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Applied Surface Science (v.254, #15)

Quantum size effect of electron density in ultra-thin metal films and its influence on the interlayer relaxation by Fei Ma; Kewei Xu (pp. 4415-4420).

Further minimization of electronic devices and microelectromechanical systems (MEMS) requires the feature sizes of relevant materials to be shrunk significantly. In such a case, boundary effects, such as interfaces and surfaces, become remarkable, especially in nanometer scale, which must affect their microstructures and properties. In this work, we have analyzed the distribution of electron charge density in Cu and Al ultra-thin films using free electron model. The results show that an electrostatic field may come into being due to quantum size effect, and the interlayer separations must relax to decrease the Coulomb energy, the thinner the films, the larger the relaxation. More interestingly, two opposite deviating directions of the center of negative charges result in two absolutely distinct interlayer relaxations: inwards for Cu and outwards for Al.

Keywords: PACS; 68.35.−p; 73.20−rQuantum size effect; Electron density; Interlayer relaxation

A periodic density functional theory study of the dehydrogenation of methanol over CuCl(111) surface by Xia Wang; Wen-Kai Chen; Chun-Hai Lu (pp. 4421-4431).

The decomposition of methanol on clean and oxygen-precovered CuCl(111) surface have been studied with the method of density functional theory-generalized gradient approximation (DFT-GGA) and the periodic slab models. The effects of different methanol coverages up to one monolayer are investigated. The activation of the O–H bond of methanol to form the methoxide intermediate, the activation of the C–H bond to form the hydroxymethyl intermediate and the activation of the C–O bond to form methyl are examined. These intermediates can subsequently react to form methoxide, hydroxymethyl, methyl, formaldehyde, formyl, and finally CO on the surface. The chemisorption energies of CH₃OH, CH₃O, H₂COH, CH₃, H₂CO, HCO, OH and CO at their most favorable adsorption sites are predicted to be −57.9, −235.3, −172.9, −170.5, −67.8, −192.4, −309.5 and −105.7kJ/mol, respectively. We also confirm that the O–H bond-breaking paths have lower energy barrier, compared to the C–O and C–H bond-breaking paths. However, these reactions need a lower energy barrier when precovered oxygen atoms participate in these reactions.

Keywords: CuCl(1; 1; 1) surface; Methanol; Adsorption; Density functional theory

Synthesis and property of poly(trimethylolpropane triacrylate)/Al nanocomposite particle by in situ solution polymerization by Hui Liu; Hongqi Ye (pp. 4432-4438).

In order to improve its dispersibility and preserve its activity, nano-aluminum was encapsulated with poly(trimethylolpropane triacrylate) (PTMPTA) by in situ solution polymerization. The affecting factors of the conversion of monomer (CM), percentage of grafting (PG) and grafting efficiency (GE) were systematically studied. It was found that nano-aluminum had been evenly encapsulated with a layer of PTMPTA through chemical bond. And PTMPTA/Al nanocomposite particle with core-shell structure had been successfully synthesized. Compared to that of nano-aluminum, the dispersibility, corrosion resistance, thermal stability, especially the activity preservation (when it was used as additive in solid rocket propellants) of composite particle had been markedly improved.

Keywords: Poly(trimethylolpropane triacrylate); Composite particle; In situ solution polymerization; Activity preservation

Effects of substrates on the structure and dielectric properties of Ba(Sn_0.15Ti_0.85)O₃ thin films by Sannian Song; Lina Gao; Jiwei Zhai; Xi Yao; Zhiqun Cheng (pp. 4439-4443).

Ba(Sn_0.15Ti_0.85)O₃ (BTS) thin films were grown on Pt(111)/Ti/SiO₂/Si and LaNiO₃(LNO)/Pt(111)/Ti/SiO₂/Si substrates by a sol–gel processing technique, respectively. The BTS thin films deposited on annealed Pt(111)/Ti/SiO₂/Si and annealed LNO/Pt(111)/Ti/SiO₂/Si substrates exhibited strong (111) and perfect (100) orientations, respectively. The BTS thin films grown on un-annealed Pt(111)/Ti/SiO₂/Si substrates showed random orientation with intense (110) peak, while the films deposited on un-annealed LNO/Pt(111)/Ti/SiO₂/Si substrate exhibited random orientation with intense (100) peak, respectively. The dielectric constant of the BTS films deposited on annealed Pt(111)/Ti/SiO₂/Si, annealed LNO/Pt(111)/Ti/SiO₂/Si, un-annealed Pt(111)/Ti/SiO₂/Si and un-annealed LNO/Pt(111)/Ti/SiO₂/Si substrates was 512, 565, 386 and 437, respectively, measured at a frequency of 100kHz. A high tunability of 49.7% was obtained for the films deposited on annealed LNO/Pt(111)/Ti/SiO₂/Si substrate, measured at the frequency of 100kHz with an applied electric field of 200kV/cm. The high tunability has been attributed to the (100) texture of the films and larger grain sizes.

Keywords: PACS; 77.80.−e; 77.84.Dy; 81.20.Fw; 85.50.−nThin films; Sol–gel; Orientation; Dielectric properties; Tunability

Preparation of periodic mesoporous silica-included divacant Keggin units for the catalytic oxidation of styrene to synthesize styrene oxide by Xiaodan Yu; Leilei Xu; Xia Yang; Yingna Guo; Kexin Li; Jianglei Hu; Wei Li; Fengyan Ma; Yihang Guo (pp. 4444-4451).

Periodic mesoporous composite catalysts, [( n-C₄H₉)₄N]₄[γ-SiW₁₀O₃₄(H₂O)₂]/SBA-15 (TBA-1*/SBA-15, where TBA-1*=[( n-C₄H₉)₄N]₄[γ-SiW₁₀O₃₄(H₂O)₂]), with TBA-1* loadings of 4.3–14.8% were prepared by simultaneous hydrolysis and co-condensation of the tetraethoxysilane (TEOS) in the presence of divacant Keggin-type polyoxometalate and triblock copolymer surfactant (P123) followed by hydrothermal treatment process. Structure integrity of the Keggin unit in as-prepared composites was studied by Fourier transform infrared spectroscopy (FT-IR), Raman scattering spectra, and²⁹Si magic-angle spinning (MAS) NMR. Periodic mesoporous structure of the composites was evaluated by low-angle X-ray powder diffraction (LXRD) patterns, nitrogen porosimetry, and transmission electron microscope (TEM) measurements. As-prepared TBA-1*/SBA-15 was used as an heterogeneous oxidation catalyst for the styrene epoxidation reaction to synthesize styrene oxide in the presence of dilute H₂O₂ (30%), and influences of solvent, molar ratio of styrene to H₂O_2, TBA-1* loading on the styrene conversion, styrene oxide yield and selectivity were considered.

Keywords: PACS; 82.45.Jn; 95.30.FtMesoporous material; Styrene oxide; Epoxidation; Polyoxometalate; Sol–gel

Photocatalytic hydrogen generation over Eosin Y-Sensitized TS-1 zeolite by Xiaojie Zhang; Zhiliang Jin; Yuexiang Li; Shuben Li; Gongxuan Lu (pp. 4452-4456).

Eosin Y-sensitized TS-1 zeolite was studied for the photo-reduction of water into hydrogen driven by visible light ( λ≥420nm). The optimal pH and weight ratio between Eosin Y and TS-1 zeolite is 7 and 1/8, respectively. In the presence of triethanolamine (TEA) as an electron donor, the highest rate of hydrogen generation and apparent quantum efficiency are 34μmolh⁻¹ and 9.4%, respectively, under visible light irradiation ( λ≥420nm). Short-term stability test indicates that the catalyst is rather stable during 50h photoreaction.

Keywords: Photocatalytic; Eosin Y; TS-1 zeolite; H; ₂; generation; Visible light irradiations

Molecular imprinting and adsorption of metallothionein on nanocrystalline titania membranes by Zhen-Feng Cai; Hong-Juan Dai; Shi-Hui Si; Feng-Lian Ren (pp. 4457-4461).

Metallothionein (MT) imprinted TiO₂ membrane was synthesized via surface sol–gel process, using MT as template and TiO₂ sol as imprinted matrix. Appropriate template cavities in the TiO₂ sol–gel membrane were formed after the template molecules were removed on treatment with 1% NaOH solution. In situ technique of quartz crystal microbalance (QCM) was employed to study the molecular imprinting behavior of MT on nanocrystalline titania membranes. The imprinted membrane showed selectivity recognition for MT as compared to the other proteins. The amount of adsorption increased with the increasing of MT concentration both on imprinted membrane and non-imprinted membrane. The adsorption amount increased with the increasing of pH on imprinted membrane.

Keywords: PACS; 82.45.Mp; 87.14.Ee; 68.43.ehMetallothionein (MT); Molecular imprinting; Quartz crystal microbalance; Nanocrystalline titania

Visible-light photocatalytic behavior of two different N-doped TiO₂ by Jiwei Zhang; Yan Wang; Zhensheng Jin; Zhishen Wu; Zhijun Zhang (pp. 4462-4466).

The visible-light photocatalytic behavior of two different N-doped TiO₂ correlated with their physicochemical properties was investigated. The results show that N-TiO₂-1, prepared by a novel TiO₂ with unique defect structure, is more active in visible-light photocatalytic oxidation of C₃H₆ than N-TiO₂-2, prepared by standard P25-TiO₂ (Degussa). The specific rate constant of the former is ca. 5 times that of the latter. One model of photoactive center (V_o–NO–Ti) in anatase phase responsible for the visible-light photocatalytic activity is proposed. The higher the V_o–NO–Ti concentration is, the better the visible-light photocatalytic activity is.

Keywords: Nanotube titanic acid; N-doped titanium dioxide; Visible-light photocatalysis; Photoactive center

Chemical vapour etching for double-sided buried metallic contacts in polycrystalline silicon solar cells processing by M. Ben Rabha; M.F. Boujmil; M. Saadoun; H. Ezzaouia; B. Bessaïs (pp. 4467-4470).

In this paper, we investigate the effect of double-sided buried metallicontacts (BMCs) on the photovoltaic performances of polycrystalline-silicon (pc-Si) solar cells. Prior to junction formation, groove patterns were achieved on both surface sides of the pc-Si wafers using a chemical vapour etching-based technique. The BMCs were realized onto the grooved areas using the screen printing technique. Once the BMCs were formed, we point out a significant increase of the spectral response in the 400–1100nm wavelength range, particularly at short and long wavelengths. These results were attributed to an enlargement of the contact areas in both emitter and base regions of the cells, leading to a reduction of their effective thickness and to an enhancement of the minority carrier collection. The dark I– V characteristics of BMCs-based pc-Si cells show a significant reduction of the reverse current together with an improvement of the rectifying behaviour. The I– V characteristic under AM1.5 illumination shows that the introduction of BMCs in polycrystalline silicon solar cells processing improves the conversion efficiency by about 2.5–3.5%.

Keywords: Polycrystalline-Silicon; Solar cells; Etching; Grooving; Buried contacts

Interphase formation of a resin transfer molded silica–phenolics composites subjected to dynamic impregnation process by Baichen Wang; Yudong Huang (pp. 4471-4478).

