent textiles. None of these surfaces can however be regarded as super-repellent to low surface tension liquids (i.e. with little difference in advancing and receding contact angles).

Keywords: Lotus leaf; Super-repellency; Super-hydrophobicity; Oil repellency

Optical inhomogeneity of ZnS films deposited by thermal evaporation by Xiaochun Wu; Fachun Lai; Limei Lin; Jing Lv; Binping Zhuang; Qu Yan; Zhigao Huang (pp. 6455-6460).

Zinc sulfide (ZnS) films with optical thickness (reference wavelength is 620nm) ranging from 310 to 1240nm were deposited on quartz substrates at room temperature by a thermal evaporation system. The structure and morphology of the films were investigated by X-ray diffraction, atomic force microscopy, respectively. The optical properties of the films were determined by in situ transmittance measurements and wideband spectra photometric measurements, respectively. The experimental results show that the films exhibit cubic structure, and the intensity of the (220) diffraction peak enhances with the increase of optical thickness. Surface grain size and surface roughness increase monotonously with increasing film thickness. Refractive indices and extinction coefficients calculated by in situ transmittance measurements are well consistent with those calculated by wideband spectra photometric measurements. Both the refractive index and packing density of the film increase as the increase of film thickness, which confirms the film is positive inhomogeneous and has an expanding columnar structure. Extinction coefficients of the films increase with increasing film thickness, which results from the increase of surface roughness.

Keywords: ZnS; Thin films; Optical properties; Optical inhomogeneity

Effect of aluminum on the morphological and textural properties of CuO–ZnO/H-Ferrierite by Jhonny Huertas Flores; Guillermo Solórzano; M. Isabel Pais da Silva (pp. 6461-6466).

Hybrid catalysts containing CuO–ZnO or CuO–ZnO–Al₂O₃ as the metallic component and the zeolite H-ferrierite as support were prepared by both the coprecipitation–impregnation and coprecipitation–sedimentation methods. They were characterized by XRD, BET, and TEM. Aluminum was added to the metallic component, and the effects on the hybrid catalyst properties were studied. The metallic component blocked the zeolite micropore volume, and spaces were created between agglomerate particles of the first component, increasing mesopore volume. Aluminum introduction at a Cu/Zn/Al ratio of 55/30/15 favored the formation of hydrotalcite as a precursor to CuO/ZnO/Al₂O₃. In this case, small, highly dispersed particles of these oxides were obtained. In the coprecipitation–impregnation method, greater contact between the H-ferrierite zeolite and the metallic component was observed.

Keywords: CuO–ZnO–Al; ₂; O; ₃; H-ferrierite; Coprecipitation–impregnation; Coprecipitation–sedimentation

The influence of repellent coatings on surface free energy of glass plate and cotton fabric by Lidija Černe; Barbara Simončič; Matjaž Željko (pp. 6467-6477).

The aim of this research was to determine the influence of chemical finishes on the surface properties of glass plate, considered as a model homogeneous smooth surface and cotton fabric as a non-ideal heterogeneous rough surface. Microscopic slides and 100% cotton fabric in plain weave were coated with fluorocarbon polymers (FCP), paraffin waxes with zirconium salts (PWZ), methylolmelamine derivatives (MMD), polysiloxanes with side alkyldimethylammonium groups (PSAAC) and aminofunctional polysiloxanes (AFPS). From the goniometer contact angle measurements of different liquids, the surface free energy of the coated glass plates was calculated according to approaches by Owens–Wendt–Kaelble, Wu, van Oss–Chaudhury–Good, and Li–Neumann–Kwok. The results showed that all the coatings decreased the surface free energy of the substrate, which was also influenced by the liquid combination and the theoretical approach used. In spite of the fact that the liquid contact angles were much higher on the coated fabric samples than on glass plates and resulted in the lower values of work of adhesion, a very good correlation between the coatings deposited on both substrates was obtained. The presence of repellent coatings FCP, PWZ and MMD converted the solid surface from polar to highly apolar by masking the functional groups of glass and cellulose. PSAAC and AFPS coatings did not decrease the solid surface free energy to such an extent as the former three coatings due to their monopolar character.

Keywords: Glass coating; Textile finishing; Contact angle; Goniometry; Surface free energy; Work of adhesion; Influence of finish

Study of vacancy on diamond (100) (2×1) surface from first-principles by Run Long; Ying Dai; Lin Yu; Hao Jin; Baibiao Huang (pp. 6478-6482).

Structure and energy related properties of neutral and charged vacancies on relaxed diamond (100) (2×1) surface were investigated by means of density functional theory. Calculations indicate that the diffusion of a single vacancy from the top surface layer to the second layer is not energetically favored. Analysis of energies in charged system shows that neutral state is most stable on diamond (100) (2×1) surface. The multiplicity of possible states can exist on diamond (100) surface in dependence on the surface Fermi level, which supports that surface diffusion of a vacancy is mediated by the change of vacancy charge states. Analysis of density of states shows surface vacancy can be effectively measured by photoelectricity technology.

Keywords: Diamond (1; 0; 0) surface; Vacancy; Density functional theory

Synthesis of zinc oxide nanosheet thin films and their improved field emission and photoluminescence properties by annealing processing by Wei Bai; Xia Zhu; Ziqiang Zhu; Junhao Chu (pp. 6483-6488).

ZnO nanosheet thin films have been synthesized through a solvothermal route. These obtained nanosheets disperse quasi-vertically and homogenously on the copper substrates and range in thickness from 80nm to 250nm. The as-grown nanosheet thin films were then annealed in the oxygen-presented atmosphere. Field emission plots indicate that the value of turn-on field is reduced from 2.86V/μm to 1.52V/μm and the corresponding value of threshold field decreases from 7.19V/μm to 4.45V/μm after annealing processing. Room temperature photoluminescence spectrum from the sample annealed at 850°C in almost pure oxygen atmosphere shows only UV emission and a blue shift while the visible light band is unobservable compared with those of the other two samples, indicating that the crystalline quality of the obtained zinc oxide nanosheet thin films is greatly improved through annealing treatment. This solution approach combined with annealing treatment can, therefore, be regarded as a convenient route to fabricate high-quality crystalline ZnO nanomaterials.

