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Applied Surface Science (v.245, #1-4)

Author Index (pp. i-iv).

Subject Index (pp. v-xix).

A combinatorial analysis of deposition parameters and substrates on performance of μc-Si:H thin films by VHF-PECVD by Xiao-dan Zhang; Ying Zhao; Feng Zhu; Chang-chun Wei; Chun-ya Wu; Yan-tao Gao; Jian Sun; Guo-fu Hou; Xin-hua Geng; Shao-zhen Xiong (pp. 1-5).

Influence of silane concentration (SC), substrate temperature (Ts) and substrates on the properties of materials deposited by very high frequency plasma enhanced chemical vapor deposition was studied. SC and Ts had a great impact on the structure of materials, especially changed from amorphous to microcrystalline silicon. The results of FTIR (flourier transform infrared) showed that material fabricated at higher temperature appeared a little oxygen peak located at 1017cm⁻¹, which means that oxygen easily entered into the materials at higher Ts. However, microcrystalline silicon thin film prepared at low Ts easily adsorbed oxygen characterized with oxygen content increased largely with the prolong of time. The results of Raman evidently showed that crystalline volume fraction (Xc) also depended on the type and texture of substrate. Higher texture means higher volume crystalline fraction for the same type of substrate.

Keywords: PACS; 61.82.Fk; 87.64.JeMicrocrystalline silicon; Substrates; FTIR

Correlation between the growth-per-cycle and the surface hydroxyl group concentration in the atomic layer deposition of aluminum oxide from trimethylaluminum and water by Riikka L. Puurunen (pp. 6-10).

The growth-per-cycle (GPC) in the trimethylaluminum/water atomic layer deposition (ALD) process is shown to be quantitatively correlated with the surface OH group concentration before the trimethylaluminum reaction. The correlation corresponds to a reaction chemistry, where several types of gas–solid reactions (ligand exchange, dissociation/association) can occur simultaneously, and where steric hindrance by adsorbed methyl groups terminates the trimethylaluminum reaction. The commonly assumed reaction chemistry where one OH group bonds one aluminum atom through ligand exchange does not describe satisfactorily the trimethylaluminum/water process, and should perhaps not be expected to describe other ALD processes either.

Keywords: PACS; 81.15.Aa; 81.15.Gh; 82.33.YaAtomic layer deposition; Mechanism; Aluminum oxide; High-; κ; dielectrics

The study on the interface adhesion comparison of the MgF₂, Al₂O₃, SiO₂ and Ag thin films by Xueke Xu; Zhaosheng Tang; Jianda Shao; Zhengxiu Fan (pp. 11-15).

Adhesion between the interface of pure silver thin film and three kinds of low refractive index coatings MgF₂, Al₂O₃, SiO₂ were compared in this article. The results indicated that the adhesion of Al₂O₃ and Ag was evidently superior to that of MgF₂ and Ag, and the adhesion of MgF₂ and Ag was evidently superior to that of SiO₂ and Ag. Reasons were analyzed accordingly. On the other hand, we compared the effect on the optical characteristic of Ag film when these three kinds of films were used as protective coatings and enhanced coatings. Considering the difference of the adhesion between Ag and MgF₂, Al₂O₃, SiO₂, suited uses are given for each other.

Keywords: Ag films; Adhesion; Optical performance

Surface modification of polymer nanofibres by plasma treatment by Q.F. Wei; W.D. Gao; D.Y. Hou; X.Q. Wang (pp. 16-20).

Polymer nanofibres have great potential for technical applications in biomaterials, filtration, composites and electronics. The surface properties of nanofibres are of importance in these applications. In this study, cold gas plasma treatment was used to modify the surface of polyamide 6 nanofibres prepared by electrospinning. The chemical nature of the nanofibre surfaces was examined by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was employed to study the surface characteristics of the fibres. The AFM results indicate a significant change in the morphology of the fibre surface before and after plasma treatment. A Philips Environmental Scanning Electron Microscopy (ESEM) was also used to study the wetting behaviour of the fibres. In the ESEM, relative humidity was raised to 100% to facilitate the water condensation onto fibre surfaces for wetting observation. The ESEM observation revealed that the plasma treatment significantly altered the surface wettability of the polyamide 6 nanofibres

Keywords: PACS; 52.77.Bn; 81.65.Cf; 87.64.EeNanofibres; Plasma treatment; XPS; AFM; Wetting; ESEM

Study on the mechanism of self-organized carbon nanotips without catalyst by plasma-enhanced hot filament chemical vapor deposition by B.B. Wang; Soonil Lee; H. Yan; C.Z. Gu; B. Wang (pp. 21-25).

Carbon nanotips were grown on a silicon substrate without catalyst by plasma-enhanced hot filament chemical vapor deposition using a mixture of methane, ammonia and hydrogen as the reaction gases. Due to production of plasma during growing the carbon nanotips, the reaction gases were ionized into various kinds of ions and these ions played different roles in the process of growing the carbon nanotips. Based on different effects of the ions and combined with theory related to plasma, a model of the self-organized carbon nanotips without catalyst was put forward.

Keywords: PACS; 52.77.Bn; 81.07.Bc; 81.15.GhPlasma; Carbon nanotips; Chemical vapor deposition

Surface confined self-assembled fullerene nanoclusters: a microscopic study by Rashmi R. Sahoo; Archita Patnaik (pp. 26-38).