In this study interphase formation of a resin transfer molded (RTMed) silica–phenolics composites subjected to dynamic impregnation process was investigated. The solvent effect on the interphase formation of silica fiber–phenolics composites was evaluated. UV–vis spectra, XPS and electron paramagnetic resonance (EPR) techniques were used to characterize the competitive adsorption of the components of phenolics solution onto silica reinforcement surfaces. Interlaminar shear strength (ILSS) and void content of silica–phenolics composites were also measured. It has been found that phenolics forms distribution gradient over RTM mold with respect to isomeric composition under the effect of solvent, which result, to varying extent, in the inhomogeneity of void content and thus ILSS of a final product. For the first time, it has been shown that the RTM process of silica–phenolics composites is highly solvent-dependent. Our work gives an insight into the role of organic solvent in a RTM solution impregnation processing and provides useful information and trends relating microscopic to macroscopic behavior.

Keywords: Silica fiber; Resin transfer molding (RTM); Phenolics; Solvent; Interphase

The reflectivity of Mo/Ag/Au ohmic contacts on p-type GaN for flip-chip light-emitting diode (FCLED) applications by Ming-Jer Jeng; Ching-Chuan Shiue; Liann-Be Chang (pp. 4479-4482).

The Mo/Ag/Au contact for flip-chip light-emitting diode (FCLED) applications is examined on its contact resistance and light reflectance. A high reflectance of 90% is achieved in un-annealed contact, but a strong inter-diffusion of ohmic metals and GaN during the annealing process is found to result in poor reflectance (55% at the wavelength of 465nm). The secondary ion mass spectrometry (SIMS) depth profiles indicate that a wide inter-diffusion region existed in the annealed contacts; thus the low reflectivity of the Mo/Ag/Au-annealed contacts can be attributed to the strong inter-diffusion of Au and Ag.

Keywords: PACS; 66.30.JtReflectivity; Ohmic contact; GaN; FCLED; Light reflectance; SIMS; Inter-diffusion

Synergistic inhibition effect of 2-mercaptobenzothiazole and Tween-80 on the corrosion of brass in NaCl solution by Karpagavalli Ramji; Darran R. Cairns; S. Rajeswari (pp. 4483-4493).

The corrosion inhibition of brass in 0.2M NaCl in the presence of 2-mercaptobenzothiazole (MBT) and polyoxyethylene sorbitan monooleate (Tween-80) has been investigated using potentiodynamic polarization, X-ray photoelectron spectroscopy and inductively coupled plasma analysis. Analysis of the results revealed that the addition of MBT and Tween-80 inhibits the corrosion of brass in 0.2M NaCl. Potentiodynamic polarization measurements showed that MBT acts as a mixed-type inhibitor and Tween-80 as an anodic inhibitor. Corrosion inhibition occurs through adsorption of the inhibitor on brass surface without modifying the corrosion mechanism. The adsorption of MBT and Tween-80 both follow Langmuir adsorption isotherm. Potentiodynamic polarization results suggested that the mixture of MBT and Tween-80 acts as a mixed-type inhibitor. Inhibition efficiency of 79.0 and 62.5% were obtained in the presence of optimum concentration of MBT and Tween-80, respectively. The addition of the mixture of MBT and Tween-80 enhanced the inhibition efficiency to 94.0% and showed a synergism of inhibition. XPS analysis indicated that MBT adsorbed on brass surface along with Tween-80 in the presence of the mixture of MBT and Tween-80. The results of solution analysis using ICP showed that the mixture of MBT and Tween-80 effectively controlled the dezincification of brass.

Keywords: Brass; 2-Mercaptobenzothiazole; XPS; Dezincification; Tween-80; NaCl; ICP

Influence of surface roughness and contact load on friction coefficient and scratch behavior of thermoplastic olefins by Han Jiang; Robert Browning; Jason Fincher; Anthony Gasbarro; Scooter Jones; Hung-Jue Sue (pp. 4494-4499).

To study the effects of surface roughness and contact load on the friction behavior and scratch resistance of polymers, a set of model thermoplastic olefins (TPO) systems with various surface roughness ( R_a) levels were prepared and evaluated. It is found that a higher R_a corresponds to a lower surface friction coefficient ( μ_s). At each level of R_a, μ_s gets larger as contact load increases, with a greater increase in μ_s as R_a level increases. It is also observed that with increasing contact load and increasing R_a, the μ_s tend to level off. In evaluating TPO scratch resistance, a lower μ_s would delay the onset of ductile drawing-induced fish-scale surface deformation feature, thereby raising the load required to cause scratch visibility. However, as the contact load is further increased, the μ_s evolves to become scratch coefficient of friction (SCOF) as significant sub-surface deformation and tip penetration occur and material displacement begins, i.e., ploughing. No dependence of R_a and μ_s on the critical load for the onset of ploughing is observed. In this work, the distinction between μ_s and SCOF will be illustrated. Approaches for improving scratch resistance of polymers via control of R_a are also discussed.

Keywords: PACS; 46.55.+d; 81.40.Pq; 68.35.CtSurface roughness; Friction coefficient; Scratch coefficient of friction; Scratch resistance; Thermoplastic olefins

Surface nature of nanoparticle zinc-titanium oxide aerogel catalysts by Chien-Tsung Wang; Jen-Chieh Lin (pp. 4500-4507).

Nanoparticle zinc-titanium oxide materials were prepared by the aerogel approach. Their structure, surface state and reactivity were investigated. Zinc titanate powders formed at higher zinc loadings possessed a higher surface area and smaller particle size. X-ray photoelectron spectroscopy (XPS) revealed a stronger electronic interaction between Zn and Ti atoms in the mixed oxide structure and showed the formation of oxygen vacancy due to zinc doping into titania or zinc titanate matrices. The 8–45nm aerogel particles were evaluated as catalysts for methanol oxidation in an ambient flow reactor. Carbon dioxide was favorably produced on the oxides with anion defects. Titanium based oxides exhibited a high selectivity to dimethyl ether, so that a strong Lewis acidic character suggested for the catalysts was associated primarily with the Ti⁴⁺ center. Both methanol conversion and dimethyl ether formation rates increased with increasing the zinc content added to the oxide support. Results demonstrate that cubic zinc titanate phases produce new Lewis acid sites having also a higher reactivity and that the nature of the catalytic surface transforms from Lewis acidic to basic characters due to the presence of reactive oxygen vacancies.

Keywords: Nanoparticles; Aerogels; Zinc titanate; Catalysts; Methanol oxidation

Preparation and characteristics of transparent p-type ZnO film by Al and N co-doping method by Li-Dan Tang; Yue Zhang; Xiao-Qin Yan; You-Song Gu; Zi Qin; Ya Yang (pp. 4508-4511).

Al–N co-doped ZnO films were fabricated by gaseous ammonia annealing at various temperatures. The structure and the electrical properties of Al–N-doped ZnO films strongly depend on the annealing temperature. XRD and SEM analysis indicate that the ZnO films possess a good crystallinity with c-axis orientation, uniform thickness and dense surface. Optical transmission spectra show a high transmittance (∼85%) in the visible region. Hall measurement demonstrates that ZnO films have p-type conduction with high carrier concentration of 8.3×10¹⁸cm⁻³ and low resistivity of 25.0Ωcm when the annealing temperature is 700°C. Also the growth process of Al–N co-doped at various temperatures is discussed in detail.

Keywords: PACS; 7280E; 6170A; 6855ZnO film; Magnetron sputtering; p-Type; Transparent film

Covalent immobilization of Pseudomonas cepacia lipase on semiconducting materials by Renny Edwin Fernandez; Enakshi Bhattacharya; Anju Chadha (pp. 4512-4519).

Lipase from Pseudomonas cepacia was covalently immobilized on crystalline silicon, porous silicon and silicon nitride surfaces. The various stages of immobilization were characterized using FTIR (Fourier transform infrared) spectroscopy. The surface topography of the enzyme immobilized surfaces was investigated using scanning electron microscopy (SEM). The quantity of the immobilized active enzyme was estimated by the para-nitrophenyl palmitate (pNPP) assay. The immobilized lipase was used for triglyceride hydrolysis and the acid produced was detected by a pH sensitive silicon nitride surface as a shift in the C– V (capacitance–voltage) characteristics of an electrolyte–insulator–semiconductor capacitor (EISCAP) thus validating the immobilization method for use as a biosensor.

Keywords: Lipase; Immobilization; Silanization; Glutaraldehyde; EISCAP; Triglyceride biosensor

Electrospinning method for the preparation of silver chloride nanoparticles in PVP nanofiber by Jie Bai; Yaoxian Li; Meiye Li; Shugang Wang; Chaoqun Zhang; Qingbiao Yang (pp. 4520-4523).

It has been successfully developed by the electrospinning technology that AgCl nanoparticles were incorporated into polymer fiber. In this paper, we chose poly(vinyl pyrrolidone) (PVP) because it was not only a good material for electrospinning but also it was excellent capping reagent of various metal nanoparticles. The silver ions interacted with the carbonyl groups in the PVP molecules. The formation of AgCl nanoparticles inside the PVP were carried out via the reaction of silver ions and HCl. TEM proved that most of the AgCl nanoparticles were uniformly dispersed in the PVP fibers.

Keywords: Poly(vinyl pyrrolidone) (PVP); AgCl nanoparticles; Electrospinning; Nanocomposites

A study of growth mechanism of KDP and ADP crystals by means of quantum chemistry by Yusuke Asakuma; Qin Li; H. Ming Ang; Moses Tade; Kouji Maeda; Keisuke Fukui (pp. 4524-4530).

Impurity adsorption, crystal growth by adsorption of growth unit and step-pinning mechanism of metal ion adsorption were investigated for potassium dihydrogen phosphate (KDP; KH₂PO₄) and ammonium dihydrogen phosphate (ADP; NH₄H₂PO₄) by quantum chemistry. In this study, the ideal crystal morphologies, the growth unit and the crystal surface with and without metal ions were calculated and analyzed by using electrostatic property. It is found that the computational results based on electrostatic potential distribution can account for the observed behaviours on KDP and ADP crystal growth.

Keywords: PACS; 81.10.DnAdsorption; Impurity effect; Step-pinning; Quantum chemistry

Growth of fullerene on Ag and hydrogen-passivated Si substrates: Effect of electron beam exposure on growth modes by M.V. Rundhe; B.N. Dev (pp. 4531-4538).

We have used Auger electron spectroscopy (AES) to investigate the effect of electron beam exposure on growth modes of fullerene (C₆₀) on substrates like Ag and hydrogen-passivated Si(111). The electron beam comprises of 3.4keV electrons, which are used in the AES study. To investigate the effect, Auger signal (AS) vs. deposition time ( t) measurements were conducted in a sequential mode, i.e., alternating deposition ofC60 and analysis using the electron beam. Duration of AES data collection after each deposition was the duration of exposure to electron beam in this experiment. For the growth study of C₆₀ on Ag, three AS– t plots were recorded for three different durations of exposure to electron beam. Changes in the AS– t plot, depending on the duration of exposure to the electron beam, reflect the electron beam-induced damage. Electron beam-induced damages of C₆₀ produce carbon materials of different densities and consequently transmission coefficient (α) of Auger electron through this material changes. In order to fit the AES (AS vs. t) data a model has been used which simultaneously provides the growth mode and the transmission coefficient. Observation of an increasing transmission coefficient with the increasing duration of exposure to the electron beam fromα=0.34 to 0.60 indicates the change of the nature of the carbon material due to the partial damage of C₆₀.

Keywords: PACS; 78.40.Ri; 82.80Pv; 61.80Fe; 81.15Aa.Fullerene; Growth of fullerene on Ag; Electron beam irradiation; Growth modes

Annealing effect on the structural and optical properties of a Cd1−_xZn_xS thin film for photovoltaic applications by S.D. Chavhan; S. Senthilarasu; Soo-Hyoung Lee (pp. 4539-4545).