Keywords: PACS; 75.55.Gs; 85.15.−z; 78.66.−w; 85.45.DbZnO; Nanosheets thin films; Annealing processing; Photoluminescence (PL); Field emission (FE)

Laser cladding of in situ TiB₂/Fe composite coating on steel by Baoshuai Du; Zengda Zou; Xinhong Wang; Shiyao Qu (pp. 6489-6494).

To enhance the wear resistance of mechanical components, laser cladding has been applied to deposit in situ TiB₂/Fe composite coating on steel using ferrotitanium and ferroboron as the coating precursor. The phase constituents and microstructure of the composite coating were investigated using X-ray diffraction (XRD), scanning electron micrograph (SEM) and electron probe microanalysis (EPMA). Microhardness tester and block-on-ring wear tester were employed to measure the microhardness and dry-sliding wear resistance of the composite coating. Results show that defect-free composite coating with metallurgical joint to the steel substrate can be obtained. Phases presented in the coating consist of TiB₂ and α-Fe. TiB₂ particles which are formed in situ via nucleation-growth mechanism are distributed uniformly in the α-Fe matrix with blocky morphology. The microhardness and wear properties of the composite coating improved significantly in comparison to the as-received steel substrate due to the presence of the hard reinforcement TiB₂.

Keywords: In situ; TiB; ₂; /Fe composite coating; Laser cladding; Ferrotitanium; Ferroboron

Interaction of amines with native aluminium oxide layers in non-aqueous environment: Application to the understanding of the formation of epoxy-amine/metal interphases by D. Mercier; J.-C. Rouchaud; M.-G. Barthés-Labrousse (pp. 6495-6503).

Interaction of propylamine (PA), 1,2-diaminoethane (DAE) or 3-aminomethyl-3,5,5-trimethylcyclohexylamine (isophorone diamine, IPDA) with native aluminium oxide layers in non-aqueous environment has been studied using time-resolved inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray photoelectron spectroscopy (XPS). The formation of several surface complexes has been evidenced. Monodentate and bidentate metal-bond surface complexes (MBSC) result from interactions between the amine terminations of the molecule and aluminium cations by donation of the N lone electron pair to the metal ion (Lewis-like mechanism leading to OAl⋯N bonds). Monodentate and bidentate hydrogen-bond surface complexes (HBSC) are due to interaction of the amino group with surface hydroxyl groups by protonation of the amine termination (Brønsted-like mechanism leading to the formation of AlOH⋯N bonds) or interaction with carbonaceous contamination (C_xO_yH_z⋯N bonds). Diamines can also form mixed complexes with one amino group forming an O–Al⋯N bond and the other group forming an AlOH…N or C_xO_yH_z⋯N bond. AlOH⋯N and C_xO_yH_z…N bonds are less stable under vacuum than OAl⋯N bonds, leading to partial desorption of the DAE molecules in vacuum and modification of the interaction modes. Only DAE and IPDA can lead to partial dissolution of the aluminium native (hydr)oxide films. A detailed mechanism of dissolution has been proposed based on the formation of mononuclear bidentate (chelate) MBSC by ligand exchange between the terminal η¹-OH and bridged μ₂-OH surface sites and the amino terminations of the molecule. The detachment of this complex from the surface is likely to be the precursor step to the formation of the interphase in epoxy-amine/metal systems.

Keywords: PACS; 82.65.+r; 82.45.Jn; 68.43−h; 82.35.Gh; 68.08.−p; 82.80.Pv; 82.30.RsDiamines; Aluminium; Ligand exchange; Dissolution; Epoxy-amine adhesive joints; Interphase

Simulation of composition modification in ZnSe by nanosecond radiation of excimer laser by S.P. Zhvavyi; G.L. Zykov (pp. 6504-6508).

A numerical simulation of the composition modification induced in ZnSe by nanosecond irradiation of the KrF excimer laser ( λ=248nm, τ=20ns) has been carried out. Intensive evaporation of components has shown to results in the material surface cooling and forming a nonmonotone temperature profile with maximum temperature in semiconductor volume at the distance of ∼6nm from the surface. As a result of evaporation and diffusion of components formation of the near-surface layer with nonstoichiometric composition takes place and enrichment of selenium reaches maximum value not on the surface, but in the semiconductor volume.

Keywords: PACS; 61.50.Nw; 61.80.B; 78.55.EtLaser irradiation; ZnSe; Melting; Solidification; Evaporation; Nonstoichiometric composition

Effect of intrinsic stress on the optical properties of nanostructured ZnO thin films grown by rf magnetron sputtering by Rajesh Kumar; Neeraj Khare; Vijay Kumar; G.L. Bhalla (pp. 6509-6513).

In this paper we report the effect of deposition temperature on the structural and optical properties of ZnO thin films prepared by rf magnetron sputtering. The films grown at lower deposition temperatures were in a state of large compressive stress, whereas the films grown at higher temperature (450°C) were almost stress free. In the absorption spectra, the ZnO excitonic and the Zn surface plasmon resonance (SPR) peaks have been observed. A redshift in the optical band gap of ZnO films has also been observed with the increase in the deposition temperature. The shift in the band gap calculated from the size effect did not match with the observed shift values and the observed shift has been attributed to the compressive stress present in the films.

Keywords: Stress; Optical properties; ZnO

First-principles calculations of ethanethiol adsorption and decomposition on GaN (0001) surface by Chun-Li Hu; Yong Chen; Jun-Qian Li; Yong-Fan Zhang (pp. 6514-6520).

The adsorption and decomposition of ethanethiol on GaN (0001) surface have been investigated with first-principles calculations. The DFT calculations reveal that ethanethiol adsorbs dissociatively on the clean GaN (0001) surface to form ethanethiolate and hydrogen species. An up limit coverage of 0.33 for ethanethiolate monolayer on GaN (0001) surface is obtained and the position of the sulfur atom and the tilt angle of the thiolate chain are found to be very sensitive to the surface coverage. Furthermore, the reactivity of ethanethiol adsorption and further thermal decomposition reactions on GaN (0001) surface is discussed by calculating the possible reaction pathways and ethene is found to be the major product.

Keywords: PACS; 68.43.Bc; 68.47.FgGaN (0; 0; 0; 1) surface; Ethanethiol; DFT; Adsorption; Packing structure; Thermal decomposition

Functional multi-walled carbon nanotube/polysiloxane composite films as supports of PtNi alloy nanoparticles for methanol electro-oxidation by Zhi-Cai Wang; Zheng-Ming Ma; Hu-Lin Li (pp. 6521-6526).

We demonstrate the use of molecular monolayers to enhance the nucleation of electrocatalytically active PtNi alloy nanoparticles onto the multi-walled carbon nanotubes (MWCNTs). After the siloxane was polymerized on the nanotube surfaces, the carbon nanotubes were embedded within the polysiloxane shell with a hydrophilic amino group situated outside. Subsequent deposition of PtNi nanoparticles led to high density of 3–10nm diameter PtNi alloy nanoparticles uniformly deposited along the length of the carbon nanotubes. The presence of MWCNTs and PtNi in the composite films was confirmed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersion X-ray spectra analysis (EDS). The electrocatalytic activity of the PtNi-modified MWCNT/polysiloxane (PtNi/Si-MWCNT) composite electrode for electro-oxidation of methanol was investigated by cyclic voltammetry (CV), and excellent electrocatalytic activity can be observed.

Keywords: Multi-walled carbon nanotubes; Polysiloxane; Composite film; PtNi alloy; Methanol electro-oxidation

Synergistic effect of silver seeds and organic modifiers on the morphology evolution mechanism of silver nanoparticles by Aili Wang; Hengbo Yin; Min Ren; Yuming Liu; Tingshun Jiang (pp. 6527-6536).

Triangular, truncated triangular, quadrangular, hexagonal, and net-structured silver nanoplates as well as decahedral silver nanoparticles were manipulatively prepared starting from silver nitrate and silver seeds in the presence of poly(ethylene glycol) (PEG), poly( N-vinyl pyrrolidone) (PVP), and Tween 80 at room temperature, respectively. UV–vis spectroscopy, XRD, HRTEM, SAED, and FTIR were used to illustrate the crystal growth process and to characterize the resultant silver nanoparticles. It was found that the silver seeds and organic modifiers synergistically affected the morphology evolution of the silver nanoparticles. The co-presence of silver seeds and PEG was beneficial to the formation of triangular and truncated triangular silver nanoplates; the silver seeds and PVP favored the formation of polygonal silver nanoplates; the silver seeds and Tween 80 preferred to the formation of net-structured silver plates. The morphology evolution of the resultant silver nanoparticles was correlated with the crystallinity of the silver seeds and the adsorption ability of the organic modifiers on the crystal surfaces.

Keywords: Silver; Nanoparticles; Morphology; Organic modifier; Silver seeds

Morphological and structural characterizations of different oxides formed on the stainless steel by Nd:YAG pulsed laser irradiation by Chengyun Cui; Jiandong Hu; Yuhua Liu; Kun Gao; Zuoxing Guo (pp. 6537-6542).

The effects of laser surface irradiation on microstructure of AISI 304 stainless steel were investigated. The stainless steel surface was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). XRD patterns indicated that different oxides, such as chromium oxides and manganese oxides were fabricated successfully on the surface of the stainless steel by Nd:YAG pulsed laser irradiation. The effects of the growth conditions such as the laser power density on the morphologies of the different oxides have been investigated. From the FESEM, EDS (energy-dispersive spectrum) and TEM observations, the oxides with triangle-like, quadrangular and hexagonal morphologies have been fabricated successfully. The XPS was used to verify the formed oxides which had been detected by the XRD patterns. It was considered that laser power density had a critical role in the formation of different oxides.

Keywords: Stainless steel; Nd:YAG pulsed laser; Oxides; XPS; TEM

Surface functionalization of carbon nanofibers by sol–gel coating of zinc oxide by Dongfeng Shao; Qufu Wei; Liwei Zhang; Yibing Cai; Shudong Jiang (pp. 6543-6546).

In this paper the functional carbon nanofibers were prepared by the carbonization of ZnO coated PAN nanofibers to expand the potential applications of carbon nanofibers. Polyacrylonitrile (PAN) nanofibers were obtained by electrospinning. The electrospun PAN nanofibers were then used as substrates for depositing the functional layer of zinc oxide (ZnO) on the PAN nanofiber surfaces by sol–gel technique. The effects of coating, pre-oxidation and carbonization on the surface morphology and structures of the nanofibers were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM), respectively. The results of SEM showed a significant increase of the size of ZnO nanograins on the surface of nanofibers after the treatments of coating, pre-oxidation and carbonization. The observations by SEM also revealed that ZnO nanoclusters were firmly and clearly distributed on the surface of the carbon nanofibers. FTIR examination also confirmed the deposition of ZnO on the surface of carbon nanofibers. The XRD analysis indicated that the crystal structure of ZnO nanograins on the surface of carbon nanofibers.

Keywords: PACS; 68.37.-d; 68.37.Hk_v; 81.05.-tElectrospinning; Carbon nanofiber; Surface; Coating; Zinc oxide

Conducting antimony-doped tin oxide films derived from stannous oxalate by aqueous sol–gel method by Tong Jun Liu; Zheng Guo Jin; Li Rui Feng; Tao Wang (pp. 6547-6553).

Nanocrystalline SnO₂:Sb films were prepared by a sol–gel route using C₆H₈O₇–triethanolamine (TEA) mixing aqueous solution with pH 6.5–7.0. Stannous oxalate and antimony trichloride were used as tin and antimony sources. IR, XRD FESEM, FETEM, UV–vis and four-point probe measurement were used to characterize sol–gel chemistry, structure, morphologies, optical and electrical properties. Mechanism of sol–gel reaction illuminated that existence of TEA supplied large numbers of active tin hydrate and ionized state carboxyl groups for tin and antimony chelation through the amido association with the ionized H⁺ on –COOH of H₃L and H₂C₂O₄. The 6at.% Sb-doped films with film thickness of 600nm had sheet resistance as low as 42.85Ω/ when annealed at 450°C for 10min. Annealing temperature intensively altered sheet resistance and optimum was in the range of 450–500°C. The longer annealing time caused Sb volatilization which led to the optimum doping level shifted from 6 to 12at.%.

Keywords: PACS; 71.20.Nr; 61.46.+wAntimony-doped tin oxide films; Tin oxalate; Sol–gel chemistry; Electrical properties

High temperature annealing effect on structure, optical property and laser-induced damage threshold of Ta₂O₅ films by Cheng Xu; Qiling Xiao; Jianyong Ma; Yunxia Jin; Jianda Shao; Zhengxiu Fan (pp. 6554-6559).