Herein is a report of a study on a Cd1−_xZn_xS thin film grown on an ITO substrate using a chemical bath deposition technique. The as-deposited films were annealed in air at 400°C for 30min. The composition, surface morphology and structural properties of the as-deposited and annealed Cd1−_xZn_xS thin films were studied using EDX, SEM and X-ray diffraction techniques. The annealed films have been observed to possess a crystalline nature with a hexagonal structure. The optical absorption spectra were recorded within the range of 350–800nm. The band gap of the as-deposited thin films varied from 2.46 to 2.62eV, whereas in the annealed film these varied from 2.42 to 2.59eV. The decreased band gap of the films after annealing was due to the improved crystalline nature of the material.

Keywords: Chemical bath deposition (CBD); Cd; 1−; _x; Zn; _x; S; Thin films; Photovoltaic

Use of neural network method to characterize pressure controlled charge density of silicon nitride films deposited by PECVD by Byungwhan Kim; Su Yeon Kim (pp. 4546-4551).

A prediction model of charge density of silicon nitride (SiN) films was constructed by using a generalized regression neural network (GRNN). The SiN film was deposited by a plasma enhanced chemical vapor deposition (PECVD) system and the deposition process was characterized by means of a statistical experiment. The prediction performance of GRNN was optimized by using a genetic algorithm (GA) and yielded an improved prediction of about 63% over statistical regression model. The optimized model was utilized to qualitatively investigate the effect of process parameters under various pressures. A refractive index model was effectively utilized to validate charge density variations. For the variations in process parameters, charge density was strongly dependent on [N–H]. Effects of NH₃ or SiH₄ flow rates were significant only under high collision rate. Effect of pressure-induced collision rate was noticeable only at higher NH₃ flow rate or lower SiH₄ flow rate.

Keywords: Silicon nitride film; Charge density; Plasma enhanced chemical vapor deposition; Neural network; Model

Microstructure and selected properties of hot-work tool steel with PVD coatings after laser surface treatment by Marcin Adamiak; Leszek A. Dobrzański (pp. 4552-4556).

The paper presents the effect of HPD laser treatment on the microstructure and selected properties of the PVD CrN, (Ti,Al) and Ti(C,N) coatings deposited onto hot-work tool steel substrates. The microstructure and surface topography of the investigated samples are characteristic of the diversified morphology connected with the applied laser beam power. Employment of laser beam at 0.7kW power to the laser treatment of samples with Ti(C,N) coatings causes clear coating adhesion growth because of the diffusive processes induced by heat release. Because of the higher value of the (Ti,Al)N absorption coefficient one can state that the observed substrate materials change and finally coatings destruction in case of those samples is the most noticeable. The moderate effect of the laser beam treatment of the hot-work tool steel with the PVD coating was observed for CrN coatings. However, for laser beam power above 0.5kW differences in the thermal expansion coefficients of the substrate materials and coatings generate coating crackings.

Keywords: Microstructure; PVD coatings; Laser treatment; Mechanical properties; CrN; TiCN; TiAlN

Surface chemistry and catalytic activity of Ni/Al₂O₃ irradiated with high-energy electron beam by Jin Jun; Marshal Dhayal; Joong-Hyeok Shin; Young Hwan Han; Nikola Getoff (pp. 4557-4564).

The radiation effects induced effects by electron beam (EB) treatment on the catalytic activity of Ni/γ-Al₂O₃ were studied for the carbon dioxide reforming of methane with different EB energy and absorbed radiation dose. Transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to determine the change in structure and surface states of Ni/γ-Al₂O₃ catalyst before and after the EB treatment. Higher energy EB treatment is useful for increasing the proportion of the active sites (such as Ni⁰ and NiAl₂O₄-phase) on the surface. The increase of Ni/Al–ratio indicates that the Ni dispersion on the surface increased with the EB-treatment, resulting in an increase of the active sites, which leads to improving the catalytic activity. XPS measurement also showed a decrease of the surface carbon with EB dose. The maximum 20% increase in the conversion of CO₂/CH₄-mixture into CO/H₂ gas was observed for the catalyst treated with 2MeV energy and 600kGy dose of EB relative to untreated.

Keywords: CO; ₂; reforming of methane; Ni/γ-Al; ₂; O; ₃; Catalyst; Electron beam radiation

Investigation of ethene adsorption on Hmordenite and modified Hmordenite by frequency response method by Feifei Li; Xinghuai Gui; Daosheng Liu; Lijuan Song; Zhaolin Sun (pp. 4565-4571).

The frequency response (FR) technique has been applied to study adsorption mechanism of ethene in parent Hmordenite (HMor) and the HMor (CuO/HMor, Cs⁺/HMor) which were modified by CuO and Cs⁺. The FR spectra of ethene in HMor, CuO/HMor and Cs⁺/HMor were recorded at temperatures between 252 and 273K under the pressure of 0.2–30.0Torr, and then those FR spectra were investigated. The results showed that two parallel adsorption processes exist in ethene/HMor system. Those two processes were attributed to adsorption process of ethene on proton acid sites (low frequency adsorption) and on hydrogen cation sites (high frequency adsorption); meanwhile the number of sites available for adsorption of ethene is 0.692 and 0.828mmolg⁻¹, respectively. The number of adsorption sites in low frequency is increased by the introduction of CuO which is located among the proton acid sites but covered the hydrogen ion sites in high frequency. Chemical adsorption of ethene is the main sorption process in CuO/HMor. The number of adsorption sites in low frequency is decreased by the introduction of Cs⁺ which counteracted proton acid sites in low frequency. Physical adsorption is the main sorption process in Cs⁺/HMor channels. The optimum content of CuO for modification is 5% (weight/weight). Combining the FR spectra and other methods such as isotherms and Langmuir model, a thorough understanding of the ethene adsorption processes on zeolites can be achieved.

Keywords: Frequency response; Ethene; Mordenite; Adsorption sites; Dynamic parameter

Investigation of the Shockley surface state on clean and air-exposed Au (111) by P.J. Kowalczyk; M. Puchalski; W. Kozłowski; P. Dąbrowski; Z. Klusek; W. Olejniczak (pp. 4572-4576).

Scanning tunneling microscopy (STM) and spectroscopy (STS) carried out in vacuum and air were used to study the electronic structure of the Au (111) surface in the range of 0.0–0.7eV below the Fermi level. The STS experiment carried out in UHV showed the existence of the Shockley surface state (SS) located 0.48eV below the Fermi level. STS carried out in air showed strong local maximum located 0.35eV below the Fermi level. This maximum was ascribed to the SS shifted toward lower energy due to carbon and oxygen overlayer. To confirm that the SS could exist on the sample exposed to air we did ultraviolet photoemission spectroscopy (UPS) experiment on air-treated and clean Au (111). Our results suggest that the SS position initially measured at 0.38eV below the Fermi level was shifted to 0.27eV after air treatment. Additionally, the level of contamination was measured using X-ray photoelectron spectroscopy (XPS).

Keywords: PACS; 68.37.Ef; 79.60.−i; 73.20.AtSTS; UPS; Gold; Surface states; Air treatment

Electrophoreted Zn–TiO₂–ZnO nanocomposite coating films for photocatalytic degradation of 2-chlorophenol by A. Abdel Aal; M.A. Barakat; R.M. Mohamed (pp. 4577-4583).

TiO₂–ZnO nano-powders with different TiO₂/ZnO ratios have been synthesized by hydrothermal method. Nanocomposite coating films consisting of TiO₂–ZnO and Zn with thickness of 20μm have been electrophoreted on steel plates by rapid plating from a ZnO-based alkaline bath. X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis were used to investigate the structure, the size distribution, and the composition of prepared nano-powders and plated materials. The effect of the operating parameters such as powder contents, pH and current density on the electrophoresis process has been investigated and optimum conditions of coating process were determined. Corrosion properties of plated samples have been studied by salt spray test. The catalytic activity of the prepared nanocomposite Zn–TiO₂–ZnO films for the photocatalytic degradation of 2-chlorophenol (2-CP) was measured.

Keywords: Nano-powders; Electrophoresis; Composite coatings; Thin films; Chlorophenol; Photocatalysts

Titanium metallization of alumina ceramics by molten salt reaction by Jianqiang Li; Wei Pan; Zhangfu Yuan; Yunfa Chen (pp. 4584-4590).

In this work, we reported a novel method that is flexible to metallize alumina ceramics with complex surface. Through Ti²⁺ disproportionation occurred in molten NaCl–KCl–K₂TiF₆ bath, the dense Ti layer was deposited on Al₂O₃ ceramics surface with strong adhesion. The effects of reaction temperature, time and initial K₂TiF₆ concentration on deposition rate were investigated. As-prepared coatings compose of bilayer structure of reactive Ti₂O phase, namely, the outer layer with coarse grains and the inner layer with fine grains. The wettability of eutectic Ag72Cu28 and Pb37Sn63 alloys with metallized Al₂O₃ ceramics was measured by using sessile drop method and compared with that of original ceramics. The results show that the metallized Al₂O₃ surface could be reactively wetted well with Ag72Cu28 and Pb37Sn63 alloys. The contact angles lowered to 35° and 8°, respectively, when temperature rose to 900°C, showing significant enhancement of wettability after Ti metallization by molten salt reaction.

Keywords: PACS; 68.08.BcCoating; Ti; Alumina; Brazing; Wetting

Influence of Si/SiO₂ interface properties on electrical performance and breakdown characteristics of ultrathin stacked oxide/nitride dielectric films by Yi-Mu Lee; Yider Wu (pp. 4591-4598).

In this work, the influence of Si/SiO₂ interface properties, interface nitridation and remote-plasma-assisted oxidation (RPAO) thickness (<1nm), on electrical performance and TDDB characteristics of sub-2nm stacked oxide/nitride gate dielectrics has been investigated using a constant voltage stress (CVS). It is demonstrated that interfacial plasma nitridation improves the breakdown and electrical characteristics. In the case of PMOSFETs stressed in accumulation, interface nitridation suppresses the hole traps at the Si/SiO₂ interface evidenced by less negative V_t shifts. Interface nitridation also retards hole tunneling between the gate and drain, resulting in reduced off-state drain leakage. In addition, the RPAO thickness of stacked gate dielectrics shows a profound effect in device performance and TDDB reliability. Also, it is demonstrated that TDDB characteristics are improved for both PMOS and NMOS devices with the 0.6nm-RPAO layer using Weibull analysis. The maximum operating voltage is projected to be improved by 0.3V difference for a 10-year lifetime. However, physical breakdown mechanism and effective defect radius during stress appear to be independent of RPAO thickness from the observation of the Weibull slopes. A correlation between trap generation and dielectric thickness changes based on the C– V distortion and oxide thinning model is presented to clarify the trapping behavior in the RPAO and bulk nitride layer during CVS stress.

Keywords: Oxide/nitride dielectric; Si/SiO; ₂; interface; Interface nitridation; RPAO; Dielectric breakdown; Weibull distribution; TDDB reliability

An XPS study on the attachment of triethoxsilylbutyraldehyde to two titanium surfaces as a way to bond chitosan by Holly J. Martin; Kirk H. Schulz; Joel D. Bumgardner; Keisha B. Walters (pp. 4599-4605).