Ta₂O₅ films were deposited by conventional electron beam evaporation method and then annealed in air at different temperature from 873 to 1273K. It was found that the film structure changed from amorphous phase to hexagonal phase when annealed at 1073K, then transformed to orthorhombic phase after annealed at 1273K. The transmittance was improved after annealed at 873K, and it decreased as the annealing temperature increased further. The total integrated scattering (TIS) tests and AFM results showed that both scattering and root mean square (RMS) roughness of films increased with the annealing temperature increasing. X-ray photoelectron spectroscopy (XPS) analysis showed that the film obtained better stoichiometry and the O/Ta ratio increased to 2.50 after annealing. It was found that the laser-induced damage threshold (LIDT) increased to the maximum when annealed at 873K, while it decreased when the annealing temperature increased further. Detailed damaged models dominated by different parameters during annealing were discussed.

Keywords: Ta; ₂; O; ₅; films; Annealing; Laser-induced damage threshold; Scattering; Absorption

Different dispersion behavior of glucose and sucrose on alumina and silica surfaces by Y. Wang; L. Lin; B.S. Zhu; Y.X. Zhu; Y.C. Xie (pp. 6560-6567).

Phenomena of spontaneous monolayer-dispersion have been found in many salt and oxide/support systems as well as in organic compound/support systems. In this paper, the dispersion behaviors of glucose and sucrose have been systematically compared using three types of alumina with different textures and one type of silica gel, as supports. The dispersion capacity of the saccharides was determined by XRD quantitative phase analysis and confirmed by DTA-TG and FT-IR results. The pore size distribution of carbon-covered alumina (CCA) derived from the saccharide/alumina composite was employed to evaluate the dispersion state of the saccharide precursor. It was found that both sucrose and glucose are dispersed on the alumina and silica surfaces as a monolayer when their loading is kept under the monolayer-dispersion capacity. However, at higher saccharide content, glucose and sucrose are dispersed differently. Just like other monolayer-dispersion systems, sucrose begins to form in the crystalline phase when its loading exceeds the monolayer-dispersion capacity. In contrast, glucose aggregates in an amorphous state in the pores of the supports until these pores are filled, and only then forms crystalline glucose.

Keywords: Monolayer-dispersion; Glucose; Sucrose; Alumina; Silica; Carbon-covered alumina

The effect of surface modification by nitrogen plasma on photocatalytic degradation of polyvinyl chloride films by L. Xiao-jing; Q. Guan-jun; C. Jie-rong (pp. 6568-6574).

The solid-phase photocatalytic degradation of poly(vinyl chloride) (PVC) films was investigated under the ambient air in order to assess the feasibility of developing photodegradable polymers. Nitrogen plasma was used to modify PVC films to enhance the photocatalytic degradation of PVC with nano-sized anatase TiO₂. The plasma parameter varied in this study is discharge power from 30 to 120W for a constant treatment time of 60s and a constant gas pressure of 10Pa. The photodegradation of the plasma-treated PVC–TiO₂ films was compared with that of pure PVC films and PVC–TiO₂ films performing weight loss monitoring, scanning electron microscopy (SEM) analysis, contact angle measurements, electron spin resonance (ESR), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The wettability of the plasma-treated PVC is improved significantly. ESR revealed that the signal of radicals on the surface of the plasma-treated PVC film was enhanced after the treatment. Furthermore, the weight loss indicated that TiO₂ speeds up the photocatalytic degradation of PVC chains. The SEM image of the plasma-treated PVC–TiO₂ film showed a lot of crack on the film surface after irradiation. XPS indicated that the C and Cl atomic concentration reached minimum values on the surface of plasma-treated PVC–TiO₂ under identical photocatalytic condition. The experimental results reveal that plasma treatment can obviously enhance the photocatalytic degradation of PVC.

Keywords: PACS; 52.40.HfPlasma; Nano-sized TiO; ₂; PVC; Photocatalysis; Solid-phase; Degradation

Study of adsorption of bovine serum albumin to Langmuir–Blodgett film coated surfaces using work of adhesion as a tool by S. Sandhya; Muthuselvi Lakshmanan; A. Dhathathreyan (pp. 6575-6579).

This work reports on the use of rate of change of work of adhesion (Δ W) as a tool to study adsorption of bovine serum albumin (BSA) to glass and Langmuir–Blodgett film of dihexadecyl phosphate (DHP) and dioctadecyl dimethyl ammonium bromide (DOMA) coated surfaces. Pure BSA and BSA with additives – sorbitol and urea – have been adsorbed to bare glass surfaces and DHP and DOMA coated surfaces. The results suggest that an increase in Δ W with time indicates promotion of adsorption while a decrease indicates hindered adsorption. Further adsorption of BSA was most effective on DHP coated surface compared with bare glass and DOMA coated glass. In case of mixtures of BSA with urea and sorbitol, BSA+urea showed hindered adsorption while adsorption of BSA+sorbitol was efficient for all substrates.

Keywords: Adsorption; Work of adhesion; BSA; LB film coated surface

Application of multivariate analysis of TOF-SIMS spectra for studying the effect of high glucose intake on aortic lipid profile by Ylva Magnusson; Peter Friberg; Per Malmberg; Yun Chen (pp. 6580-6585).

To study the effect of long-term glucose feeding on aortic lipid composition by using the time of flight-secondary ion mass spectrometry (TOF-SIMS).Rats were divided into two groups, drinking water with or without 10% glucose from birth to 6 months of age. The aortic wall was dissected out, high-pressure frozen, freeze-fractured, freeze-dried and analyzed by TOF-SIMS using a Bismuth cluster ion source. Surface spectra were taken from standardized regions of the vessel wall.Different peaks, such as cholesterol, fatty acids (FAs) and diacylglycerols (DAGs), were identified by the principal component analysis as carries of variance between two groups. These peaks were then compared by conventional t-test. Our data showed that the intensity of cholesterol, but not FAs and DAGs, was significantly decreased in the glucose-drinking rat. Moreover, the long-term glucose intake changed ratios between different FAs in the aorta.The long-term glucose intake led to decreased cholesterol intensity in the aortic wall and this effect was revealed through a global analytical approach with objective selection of significant variables.

Keywords: TOF-SIMS; Principal component analysis; High glucose intake; Aorta; Fatty acid; Diacylglycerol; Cholesterol

GaN-based light-emitting diode with ZnO nanotexture layer prepared using hydrogen gas by Lung-Chien Chen; Cheng-Ban Chung (pp. 6586-6589).

ZnO films were deposited on indium tin oxide (ITO), which formed the transparent conductive layer (TCL) of a GaN-based light-emitting diode (LED), by ultrasonic spraying pyrolysis to increase the light output power. The ZnO nanotexture was formed by treating the as-deposited ZnO films with hydrogen. The root mean square (RMS) roughness increased from 4.47 to 7.89nm before hydrogen treatment to 10.82–15.81nm after hydrogen treatment for 20min. Typical current–voltage ( I– V) characteristics of the GaN-based LEDs with a ZnO nanotexture layer have a forward-bias voltage of 3.25V at an injection current of 20mA. The light output power of a GaN-based LED with a ZnO nanotexture layer improved to as much as about 27.5% at a forward current of 20mA.

Keywords: ZnO nanotexture; Spraying pyrolysis method; Hydrogen treatment; GaN

Effect of the oxygen flow rate on the structure and the properties of Ag–Cu–O sputtered films deposited using a Ag/Cu target with eutectic composition by J.F. Pierson; E. Rolin; C. Clément-Gendarme; C. Petitjean; D. Horwat (pp. 6590-6594).

Ag–Cu–O films were deposited on glass substrates by reactive sputtering of a composite Ag₆₀Cu₄₀ target in various Ar–O₂ mixtures. The films were characterised by energy dispersive X-ray analysis, X-ray diffraction, UV–visible spectroscopy and using the four point probe method. The structure of the films is strongly dependent on the oxygen flow rate introduced in the deposition chamber. The variation of the oxygen flow rate allows the deposition of the following structures: Ag–Cu–(O) solid solution, nc-Ag+nc-Cu₂O, nc-Ag+nc-(Ag,Cu)₂O and finally X-ray amorphous. UV–visible reflectance measurements confirm the occurrence of metallic silver into the deposited films. The increase of the oxygen flow rate induces a continuous increase of the film oxygen concentration that can be correlated to the evolution of the film reflectance and the film electrical resistivity. Finally, the structural changes vs. the oxygen content are discussed in terms of reactivity of sputtered atoms with oxygen.

Keywords: Reactive sputtering; Nanostructured films; Structure; Silver–copper oxides; Electrical properties

Plasma nitriding of low alloy steels at floating and cathodic potentials by Liang Wang; Yang Li; Xuemin Wu (pp. 6595-6600).

The low alloy steels were nitrided in the plasma atmosphere generated by using hollow cathode discharge. For comparison, specimens of 40 Cr steel were in two different potential states. One kind is isolated from cathode and anode between them the discharge was created. The other kind is placed on the plate which is connected to the cathode. The nitriding was carried out at different temperatures. The surface morphology, phase of compound layers and microhardness profiles were analyzed. The optical microscopy observation and X-ray diffraction showed that the compound layers were formed in all experiments. The results of the nitriding treatment are weakly dependent on the potentials applied on the specimens.

Keywords: PACS; 81.65.Lp; 52.80.VpHollow cathode discharge; Plasma nitriding; Low alloy steel

Highly thermal stable transparent conducting SnO₂:Sb epitaxial films prepared on α-Al₂O₃ (0001) by MOCVD by Xianjin Feng; Jin Ma; Fan Yang; Feng Ji; Fujian Zong; Caina Luan; Honglei Ma (pp. 6601-6604).

Antimony-doped tin oxide (SnO₂:Sb) single crystalline films have been prepared on α-Al₂O₃ (0001) substrates by metal organic chemical vapor deposition (MOCVD). The antimony doping was varied from 2% to 7% (atomic ratio). Post-deposition annealing of the SnO₂:Sb films was carried out at 700–1100°C for 30min in atmosphere ambient. The effect of annealing on the structural, electrical and optical properties of the films was investigated in detail. All the SnO₂:Sb films had good thermal stability under 900°C, and the 5% Sb-doped SnO₂ film exhibited the best opto-electrical properties. Annealed above 900°C, the 7% Sb-doped SnO₂ film still kept high thermal stability and showed good electrical and optical properties even at 1100°C.

Keywords: PACS; 68.55.ag; 68.60.Dv; 81.15.GhAntimony-doped tin oxide films; MOCVD; Annealing

Effects of seed layer on the structure and property of zinc oxide thin films electrochemically deposited on ITO-coated glass by Sufeng Wei; Jianshe Lian; Xuejiao Chen; Qing Jiang (pp. 6605-6610).

ZnO films with different morphologies were deposited on the ITO-coated glass substrate from zinc nitrate aqueous solution at 65°C by a seed-layer assisted electrochemical deposition route. The seed layers were pre-deposited galvanostatically at different current densities ( i_sl) ranging from −1.30 to −3.0mA/cm², and the subsequent ZnO films had been done using the potentiostatic technique at the cathode potential of −1.0V. Densities of nucleation centers in the seed layers varied with increasing the current density, and the ZnO films on them showed variable morphologies and optical properties. The uniform and compact nanocrystalline ZnO film with (002) preferential orientation was obtained on seed layer that was deposited under the current density ( i_sl) of −1.68mA/cm², which exhibited good optical performances.

Keywords: PACS; 66.55.−a; 78.66.HF; 81.15.PqZnO; Seed layer; Electrodeposition; Nucleation; Nanocrystalline; Photoluminescence

Ion sputtering rates of W-, Ti- and Cr-carbides studied at different Ar⁺ ion incidence angles by A. Zalar; J. Kovač; B. Praček; P. Panjan; M. Čeh (pp. 6611-6618).