A bioactive coating has the ability to create a strong interface between bone tissue and implant. Chitosan, a biopolymer derived from the exoskeletons of shellfish, exhibits many bioactive properties that make it an ideal material for use as a coating such as antibacterial, biodegradable, non-toxic, and the ability to attract and promote bone cell growth and organized bone formation. A previous study reported on the bonding of chitosan to a titanium surface using a three-step process. In the current study, 86.4% de-acetylated chitosan coatings were bound to implant quality titanium in a two-step process that involved the deposition of triethoxsilylbutyraldehyde (TESBA) in toluene, followed by a reaction between the aldehyde of TESBA with chitosan. The chitosan coatings were examined on two different metal treatments to determine if any major differences in the ability of titanium to bind chitosan could be detected. The surface of the titanium metal and the individual reaction steps were examined using X-ray photoelectron spectroscopy (XPS). Following the deposition of TESBA, significant changes were seen in the amounts of oxygen, silicon, carbon, and titanium present on the titanium surface, which were consistent with the anticipated reaction steps. It was demonstrated that more TESBA was bound to the piranha-treated titanium surface as compared to the passivated titanium surface. The two different silane molecules, aminopropyltriethoxysilane (APTES) and TESBA, did not affect the chemistry of the resultant chitosan films. XPS showed that both the formation of unwanted polysiloxanes and the removal of the reactive terminal groups were prevented by using toluene as the carrier solvent to bond TESBA to the titanium surfaces, instead of an aqueous solvent. Qualitatively, the chitosan films demonstrated improved adhesion after using toluene, as the films remained attached to the titanium surface even when placed under the ultra-high vacuum necessary for XPS, unlike the chitosan films deposited using an aqueous solvent, which were removed when exposed to the ultra-high vacuum environment of XPS.

Keywords: Biopolymer; Chitosan; XPS; Biomedical coatings; Triethoxsilylbutyraldehyde

A simple swelling and anchoring method for preparing dense and stable poly(ethylene oxide) layers on polystyrene surfaces by Yanlei Su; Lijun Wang; Xinjing Yang (pp. 4606-4610).

In order to obtain dense and stable poly(ethylene oxide) (PEO) layers for reducing protein adsorption, polystyrene (PS) plates were first soaked in chloroform/methanol mixed organic solvent to swell the polymer. The swelled PS plates were then immersed into Pluronic F127 (amphiphilic block copolymer) aqueous solution, Pluronic F127 molecules were adsorbed favorably on the swelled PS surfaces. After evaporation of organic solvent, the adsorbed Pluronic F127 molecules were trapped and anchored permanently on the PS substrates. The dense and stable PEO layers anchored on the PS surfaces can effectively inhibit protein adsorption.

Keywords: Polystyrene; Pluronic F127; Swelling; Anchoring; Antifouling

Formation of uniform self-assembly monolayers by choosing the right solvent: OTS on silicon wafer, a case study by Touraj Manifar; Asad Rezaee; Mehdi Sheikhzadeh; Silvia Mittler (pp. 4611-4619).

The main purpose of this research is to show the effects of solvent nature, partial charge distribution and polarity index, on the preparation of uniform silane self-assembly monolayers. Octadecyltrichlorosilane (OTS) on silicon wafers was chosen as a case study. Contrary to what was thought before, dipole moment data are not enough and one needs accompanying data on partial charge distribution and polarity index to predict the best solvent for a uniform self-assembled monolayer (SAM). Results can be applied to other monolayer-solvent systems.

Keywords: Self-assembled monolayer; SAM; Gold deposition; Nanoparticles; Solvent screening; OTS; Silicon wafer; Partial charge distribution; Polarity index

Visible-light photocatalytic activity of nitrogen-doped TiO₂ thin film prepared by pulsed laser deposition by Lei Zhao; Qing Jiang; Jianshe Lian (pp. 4620-4625).

Nitrogen-doped titanium dioxide (TiO2−_xN_x) thin films have been prepared by pulse laser deposition on quartz glass substrates by ablated titanium dioxide (rutile) target in nitrogen atmosphere. The x value (nitrogen concentration) is 0.567 as determined by X-ray photoelectron spectroscopy measurements. UV–vis spectroscopy measurements revealed two characteristic deep levels located at 1.0 and 2.5eV below the conduction band. The 1.0eV level is attributable to the O vacancy state and the 2.5eV level is introduced by N doping, which contributes to narrowing the band-gap by mixing with the O2p valence band. The enhanced degradation efficiency in a broad visible-light range was observed from the degradation of methylene blue and methylene orange by the TiO2−_xN_x film.

Keywords: Visible-light photocatalytic activity; TiO; ₂; thin film; Nitrogen-doped; Pulsed laser deposition

Optical transitions of InAs/In_0.36Ga_0.64As/GaAs(311B) surface quantum dots clearly identified by the piezoreflectance technique by C. Wang; Y. Yang; X.M. Chen; Z.L. Liu; H.Y. Cui; S. Zhang; X.S. Chen; W. Lu (pp. 4626-4631).

The bilayer InAs/In_0.36Ga_0.64As/GaAs(311B) quantum dots (QDs), including one InAs buried quantum dot (BQD) layer and the other InAs surface quantum dot (SQD) layer, have been grown by molecular beam epitaxy (MBE). The optical properties of these three samples have been studied by the piezoreflectance (PzR) spectroscopy. The PzR spectra do not exhibit only the optical transitions originated from the InAs BQDs, but the features originated from the InAs SQDs. After the InAs SQDs have been removed chemically, those optical transitions from InAs SQDs have been demonstrated clearly by investigating the PzR spectra of the residual InAs BQDs in these samples. The great redshift of these interband transitions of InAs SQDs has been well discussed. Due to the suitable InAs SQD sizes and the thickness of In_0.36Ga_0.64As layer, the interband transition of InAs SQDs has been shifted to ∼1.55μm at 77K.

Keywords: Surface quantum dots; Molecular beam epitaxy; Photoluminescence; Piezoreflectance spectroscopy

Correlation between optical characterization of the plasma in reactive magnetron sputtering deposition of Zr–N on SS 316L and surface and mechanical properties of the deposited films by A. Fragiel; R. Machorro; J. Muñoz-Saldaña; J. Salinas; L. Cota (pp. 4632-4637).

Optical and surface spectroscopies as well as nanoindentation techniques have been used to study ZrN coatings on 316L stainless steel obtained by DC-reactive magnetron sputtering. The deposit process was carried out using initial and working pressures of 10⁻⁶Torr and 10⁻³Torr, respectively. The experimental set-up for optical spectra acquisition was designed for the study in situ of the plasma in the deposition chamber. Auger spectroscopy, SEM and X-ray diffraction were used to characterize the coatings. Nanoindentation tests were carried out to measure the mechanical properties of the coating. Plasma characterization revealed the presence of CN molecules and Cr ions in the plasma. Surface spectroscopy results showed that ZrN, Zr₃N₄ and ZrC coexist in the coating. These results allowed the understanding of the mechanical behavior of the coatings, demonstrating the importance of the plasma characterization as a tool for tailoring the properties of hard coatings.

Keywords: PACS; 62; 68.37.−d; 300.2140; 310.3840Plasma diagnostics; Auger spectroscopy; Nanoindentation; Thin films; Mechanical properties

The microstructure investigation of GeTi thin film used for non-volatile memory by Jie Shen; Bo Liu; Zhitang Song; Cheng Xu; Shuang Liang; Songlin Feng; Bomy Chen (pp. 4638-4643).

GeTi thin film has been found to have the reversible resistance switching property in our previous work. In this paper, the microstructure of this material with a given composition was investigated. The film was synthesized by magnetron sputtering and treated by the rapid temperature process. The results indicate a coexist status of amorphous and polycrystalline states in the as-deposited GeTi film, and the grains in the film are extremely fine. Furthermore, not until the film annealed at 600°C, can the polycrystalline state be detected by X-ray diffraction. Based on the morphological analysis, the sputtered GeTi has the column growth tendency, and the column structure vanishes with the temperature increasing. The microstructure and thermal property analysis indicate that GeTi does not undergo evident phase change process during the annealing process, which makes the switching mechanism of GeTi different from that of chalcogenide memory material, the most widely used phase change memory material.

Keywords: PACS; 68.55.−a; 81.40.−zGeTi; Magnetron sputtering; Microstructure; Reversible resistance switching

Surface characteristics of Ni catalystic films on growth behavior of multi-walled carbon nanotubes by Hoon-Sik Jang; Sung-Oong Kang; Seung-Hoon Nahm; Bae Ho Park; Yong-Il Kim (pp. 4644-4649).

The effect of the surface characteristics of Ni catalyst films on the growth behavior of multi-walled carbon nanotubes (MWCNTs) were investigated using Ni catalyst films prepared by different physical vapor deposition methods, electron-beam evaporation and sputtering. The growth behavior of MWCNTs was dependent upon the surface roughness of the Ni films. After a pretreatment process with NH₃, the root mean squares of surface roughness of e-beam evaporated and sputtered Ni catalyst films increased to 16.6 and 3.2nm, respectively. Curled-MWCNTs and carbon-encapsulated Ni nanoparticles were formed on the Ni film deposited by e-beam evaporation while vertically aligned-MWCNTs were grown on the sputter-deposited film. In addition, the surface roughness of the Ni films affected the field emission properties of the MWCNTs. This was considered to originate from the specific growth behavior of the MWCNTs which was primarily caused by the initial surface roughness of the Ni films.

Keywords: PACS; 68.37.Ps; 78.67.Ch; 79.70.+gCarbon nanotubes; Catalyst metal; Growth behavior

The effect of electro-annealing on the electrical properties of ITO film on colorless polyimide substrate by Dong-ho Lee; Shang-hun Shim; Jin-sik Choi; Keun-byoung Yoon (pp. 4650-4654).

The effect of different annealing methods on the sheet resistance of indium tin oxide (ITO) on polyimide (PI) substrate has been investigated. ITO thin films were prepared by RF magnetron sputtering in pure Ar gas and electro-annealing, this was carried out in the flow of an electric current at several temperatures between 100 and 180°C in air. Electro- and thermal annealing were compared in order to confirm differences between the electrical, optical and microstructural properties of the ITO thin films. As electro-annealing induced the predominant growth of crystallites of ITO thin films along (400) plane, the sheet resistance of ITO films that were electro-annealed for 2mA at 180°C considerably decreased from 50 to 28Ω/cm².

Keywords: ITO; Electro-annealing; Sheet resistance; Growth of crystallites; Transmittance

Photodegradation of CH₃I on mesoporous TiO₂-B nanofibers with Au nanoparticles by Jr-Sheng Li; Dong-Lin Shieh; Dian-Yi Li; Chia-Hsun Ho; Shang-Ju Yang; Jong-Liang Lin (pp. 4655-4664).

Au nanoparticles deposited on mesoporous TiO₂-B nanofibers have been prepared, characterized, and used to catalyze photoreactions of iodomethane. High-density gold-particle deposition on TiO₂-B is obtained by electrostatic and/or chemical force between the particles of TiO₂-B and Au capped with –SC(H)(CO₂H)(CH₂CO₂H) through pH control. The capping groups on the gold particles can be removed after 400°C calcination. It is found that the nature of the inorganic acids used for pH adjustment has effects on particle morphology and deposition. Two other methods, i.e., preparation of TiO₂-B nanofibers in the presence of gold particles and preparation of gold nanoparticles in the presence of TiO₂-B particles (deposition–precipitation method), are also investigated. However, the former method produces a low-density deposition and the latter one induces a morphology change of the TiO₂-B and an increase of the Au in size. Fourier transform infrared spectroscopy has been employed to study and to compare the photoreactions of CH₃I on TiO₂-B and Au/TiO₂-B and the effect of O₂. The presence of gold particles on TiO₂-B increases the efficiency of CH₃I photodegradation, forming adsorbed methoxy and formate. The role of gold is also discussed.

Keywords: TiO; ₂; -B; CH; ₃; I; Au; Photochemistry

Composition and local bonding in RE–Si–M–O–N (M=Mg, Al ;RE=La, Lu) glasses by V. Fouquet-Parry; F. Paumier; M.J. Guittet; M. Gautier-Soyer; R. Satet; M.J. Hoffmann; P.F. Becher; G.S. Painter (pp. 4665-4670).

Two series of oxynitride glasses, RE–Si–Mg–O–N (M=Mg, Al ;RE=La, Lu), have been studied by X-Ray photoelectron spectroscopy (XPS). The oxygen 1s photoelectron lineshape reveals a striking difference depending on the rare earth, both in the Mg series and in the Al series. Specifically, the oxygen 1s photoelectron lines of the La doped glasses are broader than the ones of the Lu doped glasses. This result is an experimental evidence that Lu has a larger affinity for oxygen versus nitrogen than La, as theoretically predicted by the first-principles calculations by Painter et al.

Keywords: PACS; 79.60.-i; 61.43.Fs; 71.23.Cq; 82.80.PvXPS; Binding energy; Oxynitride glass; Rare earths

Electron Energy Loss Spectroscopy study of the near surface region of the ternary Co–Cr–Mo alloy by M.A. Vasylyev; V.A. Tinkov; P.A. Gurin (pp. 4671-4680).

Nature of the characteristic electron energy losses in the second electron emission spectra from the ternary Co–Cr–Mo alloy surface are studied in the low energy range of the primary electron energy E₀. The main types of losses were found: surface and bulk plasmons and their hybrid modes, interband transitions and ionization losses. For Co, Cr, Mo and Co–Cr–Mo alloy the experimental values of the plasmon energy were established to be less than it was predicted by free-electron gas model. Excess of conductive electrons in the surface layers for Co, Cr and Mo was observed by dependence of the surface plasmon dispersion from E₀, while for Co–Cr–Mo alloy the situation is quit opposite. Such behavior is explained by the complex phase structure of the ternary alloy. The analysis of intensity lines of plasmons from E₀ showed deeply changed alloy profile. Ionization Spectroscopy was used for studying the alloy elements distributing on the depth. Mo atoms preferred segregation in the outermost layers of Co–Cr–Mo alloy and enrichment with Cr competitive atoms in underlayers is displayed.

Keywords: PACS; 79.20.H; 34.50.F; 71; 45.G; 73.20.M; 64.75Co–Cr–Mo alloy; Electron Energy Loss Spectroscopy (EELS); Surface and bulk plasmons; Interband transitions; Ionization losses; Surface segregation

Temperature and substrate dependence of structure and growth mechanism of carbon nanofiber by Chia-Chih Chuang; Wei-Long Liu; Wen-Jauh Chen; Jin-Hua Huang (pp. 4681-4687).

The carbon nanofibers were grown on Ni/Si and Ni/Ti/Si substrates in 1atm CH₄ atmosphere at 640°C and 700°C by thermal chemical vapor deposition method. The carbon nanofibers were characterized by field emission scanning electron microscopy, transmission electron microscopy, and Raman spectrometry for morphology, microstructure, and crystallinity. The electron emission property of carbon nanofibers was also investigated by current–voltage ( I– V) measurement. The results showed that the solid amorphous carbon nanofibers could be grown on Ni/Si substrate at 640°C through tip growth mechanism, the carbon nanotubes could be grown on Ni/Si substrate at 700°C through tip growth mechanism, and the carbon nanotubes could be grown on Ni/Ti/Si substrate at 700°C through root growth mechanism.

Keywords: Carbon nanofiber; Carbon nanotube; Amorphous; Growth mechanism; Thermal chemical vapor deposition

Cobalt sorption properties of MgO prepared by solution combustion by F. Granados-Correa; J. Bonifacio-Martínez; V.H. Lara; P. Bosch; S. Bulbulian (pp. 4688-4694).

Water effect on the combustion preparation of MgO is presented. The obtained materials are characterized through their specific surface area, morphology, particle shape, fractal dimension and Co²⁺ sorption. The surface fractal dimension of the combustion prepared sample was 2.0 but in those where water was included it decreased to 1.8. In the sample prepared by calcination it was 2.3. A linear correlation between the fractal dimension and Co²⁺ sorption was found.

Keywords: Magnesium oxide; Solution combustion method; Surface properties; Fractal dimension; Cobalt sorption

Formation of nano-hillocks by impact of swift heavy ions on thin films of TiO₂ by Madhavi Thakurdesai; D. Kanjilal; Varsha Bhattacharyya (pp. 4695-4700).

Amorphous thin films of TiO₂ are irradiated by swift heavy ion (SHI) beam. Surface topography is studied by atomic force microscopy (AFM). Formation of nanosized oblate hillocks on the surface of irradiated films is investigated by AFM studies. After irradiation, amorphous to crystalline phase transition is observed in glancing angle X-ray diffraction (GAXRD) and Raman spectroscopy studies. Photoluminescence (PL)-spectroscopy is carried out for optical characterization. Threshold value necessary for emergence of hillocks is estimated.

Keywords: PACS; 61.80.Jh; 61.82.Rx; 68.37.Ps; 78.30.−j; 78.55.−mSwift heavy ion; Nanodimensional TiO; ₂; AFM; Raman spectroscopy; Photoluminescence

Effects of CeO₂-ZrO₂ present in Pd/Al₂O₃ catalysts on the redox behavior of PdO_x and their combustion activity by Renxian Zhou; Bo Zhao; Baohua Yue (pp. 4701-4707).

The ceria-zirconium-modified alumina-supported palladium catalysts are prepared using impregnation method with H₂PdCl₄ as Pd source, hydrazine hydrate as reducing agent. The physicochemical properties of these catalysts are characterized by BET surface area (BET), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), temperature programmed reduction (H₂-TPR) and temperature programmed oxidation (O₂-TPO) techniques, and their catalytic activities for the combustion of methane are examined. The results show that the palladium mainly exist in a highly dispersed PdO species on Ce-Zr-rich grains as well as Al₂O₃-rich grains surfaces, and a stable PdO species due to the strong interaction between PdO and CeO₂-ZrO₂ on the Ce-Zr/Al₂O₃ surfaces. The catalytic activity is strongly related to the redox behavior of PdO species highly dispersed on Ce-Zr-rich grains and Al₂O₃-rich grains surfaces, and the higher the reducibility of the PdO species, the higher the catalytic activity. The presence of Ce-Zr in Pd/Al₂O₃ catalyst would inhibit the site growth of PdO_x particles and decomposition of PdO to Pd⁰, and the reoxidation property of Pd⁰ to PdO_x is significantly improved, which obviously increases thermal stability and catalytic activity of Pd/Ce-Zr/Al₂O₃ catalyst for the methane combustion.

Keywords: Pd/Ce-Zr/Al; ₂; O; ₃; catalysts; Methane combustion; Oxidation–reduction properties

Preparation, characterization and microwave absorption properties of electroless Ni–Co–P-coated SiC powder by Yongjie Li; Rui Wang; Fengming Qi; Chunming Wang (pp. 4708-4715).

Silicon carbide particles reinforced nickel–cobalt–phosphorus matrix composite coatings were prepared by two-step electroless plating process (pre-treatment of sensitizing and subsequent plating) for the application to lightweight microwave absorbers, which were characterized by scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), vibrating sample magnetometer (VSM) and vector network analyzer, respectively. The results show that Ni–Co–P deposits are uniform and mixture crystalline of α-Co and Ni₃P and exhibit low-specific saturation magnetization and low coercivity. Due to the conductive and ferromagnetic behavior of the Ni–Co thin films, high dielectric constant and magnetic loss can be obtained in the microwave frequencies. The maximum microwave loss of the composite powder less than −32dB was found at the frequency of 6.30GHz with a thickness of 2.5mm when the initial atomic ratio of Ni–Co in the plating bath is 1.5.

Keywords: PACS; 41.20.Gz; 61.10.Nz; 68.37.Hk; 78.40.−qSilicon carbide; Microstructure; Complex relative dielectric permittivity; Complex relative magnetic permeability; Reflection loss

Synthesis of GaN nanowires by Tb catalysis by Jinhua Chen; Chengshan Xue; Huizhao Zhuang; Lixia Qin; Hong Li; Zhaozhu Yang (pp. 4716-4719).

Rare earth metal seed Tb was employed as catalyst for the growth of GaN wires. GaN nanowires were synthesized successfully through ammoniating Ga₂O₃/Tb films sputtered on Si(111) substrates. The samples characterization by X-ray diffraction and Fourier transform infrared indicated that the nanowires are constituted of hexagonal wurtzite GaN. Scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy showed that the samples are single-crystal GaN nanowire structures. The growth mechanism of the GaN nanowires is discussed.

Keywords: PACS; 68.65.−k; 78.30.Fs; 81.16.−cGaN; Nanowires; Sputtering; Single-crystal growth

Hydrolysis and stability of thin pulsed plasma polymerised maleic anhydride coatings by Joanna Drews; Helene Launay; Charles M. Hansen; Keld West; Søren Hvilsted; Peter Kingshott; Kristoffer Almdal (pp. 4720-4725).

The stability of plasma polymerised layers has become important because of their widespread use. This study explored the hydrolysis and degradation stability of coatings of plasma polymerised maleic anhydride. Coatings made with different plasma parameters were exposed to aqueous media of different pH as a function of time. ATR-FTIR was used for structure analysis and a toluidine blue staining method allowed quantitative analysis of the hydrolysis of anhydride groups to acid groups. Coatings with constant thickness were obtained at different plasma powers and layers with varying thickness were obtained at constant plasma power by adjusting the polymerisation time. The results show that the hydrolysis resistance of the modified layer is determined by the power used in the plasma polymerisation, while changes in the chemistry of the modified layer are insignificant.

Keywords: PACS; 81.65.−b; 82.33.Xj; 52.77.−jMaleic anhydride; Coatings; AC plasma; Cross-linking; Swelling

Visible-light-driven titania photocatalyst co-doped with nitrogen and ferrum by Xiang-Zhong Shen; Jun Guo; Zhi-Cheng Liu; Shan-Mei Xie (pp. 4726-4731).

Nitrogen and ferrum co-doped titania photocatalyst was prepared by the sol–gel route. The prepared photocatalyst was characterized by various techniques including X-ray diffraction (XRD), UV–vis diffusive reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption–desorption isotherm. The photocatalytic activity of the co-doped titania photocatalyst was evaluated by the degradation of methyl orange (MO) from aqueous solution under visible light irradiation and was compared with that of the commercial TiO₂ photocatalyst (Degussa P25). The results revealed that the nitrogen doping could lead to the response to visible light and that the ferrum doping could improve the photocatalytic performance. The effects of the component and the annealing temperature of the co-doped titania photocatalyst on the photocatalytic activity were investigated.

Keywords: Titania; Co-doping; Photocatalysis; Visible light degradation; Methyl orange

Surface-modified mesoporous silica with ferrocene derivatives and its ultrasound-triggered functionality by Eun Jung Kwon; Tai Gyu Lee (pp. 4732-4737).