To study the ion sputtering rates of W-, Ti- and Cr-carbides, trilayer structures comprising C-graphite (59nm)/WC (50nm)/W (38nm), C-graphite (56nm)/TiC (40nm)/Ti (34nm) and C-graphite (46nm)/C₃C₂ (60nm)/Cr (69nm) with a tolerance ±2% were sputter deposited onto smooth silicon substrates. Their precise structural and compositional characterization by transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) revealed that the WC and Cr₃C₂ layers were amorphous, while the TiC layer had a polycrystalline structure. The ion sputtering rates of all three carbides, amorphous carbon and polycrystalline Cr, Ti and W layers were determined by means of Auger electron spectroscopy depth profiling as a function of the angle of incidence of two symmetrically inclined 1keV Ar⁺ ion beams in the range between 22° and 82°. The sputtering rates were calculated from the known thicknesses of the layers and the sputtering times necessary to remove the individual layers. It was found that the sputtering rates of carbides, C-graphite and metals were strongly angle dependent. For the carbides in the range between 36° and 62° the highest ion sputtering rate was found for Cr₃C₂ and the lowest for TiC, while the values of the sputtering rates for WC were intermediate. The normalized sputtering yields calculated from the experimentally obtained data for all three carbides followed the trend of theoretical results obtained by calculation of the transport of ions in solids by the SRIM code. The sputtering yields are also presented in terms of atoms/ion. Our experimental data for two ion incidence angles of 22° and 49° and reported values of other authors for C-graphite and metals are mainly inside the estimated error of about ±20%. The influence of the ion-induced surface topography on the measured sputtering yields was estimated from the atomic force microscope (AFM) measurements at the intermediate points of the corresponding layers on the crater walls formed during depth profiling.

Keywords: PACS; 81.65 Cf; 68.55.NqIon sputtering rates; Sputtering yields; Carbides; W; Ti; Cr; C; Depth profiling

Synthesis and characterization of brookite/anatase complex thin film by Chiaki Ohara; Teruhisa Hongo; Atsushi Yamazaki; Toshio Nagoya (pp. 6619-6622).

TiO₂ films were prepared on a silicon or soda-glass substrate using a sol suspension. The TiO₂ film on the silicon substrate was composed of pure anatase phase and showed almost no contaminations. In contrast, the TiO₂ film on the soda-glass substrate was composed of anatase and brookite phases. The diffusion of Na into the TiO₂ film on the soda-glass substrate was observed by XPS, and Na was concentrated on the surface of the film. The yield of the brookite phase increased with decreasing distance from the surface of the film on the soda-glass substrate. Na promoted the formation of the brookite phase, although the preparative procedure was used for anatase synthesis.

Keywords: Brookite; Anatase; TiO; ₂; Thin film

Pulsed electrodeposition of monocrystalline Ni nanowire array and its magnetic properties by Jinxia Xu; Keyu Wang (pp. 6623-6627).

By means of a porous template without removing the aluminium substrate, a technique of pulsed electrodeposition with an intermittent symmetric square pulse has successfully been applied to fabricate Ni nanowire array. The as-obtained nanowires have a diameter of about 60nm and exhibit high aspect ratio of more than 50. The electron diffraction pattern investigation demonstrates that the nanowires are single crystal. Moreover, a highly preferential orientation [220] of the as-obtained Ni nanowires with high purity decided by XRD has been obtained, and the preferred orientation is weakened remarkably by an annealing process. Furthermore, the investigation of magnetic properties by VSM indicates that the as-obtained Ni nanowire array has an obvious magnetic anisotropy and exhibits a good thermal stability.

Keywords: Alumina template; Nanowire array; Pulsed electrodeposition; Symmetric square pulse; Annealing

Investigating the effects of the interface defects on the gate leakage current in MOSFETs by Ling-Feng Mao (pp. 6628-6632).

The effects of the interface defects on the gate leakage current have been numerically modeled. The results demonstrate that the shallow and deep traps have different effects on the dependence relation of the stress-induced leakage current on the oxide electric field in the regime of direct tunneling, whereas both traps keep the same dependence relation in the regime of Fowler–Nordheim tunneling. The results also shows that the stress-induced leakage current will be the largest at a moderate oxide voltage for the electron interface traps but it increases with the decreasing oxide voltage for the hole interface traps. The results illustrate that the stress-induced leakage current strongly depends on the location of the electron interface traps but it weakly depends on the location of the hole interface traps. The increase in the gate leakage current caused by the electron interface traps can predict the increase, then decrease in the stress-induced leakage current, with decreasing oxide thickness, which is observed experimentally. And the electron interface trap level will have a large effect on the peak height and position.

Keywords: PACS; 73.40.Gk; 73.40.Qv; 74.50.+rDefects; MOSFETs; Tunneling; Stress-induced leakage current

Growth of multi-walled CNTs emitters on an oxygen-free copper substrate by chemical-vapor deposition by Xiaowei Yin; Qilong Wang; Chaogang Lou; Xiaobing Zhang; Wei Lei (pp. 6633-6636).

Field emission properties of carbon nanotubes directly grown on a well-polished oxygen-free copper substrate by chemical-vapor deposition (CVD) were studied. Ni was sputtered on the copper substrate as catalyst, and the reactant gas was acetylene. From scanning electron microscopic and transmission electron microscopic images, the as-grown carbon nanotubes are seen to be bamboo structure with branches. Efficient field emission of CNTs is measured by a diode configuration, and the maximum current is 4.8mA corresponding to a low electric field of 6.7V/μm (the emission area is about 3.14mm²). The diffusion between nickel and copper substrate is found to cause the loss of catalyst based on X-ray diffraction pattern of the surface of the substrate.

Keywords: Carbon nanotubes; CVD; Field emission

Quasi-horizontal GaN nanowire array network grown by sublimation sandwich technique by J.K. Jian; Cong Wang; M. Lei; Z.H. Zhang; T.M. Wang; X.L. Chen (pp. 6637-6641).

Quasi-horizontal GaN nanowire array network has been grown on Au-film-coated MgO substrates via a sublimation sandwich technique. These GaN nanowire arrays principally grew along two directions which were perpendicular to each other and nearly parallel to the substrate, forming a regular network. The formation of the nanowire network was a hetero-epitaxial vapor–liquid–solid (VLS) process assisted by Au catalysts and was dependent on the substrates. Transmission electron microscopy revealed that the nanowires were single-crystalline wurtzite GaN. Raman scattering spectrum of the nanowire network presented some new features.

Keywords: PACS; 81.07.Bc; 81.07.Vb; 81.16.HcNanostructures; Chemical vapor deposition processes; Semiconducting III–V materials

Microstructure and corrosion resistance behavior of ceramic coatings on biomedical NiTi alloy prepared by micro-arc oxidation by J.L. Xu; F. Liu; F.P. Wang; D.Z. Yu; L.C. Zhao (pp. 6642-6647).