Novel ferrocene derivatives designed as gatekeepers were successfully composed on the pore outlet of amino-functionalized mesoporous silica by post-synthesis grafting where the peptide bond of the amine group (–NH₂) of mesoporous silica was linked with the carboxylic acid group (–COOH) of both ends of the ferrocene derivatives. The materials of the amine-functionalized mesoporous silica (NH₂–MS) and ferrocene-functionalized mesoporous silica (Fc–CONH–MS) were characterized using X-ray diffractions (XRD), Fourier-transform infrared (FT-IR), N₂ sorption isotherms, solid-state NMR spectra, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), and UV–vis absorption spectra. The ferrocene attached to the mesoporous silica pore outlet was cleavaged by ultrasound irradiation, which opened the closed-pore outlets, suggesting a possible application for controlled release drug carrier.

Keywords: PACS; 61.66.Fn; 81.07.PrMesoporous silica; Ferrocene; Surface modification; Ultrasound; Controlled release system

A study of the 42CrMo4 steel surface by quantitative XPS electron spectroscopy by M. Flori; B. Gruzza; L. Bideux; G. Monier; C. Robert-Goumet (pp. 4738-4743).

Quantitative X-ray photoelectron spectroscopy was used to characterize the native oxide film formed on 42CrMo4 steel surface by air exposure in normal conditions. In order to determine the thickness and composition of the oxide layer we have used a stacking layer model together with experimental XPS sputtering depth profiling. At a nanoscale study, to obtain quantitative results one must take into account fundamental parameters like the attenuation depth of photoelectrons. We have found that both lepidocrocit (γ-FeOOH) and magnetite (Fe₃O₄) were present and the total thickness of the oxide layer was 16monolayers.

Keywords: Steel; Iron oxide; X-ray photoelectron spectroscopy; Argon ion sputtering; Depth profiling

Enhancement of the hydrophobicity of silk fabrics by SF₆ plasma by Satreerat K. Hodak; T. Supasai; B. Paosawatyanyong; K. Kamlangkla; V. Pavarajarn (pp. 4744-4749).

Hydrophobic properties are of interest in fabric and textile manufacture. We have used radio-frequency inductively coupled SF₆plasma to modify the surface of Thai silk fabrics for the enhancement of the hydrophobic property. The water contact angle of fabrics increased from 0°up to 145°after SF₆ plasma treatment. The measured water absorption time was found to depend upon the treatment time and RF power, for SF₆ pressures lower than 0.05Torr. At higher SF₆ pressures, all samples achieved absorption times in excess of 200min, regardless of the treatment time and RF power. The morphology changes of fabrics after plasma treatment were characterized by scanning electron microscopy and atomic force microscopy. After plasma treatment, the RMS surface roughness of the fibres increased from about 10 to 30nm. From X-ray photoelectron microscopy analysis, we found that the hydrophobicity of the fabrics is the highest when the fluorine/carbon ratio at the surface increases. A small decrease of the oxygen/carbon ratio was also observed on the fabrics that showed the longest absorption times.

Keywords: SF; ₆; plasma; Thai silk; HydrophobicityPACS; 52.77.Dq

DNA hybridization and phosphinothricin acetyltransferase gene sequence detection based on zirconia/nanogold film modified electrode by Wei Zhang; Tao Yang; Chen Jiang; Kui Jiao (pp. 4750-4756).

This study reports a novel electrochemical DNA biosensor based on zirconia (ZrO₂) and gold nanoparticles (NG) film modified glassy carbon electrode (GCE). NG was electrodeposited onto the glassy carbon electrode at 1.5V, and then zirconia thin film on the NG/GCE was fabricated by cyclic voltammetric method (CV) in an aqueous electrolyte of ZrOCl₂ and KCl at a scan rate of 20mV/s. DNA probes were attached onto the ZrO₂/NG/GCE due to the strong binding of the phosphate group of DNA with the zirconia film and the excellent biocompatibility of nanogold with DNA. CV and electrochemical impedance spectroscopy (EIS) were used to characterize the modification of the electrode and the probe DNA immobilization. The electrochemical response of the DNA hybridization was measured by differential pulse voltammetry (DPV) using methylene blue (MB) as the electroactive indicator. After the hybridization of DNA probe (ssDNA) with the complementary DNA (cDNA), the cathodic peak current of MB decreased obviously. The difference of the cathodic peak currents of MB between before and after the hybridization of the probe DNA was used as the signal for the detection of the target DNA. The sequence-specific DNA of phosphinothricin acetyltransferase (PAT) gene in the transgenic plants was detected with a detection range from 1.0×10⁻¹⁰ to 1.0×10⁻⁶mol/L, and a detection limit of 3.1×10⁻¹¹mol/L.

Keywords: Zirconia; Gold nanoparticles; DNA sensor; Phosphinothricin acetyltransferase gene; Electrochemical detection

Application of spectroscopic photoemission and low energy electron microscope to high- k gate dielectrics: Relationship between surface morphology and electronic states during Hf-silicide formation by R. Yasuhara; T. Taniuchi; H. Kumigashira; M. Oshima; F. Guo; T. Kinoshita; K. Ono; K. Ikeda; G.-L. Liu; Z. Liu; K. Usuda (pp. 4757-4761).

We have applied the spectroscopic photoemission and low energy electron microscope to study high- k gate dielectrics and have performed the following in situ operations during ultrahigh vacuum annealing: real-time observation of surface morphology and microregion photoelectron spectroscopy measurements. Changes in surface morphology and electronic states were consistent with the models previously reported in the case of HfO₂/Si. No clear differences between void regions and nonvoid regions have been observed in microregion photoelectron spectra for poly-Si/HfO₂/Si, regardless of phase separation in real space. These results have suggested that the initial void formation occurs in about 100-nm wide regions for both HfO₂/Si and poly-Si/HfO₂/Si.

Keywords: High-; k; gate dielectrics; Vacuum annealing; PEEM; Electronic states; Microregion photoelectron spectroscopy

Surface flatness of optical thin films evaluated by gray level co-occurrence matrix and entropy by Chuen-Lin Tien; You-Ru Lyu; Shiao-Shan Jyu (pp. 4762-4767).

The surface characteristics of titanium oxide films evaluated by gray level co-occurrence matrices (GLCMs) and entropy are demonstrated experimentally. A PC-based measurement system was set up to detect the interference fringe of optical coating surface as captured by a Fizeau interferometer. Titanium oxide films were prepared by an electron-beam gun evaporation method. The proposed measuring system was used to evaluate the surface flatness of titanium oxide films coated on glass substrates. The variation of entropy in titanium oxide films before and after film deposition was found to be related to the root-mean-square (rms) surface roughness. Surface characteristics of thin films were fast measured by our proposed method and the test results were verified by atomic force microscopy (AFM) and scanning electrical microscopy (SEM).

Keywords: PACS; 68.55.−a; 42.79.Wc ;77.55.+fThin film; Surface flatness; Gray level co-occurrence matrix; Entropy

Utilization of TXRF analytical technique in order to improve front-end semiconductor processing by Thanas Budri (pp. 4768-4773).

In this paper, we summarize how the introduction of in-line TXRF monitoring provides detailed analytical information on aluminum, titanium and molybdenum contamination levels in order to improve several process steps from front-end processing, minimize product yield loss and make it possible to successfully manufacture multiple products and process geometries in the same fabrication platform.

Keywords: TXRF; SIMS; ToF-SIMS; EMMI (emission spectroscopy; delamination overheating metallization layers material characterization technique); Front-end or FEOL (processing of semiconductor wafers till metal layer1 in order to test the transistors performance via electrical testing); Back-end or BEOL (additional processing where interconnect and insulators are added to complete circuitry prior to wafer dicing and packaging); Pad etch window (window opening for contact via plasma etch); Contamination

Molecular dynamics simulation of subsurface deformed layers in AFM-based nanometric cutting process by J.J. Zhang; T. Sun; Y.D. Yan; Y.C. Liang; S. Dong (pp. 4774-4779).

Three-dimensional molecular dynamics simulations of AFM-based nanometric cutting monocrystalline copper with pin tool radius of 0.713nm are performed to investigate the effect of uncut chip thicknesses (0.1805nm, 0.361nm, 0.5415nm, 0.722nm, 0.9025nm, 1.0875nm, and 1.268nm) on the depth of subsurface deformed layers. The EAM potential and Morse potential are utilized respectively to compute the interactions between workpiece atoms, the interactions between workpiece atoms and tool atoms. The single-atom potential energy variations of the workpiece atoms within the subsurface regions during the cutting process are obtained and analyzed through a deformation criterion to determine the deformation behaviors of subsurface atoms. The simulation results reveal that the depth of subsurface deformed layers is affected by the AFM pin tool's rake angle. At each uncut chip thickness, the AFM pin tool presents different negative rake angles, consequently different degrees of deformation in the subsurface take place.

Keywords: Nanometric cutting; AFM; Molecular dynamics; Subsurface deformed layers; Deformation criterion

Visible-light-induced degradation of formaldehyde over titania photocatalyst co-doped with nitrogen and nickel by Xin Zhang; Qingquan Liu (pp. 4780-4785).

Titanium isopropoxide, ammonium carbonate and nickelous nitrate were used as the sources of titanium, nitrogen, and nickel to prepare titania photocatalyst co-doped with nitrogen and nickel by means of the modified sol–gel method. The photocatalyst was characterized by X-ray diffraction (XRD), UV–vis diffusive reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM). The prepared N-Ni co-doped photocatalyst showed optical absorption in the visible light area and exhibited excellent photocatalytic ability for the degradation of formaldehyde under visible light irradiation. The effects of annealing temperature and component on the phase composition and photocatalytic activity were investigated. The results demonstrated that nitrogen atoms was weaved into the structure of titania and led to the response to visible light. However, nickel atoms existed in the form of Ni₂O₃, dispersed on the surface of TiO₂, suppressed the recombination of photo-induced electron-hole pairs, raised the photo quantum efficiency, and led to the enhancement of photocatalytic performance. The increase of photoactivity was attributed to the synergistic effects of co-doping.

Keywords: Nitrogen; Nickel; Co-doping; Titania photocatalysis; Visible light; Formaldehyde

Influence of Si-N interlayer on the microstructure and magnetic properties of γ′-Fe₄N films by N. Ma; X. Wang; W.T. Zheng; L.L. Wang; M.W. Wang; P.J. Cao; X.C. Ma (pp. 4786-4792).

The (γ′-Fe₄N/Si-N)_n ( n: number of layers) multilayer films and γ′-Fe₄N single layer film synthesized on Si (100) substrates by direct current magnetron sputtering were annealed at different temperatures. The structures and magnetic properties of as-deposited films and films annealed at different temperatures were characterized using X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. The results showed that the insertion of Si-N layer had a significant influence on the structures and magnetic properties of γ′-Fe₄N film. Without the addition of Si-N lamination, the iron nitride γ′-Fe₄N tended to transform to α-Fe when annealed at the temperatures over 300°C. However, the phase transition from γ′-Fe₄N to ɛ-Fe₃N occurred at annealing temperature of 300°C for the multilayer films. Furthermore, with increasing annealing temperature up to 400°C or above, ɛ-Fe₃N transformed back into γ′-Fe₄N. The magnetic investigations indicated that coercivity of magnetic phase γ′-Fe₄N for as-deposited films decreased from 152Oe (for single layer) to 57.23Oe with increasing n up to 30. For the annealed multilayer films, the coercivity values decreased with increasing annealing temperature, except that the film annealed at 300°C due to the appearance of phase ɛ-Fe₃N.

Keywords: (γ′-Fe; ₄; N/Si-N); _n; multilayer film; Phase transition; Magnetic properties

UV-curable nanoimprint resin with enhanced anti-sticking property by Joo Yeon Kim; Dae-Geun Choi; Jun-Ho Jeong; Eung-Sug Lee (pp. 4793-4796).

This paper reports on a newly developed anti-sticking resin obtained by mixing a fluorine-containing monomer (F-monomer) for UV nanoimprinting lithography (UV-NIL) to reduce the contact adhesion force during the demolding process. The new resin system shows an enhanced reliability and resolution of pattern transfer with no treatment on the surface of the quartz stamp. We fabricated various nanopatterns with F-monomer resins of various concentrations in the low pressure UV-NIL. The number of process steps of a release layer treatment for UV-NIL was reduced by using F-monomer with anti-sticking property.

Keywords: UV nanoimprinting lithography (UV-NIL); Micro- and nano-scale pattern; Anti-sticking layer

Stability and characterization of mesoporous molecular sieve using natural clay as a raw material obtained by microwave irradiation by Tingshun Jiang; Wei Shen; Yajing Tang; Qian Zhao; Mei Li; Hengbo Yin (pp. 4797-4802).

Mesoporous molecular sieve was synthesized via microwave irradiation method, and using natural clay, sodium silicate and aluminum chloride as raw materials and cetyl trimethyl ammonium bromide (CTAB) as a template agent under alkaline condition. The samples were characterized by various analytic and spectroscopic tools such as XRD, FT-IR, TEM, TG-DSC and N₂ physical adsorption, respectively. The results show that the synthesized sample has typical mesoporous structure and exhibits good mesoporous ordering. On the other hand, the as synthesized sample after calcination at 550°C for 10h has a surface area of 576.0m²/g and an average pore size of 4.83nm. Furthermore, the synthesized mesoporous molecular sieve still exhibits good mesoporous ordering after calcination at 750°C for 3h or hydrothermal treatment at 100°C for 10 days.

Keywords: Natural clay; Microwave irradiation; Mesoporous molecular sieve; Stability; Characterization

Raman spectroscopic studies of Pb_xLa1−_xTi1− x_/4O₃ thin films grown on Si substrates by RF magnetron sputtering by J.L. Zhu; W.L. Zhu; R.T. Li; W.Y. Ge; M. Jiang; J.G. Zhu; D.Q. Xiao; G. Pezzotti (pp. 4803-4807).

A systematic spectroscopic investigation of Pb_xLa1−_xTi1− x_/4O₃ (PLT) thin films grown on PbO_x/Pt/Ti/SiO₂/Si substrate by RF magnetron sputtering was performed by using confocal Raman spectroscopy. Influence of the growth condition modification including different growth temperatures, with various buffer layer thickness, and post-annealing treatments were analyzed with taking advantages of the corresponding Raman spectral band variation in the respective process. Significant change in the spectral bands occurred with the alteration of the growth condition, and the related mechanisms were discussed after spectral deconvolution, providing reliable information about the direction for film growth.

Keywords: PACS; 81.15.Cd; 87.64.Je; 68.55.JkRaman spectroscopy; Thin films; Lead titanate

Surface and transport studies on La_0.7Ba_0.3MnO₃:SnO₂ bilayer by J. Mona; Hitesh Mamgain; S. Jejurikar; R.R. Rawat; V. Ganesan; R.J. Choudhary; D.M. Phase; S.N. Kale (pp. 4808-4812).

We report on study of morphology, optical contrast and transport characteristics of La_0.7Ba_0.3MnO₃ (LBMO) manganite thin films bilayered with SnO₂ on Si (001) substrate, synthesized using pulsed laser deposition system. X-ray diffraction study reveals that both LBMO and SnO₂ show polycrystalline growth over the substrate. Atomic force microscopy shows interesting pyramidal structures of LBMO of size ∼2μm×1μm×0.1μm. On the other hand, SnO₂ grows in the form of close packed cylindrical clusters of ∼200nm radius. Near-field optical microscopy (NSOM) study using 532nm laser reveal that optical NSOM output intensity in LBMO is four times less than SnO₂ signal. Transport characterizations show that this bilayer configuration exhibit non-linear current–voltage characteristics from 300 upto 50K. The nature becomes linear below this temperature. The results project the system as a promising candidate in non-conventional device category in the area of spintronics.

Keywords: PACS; 71.20.−b; 73.21.Ac; 73.40.Qv; 74.25FyManganites; Semiconductors; Transport; Atomic force microscopy

Microstructural effects on the formation and degradation of zinc phosphate coatings on 2024-Al alloy by A.S. Akhtar; P.C. Wong; K.C. Wong; K.A.R. Mitchell (pp. 4813-4819).

The formation of zinc phosphate (ZPO) coatings on 2024-T3 aluminum alloy was studied using scanning electron microscopy (SEM), scanning Auger microscopy (SAM) and X-ray photoelectron spectroscopy (XPS), with an emphasis on microstructural effects involving second-phase particles and the alloy matrix. Surface polishing results in an Al–Cu–Mg particle surface that contains metallic Cu as well as an overlayer of aluminum and magnesium oxide, while larger amounts of aluminum oxide are present on the Al–Cu–Fe–Mn particle and matrix. When dipped in an acidic ZPO coating solution, the oxide covering the Al–Cu–Mg particle is etched most easily, and metallic Cu near the surface makes that region most cathodic, allowing more coating deposition compared with the other regions. The oxides on the Al–Cu–Fe–Mn and matrix regions are similar, thereby confirming that the observed differences in ZPO coating characteristics at these two regions arise from their underlying electrochemical characteristics. Immersion of a coated 2024-Al sample in corrosive NaCl solution for extended periods indicates that the ZPO provides better protection to the second-phase particles than to the matrix.

Keywords: PACS; 81.65.Kn; 82.80.PvZinc phosphating; Aluminum alloy; Microstructure; Surface oxide; Corrosion; Auger electron spectroscopy

Reflectivity modification of polymethylmethacrylate by silicon ion implantation by Georgi B. Hadjichristov; Victor Ivanov; Eric Faulques (pp. 4820-4827).

The effect of silicon ion implantation on the optical reflection of bulk polymethylmethacrylate (PMMA) was examined in the visible and near UV. A low-energy (30 and 50keV) Si⁺ beam at fluences in the range from 10¹³ to 10¹⁷cm⁻² was used for ion implantation of PMMA. The results show that a significant enhancement of the reflectivity from Si⁺-implanted PMMA occurs at appropriate implantation energy and fluence. The structural modifications of PMMA by the silicon ion implantation were characterized by means of photoluminescence and Raman spectroscopy. Formation of hydrogenated amorphous carbon (HAC) layer beneath the surface of the samples was established and the corresponding HAC domain size was estimated.

Keywords: PACS; 42.70.Jk; 61.41.+e; 61.82.Pv; 78.30.Jw; 78.40.Me; 78.55.Kz; 78.66.Qn; 78.68.+mIon implanted polymers; Optical properties; Reflectivity; Polymethylmethacrylate; PMMA

Oxidation mechanism of hydrogen-terminated Ge(100) surface by Kibyung Park; Younghwan Lee; Jonghyuck Lee; Sangwoo Lim (pp. 4828-4832).

Control of the surface chemistry to prepare a robust termination on the Ge surface is crucial for the development of high-end Ge devices. In this study, oxidation of a H-terminated Ge surface was studied in air ambient and H₂O using a multiple internal reflection Fourier transform infrared spectroscopy (MIR FT-IR) technique. Ge surface treated in less diluted HF exhibited a stronger Ge–H peak intensity, and the surface was easily oxidized in the air ambient. Therefore, it is believed that the treatment of the Ge surface in highly diluted HF solution has an advantage in suppressing the oxidation of Ge in the air ambient. For the oxidation of Ge(100) surface in air ambient, the Ge surface is attacked by oxidizing agents to break Ge–H and Ge–Ge bonds, and the transition GeO_x layer is first formed, followed by a layer-by-layer GeO₂ formation with the increase in exposure time. When the H-terminated Ge surface was treated in H₂O, GeO_x was mainly formed, the thickness of the oxide layer was not changed with an increase in treatment time, and the Ge surface was maintained in a suboxide state, which exhibits a different oxidation mechanism from that in air ambient.

Keywords: PACS; 33.20.Ea; 81.65.MqGermanium oxide; Layer-by-layer; Suboxide; FT-IR

The effect of chemical treatment on apatite-forming ability of the macroporous zirconia films formed by micro-arc oxidation by Yuanyuan Yan; Yong Han; Chunguo Lu (pp. 4833-4839).

Macroporous and nano-crystalline zirconia film was prepared by micro-arc oxidation (MAO) of zirconium, and the effect of chemical treatment in H₂SO₄ or NaOH aqueous solutions on the microstructure and apatite-forming ability of the film was investigated. Compared with the MAO film, the chemically treated films do not exhibit apparent changes in phase component, morphology and grain size, however, have more abundant basic Zr–OH groups. The films treated with H₂SO₄ and NaOH solutions can induce apatite formation on their surfaces in simulated body fluids (SBF) within 1 day, whereas no apatite was detected on the untreated ZrO₂ surface by 30 days. It is believed that the enhanced apatite-forming ability of the chemically treated ZrO₂ films is related to the abundant basic Zr–OH groups on their surface.

Keywords: PACS; 68.55.Jk; 68.55.Nq; 82.33.Xj; 87.68.+z; 82.45.Cc; 68.43.−hZirconia film; Micro-arc oxidation; Chemical treatment; Bioactivity

Local field-emission characteristic of individual AlN cone fabricated by focused ion-beam etching method by Y.L. Li; C.Y. Shi; J.J. Li; C.Z. Gu (pp. 4840-4844).

Highly (002)-oriented AlN film was deposited on n-type (100)-oriented silicon substrates by the radio frequency magnetron sputtering method. An individual AlN cone with high aspect ratio was fabricated by the focused ion-beam (FIB) etching process in the surface of an as-formed AlN film. This etching method can easily control the tip radius and height to obtain AlN cones with different aspect ratios. The field-emission property of the individual AlN cone was measured in a scanning electron microscopy system equipped with a movable probe as the anode above the AlN tip. The results indicated that the as-formed single AlN cone with high aspect ratio possessed good field-emission ability although it only had a tiny emission area. Compared with a single Si tip fabricated by the same method, a single AlN cone exhibits better field-emission ability, and hence, has great potential as a promising candidate of point electron source for application in vacuum electronic devices.

Keywords: PACS; 79.70+q; 81.16−cAlN cone; Field emission; Focused ion-beam etching

Study of photoexcited plasma in p-doped GaAs beveled structures by micro-Raman spectroscopy by R. Srnanek; G. Irmer; D. Donoval; I. Novotny; B. Sciana; D. Radziewicz; M. Tlaczala (pp. 4845-4855).

The generation and properties of photoexcited steady-state plasma of electrons and holes in bevel-shaped p-type GaAs structures were studied by micro-Raman spectroscopy. The best correspondence of theoretical calculations with experimental spectra was obtained by using of photoexcited carrier concentration of 1.1×10¹⁷cm⁻³ and mobility 600 and 40cm²/Vs for the photoexcited steady-state electrons and holes, respectively. The analysis of the plasma behavior and its coupling with longitudinal optical phonons at different positions along the bevel shows that the mode resulting from this coupling causes the changes of Raman intensities recorded in frequency positions of transversal (TO) and longitudinal (LO) optical phonon peaks. These changes were further studied and physical interpretation was provided. The dependence of their ratio in the region affected by surface depletion layer can be fitted by linear function very well. The linearity was observed at all studied structures. This behavior on beveled structures prepared by special treatment with very low bevel angle can be used for analysis of the p-type GaAs nanostructures, particularly for measurement and extraction of a doping profile of p-type impurities in GaAs with very high resolution in nm scale.