In this paper, ceramic coatings were prepared on biomedical NiTi alloys by micro-arc oxidation (MAO) in constant voltage mode. The current density–time response was recorded during the MAO process. The microstructure, element distribution and phase composition of the coatings prepared at different MAO treatment times were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), thin-film X-ray diffraction (TF-XRD) and X-ray photoelectron spectroscopy (XPS). The corrosion behavior of the coatings in 0.9% NaCl solution was evaluated by the potentiodynamic polarization test. It is found that the coatings become more compact with increasing the MAO treatment time, and the growth rate of coating decreases. The results of TF-XRD, EDS and XPS indicate that the coatings are composed of a large amount of γ-Al₂O₃ and a little α-Al₂O₃, TiO₂ and Ni₂O₃. The Ni content of the coatings is about 3at.%, which is greatly lower than that of NiTi substrate. The bonding strength of coating-substrate is higher than 40MPa for all the samples in this study. The corrosion resistance of the coatings is about two orders of magnitude higher than that of the uncoated NiTi alloy.

Keywords: Micro-arc oxidation; NiTi alloy; Al; ₂; O; ₃; Ni content; Corrosion resistance

Comparison of annealing effects on Zn-doped GaMnAs and undoped GaMnAs epilayers by H. Nakagawa; J.T. Asubar; Y. Jinbo; N. Uchitomi (pp. 6648-6652).

To compare the annealing effects on GaMnAs-doped with Zn (GaMnAs:Zn) and undoped GaMnAs (u-GaMnAs) epilayers, we grew GaMnAs thin films at 200°C by molecular beam epitaxy (MBE) on GaAs substrates, and they were annealed at temperatures ranging from 220°C to 380°C for 100min in air. These epilayers were characterized by high-resolution X-ray diffraction (XRD), electrical, and magnetic measurements. A maximum resistivity at temperatures T_m close to the Curie temperatures T_c was observed from the measurement of the temperature-dependent resistivity ρ( T) for both the GaMnAs:Zn and the u-GaMnAs samples. We found, however, that the maximum temperature T_m observed for GaMnAs:Zn epilayers increased with increasing annealing temperature, which was different from the result with the u-GaMnAs epilayers. The formation of GaAs:Zn and MnAs or Mn–Zn–As complexes with increasing annealing temperature is most likely responsible for the differences in appearance.

Keywords: PACS; 71.55.Eq; 75.50.Pp; 81.05.Ea; 81.15.HiGaMnAs; Semiconducting materials; Spintronic devices; Molecular beam epitaxy; Post-growth annealing

Effect of superficially applied ZrO₂ inhibitor on the high temperature corrosion performance of some Fe-, Co- and Ni-base superalloys by G. Goyal; H. Singh; S. Prakash (pp. 6653-6661).

High temperature corrosion is an acute form of corrosion occurring at elevated temperature in the presence of an oxidizing gas and is associated with a thin electrolytic deposit (salt or ash) on alloy. Inhibitors and fuel additives have been used with varying success to combat oil ash corrosion. In this paper, the effect of an oxide additive namely ZrO₂ on the hot corrosion behaviour of some superalloys, viz. Superfer 800H (alloy A), Superco 605 (alloy B) and Superni 75 (alloy C) has been investigated in an Na₂SO₄–60%V₂O₅ environment at 900°C for 50 cycles. Each cycle consisted of 1h heating in a Silicon Carbide Tube furnace followed by 20min cooling in ambient air. Weight change measurements after each cycle were taken by an electronic balance having an accuracy of 0.01mg. XRD, SEM and EPMA analyses of the exposed specimens were carried out to characterize the oxide scales. In the Na₂SO₄–60%V₂O₅ environment, the corrosion rate for the Co-base alloy was found to be highest, whereas that for the Ni-base Superni 75 a lowest. Whereas, with ZrO₂ superficial coating, the overall weight gains got reduced for the alloys B and C, however the inhibitor was marginally effective in the alloy A. A thick scale was observed in the latter case, which was rich in Cr, Ni, Fe and V. Absence of protective continuous chromia layer and presence of less protective NiO was probably the main reason for more corrosion rate in this case.

Keywords: Hot corrosion; Superalloys; Inhibitors; Oxide additives; Oxide scales

Photoinduced energy transfer in blend films of hole and electron transport materials by Shuping Zhang; Weisi Song; Yinghui Wang; Yajing Peng; Yuqiang Liu; Yanqiang Yang (pp. 6662-6665).

The photoluminescence properties of the blend films consisting of the hole transport and electron transport materials, PVK and Alq₃, are studied by steady-state and time-resolved photoluminescence (PL) spectroscopy. Both the relative intensity and the photoluminescence lifetime are intensively dependent of the weight ratios of PVK and Alq₃. The detailed analysis of experiment data provides clear evidence for a Förster energy transfer from excited PVK, as donor, to Alq₃, as acceptor, based on nonradiative resonant transfer mechanism, and allows the determination of Förster radius and the concentration dependent energy transfer efficiency.

Keywords: Energy transfer; Photoluminescence; PVK; Alq; ₃

Effect of surface morphology of lead dioxide particles on their ozone generating performance by Jingping Wang; Xiang Li; Linghua Guo; Xiangjun Luo (pp. 6666-6670).

Lead dioxide is widely applied in anodic oxidation processes like the ozone generation and the degradation of various organic species in aqueous solution. In this paper, the correlation between the morphology of the lead dioxide particles and their ozone generating performance was investigated. The anode prepared by crude lead dioxide particles exhibited better performance in ozone generation than that prepared by milled lead dioxide particles. The reason lies in, probably, the higher stability of O on the surfaces of the crude lead dioxide particles. With 220-h running of the anode prepared with crude lead dioxide particles, the overall diameters of the lead dioxide particle decreased drastically, and many nano-scaled lead dioxide particles presented on the surfaces of the particles, which had resulted from recrystallization of the particles at high potentials. The two facts might be the main reason for the decline of the membrane electrode performance. Furthermore, a small percentage of α-lead dioxide detected in lead dioxide crystal may also decline the performance of the membrane electrode.