Keywords: PACS; 78.30.Fs; 68.55.Ln; 73.20.MfMicro-Raman; Zn-doped GaAs; Beveled structure; Photoexcited steady-state plasma; Plasmon-LO-phonon coupling; Doping profile

Removal of scratch on the surface of MgO single crystal substrate in chemical mechanical polishing process by R.K. Kang; K. Wang; J. Wang; D.M. Guo (pp. 4856-4863).

Etching and chemical mechanical polishing (CMP) experiments of the MgO single crystal substrate with an artificial scratch on its surface are respectively performed with the developed polishing slurry mainly containing 2vol.% phosphoric acid (H₃PO₄) and 10–20nm colloidal silica particles, through observing the variations of the scratch topography on the substrate surface in experiments process, the mechanism and effect of removing scratch during etching and polishing are studied, some evaluating indexes for effect of removing scratch are presented. Finally, chemical mechanical polishing experiments of the MgO substrates after lapped are conducted by using different kinds of polishing pads, and influences of the polishing pad hardness on removal of the scratches on the MgO substrate surface are discussed.

Keywords: MgO single crystal; Substrate; Scratch; Chemical mechanical polishing; Surface roughness

Influence of ZrO₂ in HfO₂ on reflectance of HfO₂/SiO₂ multilayer at 248nm prepared by electron-beam evaporation by Jingmei Yuan; Lei Yuan; Hongbo He; Kui Yi; Zhengxiu Fan; Jianda Shao (pp. 4864-4867).

Influence of ZrO₂ in HfO₂ on the reflectance of HfO₂/SiO₂ multilayer at 248nm was investigated. Two kinds of HfO₂ with different ZrO₂ content were chosen as high refractive index material and the same kind of SiO₂ as low refractive index material to prepare the mirrors by electron-beam evaporation. The impurities in two kinds of HfO₂ starting coating materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum (GDMS) technology and secondary ion mass spectrometry (SIMS) equipment, respectively. It showed that between the two kinds of HfO₂, either the bulk materials or their corresponding films, the difference of ZrO₂ was much larger than that of the other impurities such as Ti and Fe. It is the Zr element that affects the property of thin films. Both in theoretical and in experimental, the mirror prepared with the HfO₂ starting material containing more Zr content has a lower reflectance. Because the extinction coefficient of zirconia is relatively high in UV region, it can be treated as one kind of absorbing defects to influence the optical property of the mirrors.

Keywords: PACS; 68.65.Ac; 68.55.Ln; 78.66.−wHfO; ₂; /SiO; ₂; multilayer; ZrO; ₂; impurity; Reflectance

Water vapor adsorption onto activated carbons prepared from cattle manure compost (CMC) by Qingrong Qian; Satoshi Sunohara; Yuichi Kato; Muhammad Abbas Ahmad Zaini; Motoi Machida; Hideki Tatsumoto (pp. 4868-4874).

Activated carbons were prepared from cattle manure compost (CMC) using zinc chloride activation. The structural and surface chemical characteristics of CMC-based activated carbons were determined by N₂ adsorption–desorption and Boehm titration, respectively. The water vapor adsorption properties of the prepared activated carbons with various pore structure and surface nature were examined, and the mechanism of water adsorbed onto activated carbon was also discussed. The results show that the adsorption of water vapor on carbons begins at specific active sites at low relative humidity (RH), followed by micropore filling at medium RH through the formation of pentamer cluster of water molecules in the narrow micropores. The water vapor adsorption capacity of activated carbon is predominantly dependent on its pore volume and surface area. Although capillary condensation is not the mechanism for water adsorption onto activated carbon, water can adsorb on narrow mesopore to some extent.

Keywords: Cattle manure compost; Activated carbon; Water vapor adsorption; Humidity

Optical properties of single-phase β-FeSi₂ films fabricated by electron beam evaporation by Daoren Gong; Dongsheng Li; Zhizhong Yuan; Minghua Wang; Deren Yang (pp. 4875-4878).

Single-phase semiconducting iron disilicide (β-FeSi₂) films on silicon substrate were fabricated by electron beam evaporation (EBE) technique. For preventing the oxidation of Fe film, silicon/iron/silicon sandwich structure films with different thickness of silicon and iron were deposited and then annealed at different temperatures. X-ray diffraction (XRD), Raman and Fourier transform infrared spectroscopy (FTIR) measurements were carried out to study the phase distribution and crystal quality of the films. Single-phase β-FeSi₂ with high crystal quality was achieved after annealing at 800°C for 5h. An apparent direct bandgap E_g of approximately 0.85–0.88eV was observed in the β-FeSi₂ films. It is considered that the silicon/iron/silicon sandwich structure is suited for formation of single-phase β-FeSi₂ with high crystal quality.

Keywords: Electron beam evaporation (EBE); Sandwich structure films; Single-phase β-FeSi; ₂; Optical absorption

Nd- or Zr-modified CuO–CeO₂/Al₂O₃/FeCrAl monolithic catalysts for preferential oxidation of carbon monoxide in hydrogen-rich gases by S.H. Zeng; Y. Liu (pp. 4879-4885).

This work presents a study on the role of the additives over CuO–CeO₂/Al₂O₃/FeCrAl monolithic catalysts for the preferential oxidation of CO. The monolithic catalysts were prepared by in situ combustion method and characterized using SEM, XRD and TPR techniques. The results show that the addition of neodymium or zirconium in the CuO–CeO₂/Al₂O₃/FeCrAl catalysts influences the dispersion state of copper oxide and ceria, lowers the activity of hydrogen oxidation and broadens the temperature window for total CO-conversion.

Keywords: Ceria; Copper oxide; Preferential oxidation; Neodymium; Zirconium; Monolith; FeCrAl

Oxygen flux influence on the morphological, structural and optical properties of Zn1−_xMg_xO thin films grown by plasma-assisted molecular beam epitaxy by S.C. Su; Y.M. Lu; Z.Z. Zhang; B.H. Li; D.Z. Shen; B. Yao; J.Y. Zhang; D.X. Zhao; X.W. Fan (pp. 4886-4890).

The Zn1−_xMg_xO thin films were grown on Al₂O₃ substrate with various O₂ flow rates by plasma-assisted molecular beam epitaxy (P-MBE). The growth conditions were optimized by the characterizations of morphology, structural and optical properties. The Mg content of the Zn1−_xMg_xO thin film increases monotonously with decreasing the oxygen flux. X-ray diffractometer (XRD) measurements show that all the thin films are preferred (002) orientated. By transmittance and absorption measurements, it was found that the band gap of the film decreases gradually with increasing oxygen flow rate. The surface morphology dependent on the oxygen flow rate was also studied by field emission scanning electron microscopy (FE-SEM). The surface roughness became significant with increasing oxygen flow rate, and the nanostructures were formed at the larger flow rate. The relationship between the morphology and the oxygen flow rate of Zn1−_xMg_xO films was discussed.

Keywords: Zn; 1−; _x; Mg; _x; O; P-MBE; Zn/Mg

Optical and AFM study of electrostatically assembled films of CdS and ZnS colloid nanoparticles by Suryajaya; A. Nabok; F. Davis; A. Hassan; S.P.J. Higson; J. Evans-Freeman (pp. 4891-4898).

CdS and ZnS semiconducting colloid nanoparticles coated with the organic shell, containing either SO₃⁻ or NH₂⁺ groups, were prepared using the aqueous phase synthesis. The multilayer films of CdS (or ZnS) were deposited onto glass, quartz and silicon substrates using the technique of electrostatic self-assembly. The films produced were characterized with UV–vis spectroscopy, spectroscopic ellipsometry and atomic force microscopy. A substantial blue shift of the main absorption band with respect to the bulk materials was found for both CdS and ZnS films. The Efros equation in the effective mass approximation (EMA) theoretical model allowed the evaluation of the nanoparticle radius of 1.8nm, which corresponds well to the ellipsometry results. AFM shows the formation of larger aggregates of nanoparticles on solid surfaces.

Keywords: PACS; 73.61.Ga; 78.20.Ci; 78.67.HcColloid nanoparticles; Electrostatic self-assembly; Quantum confinement; Ellipsometry

Preparation and surface modification of silicon nanowires under normal conditions by LiJuan Wan; WenLi Gong; Kewei Jiang; HuiLin Li; BaiRui Tao; Jian Zhang (pp. 4899-4907).

Preparation and surface modification of silicon nanowires (SiNWs) grown by the metal catalyzed solution method under normal conditions (room temperature, 1atm) had been studied in this paper. Firstly, SiNWs using a simple solution method via electroless metal deposition (EMD) of silver under room temperature, standard pressure had been prepared. The influence of the growth parameters such as solution concentration, etching time on the SiNWs formation had been studied. Secondly, the surface modification of SiNWs with platinum and copper had been investigated. The results indicated that the SiNWs modified with Pt and Cu showed different surface morphologies. Pt modification on SiNWs presented in the form of nanoparticles, whereas Cu modification in the form of membrane. Therefore, the Pt modified SiNWs have more vast surface-to-bulk ratio than the unmodified ones, and SiNWs modified with copper nanoparticles will lead to the smaller surface-to-bulk ratio. So the platinum-modified SiNWs have a promising application in sensors’ field.

Keywords: SiNWs; Normal condition; Electroless metal deposition; Metal surface modification

Work function engineering and its applications in ohmic contact fabrication to II–VI semiconductors by B. Ghosh (pp. 4908-4911).

CdTe and the associated materials are suffering from ohmic contacting problem due to their high electron affinity and consequently large function. Ni, Au, Pt and Pd have large work function and have possibility to match with CdTe. However, except Ni other materials have problems in large-scale applications. In the present paper possibility of Ni has been explored through work function engineering. Work function and bulk resistivity of Ni has been modulated with other materials like, Cu, Au, Mo, W and Co. A theoretical model has been developed to calculate the effective work function and bulk resistivity after modulation. Modulated materials have been deposited over thin film CdTe using electroless technique to evaluate the validity between the theoretical and experimental results. Results indicated about good matching between them. To the best of knowledge this is the first time applications on such type of methodology has presented in contact applications to CdTe.

Keywords: Work function; Ohmic contact; Electroless technique; CdTe

Chromium-doped titanium dioxide thin-film photoanodes in visible-light-induced water cleavage by Chien-Cheng Tsai; Hsisheng Teng (pp. 4912-4918).

A new method for the synthesis of nanocrystalline anatase Cr-doped TiO₂ colloids from nanotubes utilizing the hydrothermal ion-intercalation (HII) method has been devised using hydrothermal treatment in an acidic environment. To investigate the photoelectrochemical reaction that occurs when water is split into H₂ and O₂ under visible light, a Cr-doped TiO₂ thin film served as a model photoelectrode. The photoelectrochemical activity of Cr-doped TiO₂ was higher than that of the undoped sample. The photoelectrochemical activity of photoelectrodes increased drastically with increased chromium doping. A red shift in the band gap was induced by Cr doping of TiO₂. It was revealed that the Cr-doped TiO₂ photoelectrode was able to utilize a wide range of light in the visible region of the spectrum. At high Cr concentrations, the lower photoelectrochemical activity is attributed to the effect of Cr³⁺ ion recombination and excess Cr³⁺ ions forming secondary phase Cr₂O₃.

Keywords: Titanate nanotube; Photoelectrode; Water splitting; Visible light; Chromium-doped; Thin film

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Applied Surface Science (v.254, #15)

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Applied Surface Science (v.254, #15)