Keywords: Ozone; Crude lead dioxide; Milled lead dioxide; Recrystallization

Microstructure and properties of manganese dioxide films prepared by electrodeposition by G. Moses Jacob; I. Zhitomirsky (pp. 6671-6676).

Nanostructured manganese dioxide films were obtained by galvanostatic, pulse and reverse pulse electrodeposition from 0.01 to 0.1M KMnO₄ solutions. The deposition yield was investigated by in situ monitoring the deposit mass using a quartz crystal microbalance (QCM). Obtained films were studied by electron microscopy, X-ray diffraction analysis, energy dispersive spectroscopy, thermogravimetric and differential thermal analysis. The QCM and electron microscopy data were utilized for the investigation of deposition kinetics and film formation mechanism. It was shown that the deposition rate and film microstructure could be changed by variation of deposition conditions. The method allowed the fabrication of dense or porous films. The thickness of dense films was limited to ∼0.1μm due to the insulating properties of manganese dioxide and film cracking, attributed to drying shrinkage. Porous and crack-free 1–2μm films were obtained using galvanostatic or reverse pulse deposition from 0.02M KMnO₄ solutions. It was shown that film porosity is beneficial for the charge transfer during deposition and crack prevention in thick films. Moreover, porous nanostructured films showed good capacitive behavior for applications in electrochemical supercapacitors. The porous nanostructured films prepared in the reverse pulse regime showed higher specific capacitance (SC) compared to the SC of the galvanostatic films. The highest SC of 279F/g in a voltage window of 1V was obtained in 0.1M Na₂SO₄ solutions at a scan rate of 2mV/s.

Keywords: PACS; 68.47.Gh; 81.15.Pq; 82.47.Uv; 61.66.FnManganese dioxide; Porous films; Electron microscopy; Electrosynthesis; Capacitance

Effect of sputtered films on morphology of vertical aligned ZnO nanowires by J.P. Kar; S.W. Lee; W. Lee; J.M. Myoung (pp. 6677-6682).

Vertical aligned ZnO nanowires were grown by MOCVD technique on silicon substrate using ZnO and AlN thin films as seed layers. The shape of nanostructures was greatly influenced by the under laying surface. Vertical nanopencils were observed on ZnO/Si, whereas the nanowires on both sapphire and AlN/Si substrate have the similar aspect ratio. XRD patterns suggest that the nanostructures have good crystallinity. High-resolution transmission electron microscopy (HRTEM) confirmed the single crystalline growth of the ZnO nanowires along [001] direction. Room-temperature photoluminescence (PL) spectra of ZnO nanowires on AlN/Si clearly show a band-edge luminescence accompanied with a visible emission. More interestingly, no visible emission for the nanopencils on ZnO/Si substrates, were observed.

Keywords: PACS; 81.05.Dz; 81.07.−b; 81.15.GhZnO; Nanowires; Thin films; Morphology

Surface effect on the GSF energy of Al by Xiu-Mei Wei; Jian-Min Zhang; Ke-Wei Xu; Vincent Ji (pp. 6683-6686).

The second-nearest-neighbor modified embedded atom method (2NN-MEAM) is used to calculate the generalized stacking fault (GSF) energy for (111) surface of Al crystal. It is found that the GSF energy curve is much lower for the fault in the first layer of the (111) surface than that in the bulk. When the fault exists in the second layer, the energy curve becomes considerably on the verge of that in the bulk. With a much lower unstable stacking fault energy γ_usf, the dislocation should be easier to set on at the outermost of the free surface. Expansion in relaxation always exists for the stacking fault either in bulk or near the surface and the GSF energy increases with the vertical expansion.

Keywords: Surface effect; Stacking fault; Vertical expansion

Microstructure and properties of TiC–Fe36Ni cermet coatings by reactive plasma spraying using sucrose as carbonaceous precursor by Jinglei Zhu; Jihua Huang; Haitao Wang; Shouquan Zhang; Hua Zhang; Xingke Zhao (pp. 6687-6692).

This study is aimed to introduce an innovative precursor pyrolysis process to prepare Ti–Fe–Ni–C compound powder and to discuss and evaluate the relationship between microstructure and properties of TiC–Fe36Ni cermet coatings in-situ synthesized by reactive plasma spraying (RPS) of these compound powders. The main characteristic of the pyrolysis process is that sucrose (C12H22O11) is used as a source of carbon as well as a binder to bind reactive constituent particles. The compound powder with high bonding strength can avoid the problem that reactive constituent particles are separated during spraying. The TiC–Fe36Ni cermet coatings present typical splat-like morphology of thermally sprayed coatings and consist of two different areas: one is a composite reinforcement area where spherical fine TiC particles (100–500nm) homogeneously distribute within the Fe36Ni matrix; the other is an area of TiC accumulation. The surface hardness of the coatings reaches about 90±2 (HR15N). The maximum and average microhardness values of the coatings are 1930HV_0.2 (Vicker Hardness) and 1640HV_0.2, respectively. The average bonding strength of the coatings is about 62.3MPa. The wear resistance property of the coatings is much more than that of Ni60 alloys coatings.

Keywords: Sucrose; Reactive plasma spraying; TiC–Fe36Ni cermet coatings; In-situ synthesize; Microstructure

Preparation of visible-light responsive PF-codoped TiO₂ nanotubes by Xiuqin Chen; Xingwang Zhang; Yaling Su; Lecheng Lei (pp. 6693-6696).

Fabrication of PF-codoped TiO₂ nanotubes was carried out using a one-step electrochemical anodization process by tailoring the composition of the electrolyte with the aim of PF-codoping to extend the optical absorption of TiO₂ to the visible-light region. The as-prepared PF-codoped TiO₂ nanotubes were characterized by SEM, XPS, and UV–vis diffuse reflectance absorption spectra (DRS). The results showed that the tube diameter of the nanotubes was approximately 100nm and the tube length was approximately 510nm. The phosphorus and fluorine were successfully doped into TiO₂ nanotubes, as evidenced by XPS. Moreover, the PF-codoped samples displayed remarkably strong visible-light response.

Keywords: PACS; 81.16.Hc; 61.72.VvPhosphorus; Fluorine; Titanium dioxide; Nanotubes; Codoping

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Applied Surface Science (v.254, #20)

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Applied Surface Science (v.254, #20)