The structure of the C₆₀-fullerene terminated aminothiol self-assembled monolayers (SAM) generated by tethering the fullerene molecules to the surface of 11-amino-1-undecane thiol (11-AUT) SAM on gold surface was investigated by dynamic contact angle measurements, Fourier transform infrared reflection–absorption spectroscopy (FTIR-RAS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). A two-step procedure was followed consisting of the chemisorption of the amine-terminated organosulfur compound on oriented gold, followed by its reaction at the solid liquid interface with C₆₀ fullerenes. Covalent binding of fullerenes to these attachment layers was accessed by the above experimental techniques. IR-RAS showed several major features in the C₆₀ skeleton ring vibration region along with all the characteristic features of the amino thiol. With increase in carbon to sulfur ratio, appearance of C 1s shake-up satellite peak due to characteristic π–π^* transition of the C₆₀ backbone confirmed theNH₂ binding at the 6,6 double bond of the C₆₀ cage. Atomic force microscopy showed smooth, homogeneous areas of the monomolecular films, covered by regular small microcrystalline grains on the fullerene-terminated monolayer surface. Possible explanations for these experimental findings are discussed.

Keywords: C; ₆₀; fullerene; Self-assembled monolayers; Amino thiol; FTIR-RAS; X-ray photoelectron spectroscopy; Atomic force microscopy

Positive magnetoresistance of Co–Cu film prepared by ion beam assisted deposition by F. Zeng; Q.W. Gen; Y. Gao; F. Pan (pp. 39-44).

The Co–Cu alloy films were prepared using IBAD at various ion incidence angles. The compositions of all films did not vary significantly with the ion incidence angle. The sample prepared under perpendicular ion bombardment was fcc structure with composition of Co₈₃Cu₁₇ and lattice constant of 3.57Å. It was easily magnetized in the film plane. Magnetoresistance was performed on all samples at room temperature. The MR ratio was found only in the sample with perpendicular ion incidence. The measured MR ratio is positive and consistent with the magnetization variation under the external field. The full width at half maximum (FWHW) of the MR is narrow about 10–15Oe. Considering the effect of ion bombardment, we regarded that the interface between the alloy film and the substrate contributed to the positive MR (PMR). There was another conductive mechanism switched in this interface.

Keywords: PACS; 73.43.Qt; 75.70.Cn; 75.47.−mPositive magnetoresistance; Co–Cu alloy; Ion beam assisted deposition

Effect of dc negative-bias and silicon introduction on performance of Si–B–N composite film by RF-PECD technique by Meng Hua; Yu Xiang; Yu Junfeng; Wang Chengbiao (pp. 45-50).

Under action of different dc negative-bias voltages on samples incorporating with silicon, a series of Si–B–N composite films were synthesized on steel 1045 using RF-PECVD technique (radio-frequency plasma enhanced chemical vapor deposition), and the surface analysis of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and etc. were followed. The experimental results showed: Si–B–N composite films had an obvious mixture phase of c-BN and h-BN crystal at a certain dc negative bias, and the film's mechanical performances including micro-hardness and adhesion were improved. Moreover, bias effect on deposition performance of Si–B–N composite film has been systematically investigated, and silicon introduction was found to be necessary for the growth of Si–B–N film and the improvement of adhesion.

Keywords: Si–B–N composite film; dc negative-bias; Silicon introduction; c-BN formation

Non-isothermal preform infiltration during the vacuum-assisted resin transfer molding (VARTM) process by M. Grujicic; K.M. Chittajallu; Shawn Walsh (pp. 51-64).

A control-volume finite-element model is developed to analyze the infiltration of a fiber preform with resin under non-isothermal conditions within a high-permeability resin-distribution medium based vacuum-assisted resin transfer molding (VARTM) process. Due to the exposure to high temperatures during preform infiltration, the resin first undergoes thermal-thinning which decreases its viscosity. Subsequently however, the resin begins to gel and its viscosity increases as the degree of polymerization increases. Therefore, the analysis of preform infiltration with the resin entails the simultaneous solution of a continuity equation, an energy conservation equation and an evolution equation for the degree of polymerization. The model is applied to simulate the infiltration of a rectangular carbon fiber based preform with the NBV-800 epoxy resin and to optimize the VARTM process with respect to minimizing the preform infiltration time. The results obtained suggest that by proper selection of the ramp/hold thermal history of the tool plate, one can reduce the preform infiltration time relative to the room-temperature infiltration time. This infiltration time reduction is the result of the thermal-thinning induced decrease in viscosity of the ungelled resin.

Keywords: PACS; 61.41.+e (Polymers)Vacuum-assisted resin transfer molding (VARTM) process; Modeling and simulations

Characterization and catalytic activity of Cu–Co spinel thin films catalysts by P. Stefanov; I. Avramova; D. Stoichev; N. Radic; B. Grbic; Ts. Marinova (pp. 65-72).

The Cu–Co mixed oxide catalysts were prepared on a La₂O₃/ZrO₂/SS support by thermal decomposition of nitrate precursors. The catalyst samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectrum (XPS) and Brunauer–Emmet–Teller (BET) surface area. The XPS data indicated the formation of some amount of CuO together with the Cu–Co spinel after annealing at 550°C. The Cu–Co/ZrO₂/SS thin film catalysts were tested for three-way catalytic performance and showed moderate activity.

Keywords: PACS; 81.15.P; 82.65.Jv; 82.80.PvCu–Co oxide; Lanthana/zirconia thin film; Catalyst; XPS

Deposition of indium nitride films by activated reactive evaporation process – a feasibility study by Sheetal J. Patil; Dhananjay S. Bodas; A.B. Mandale; S.A. Gangal (pp. 73-78).

Indium nitride (InN) films are deposited by ‘activated reactive evaporation (ARE)’ process using parallel plate coupled nitrogen plasma (radio frequency source of 13.56MHz) and evaporation of pure indium powder by resistive heating. Depositions are carried out by varying RF plasma power, on n-type silicon 〈100〉 substrate, maintained at room temperature, at a nitrogen gas pressure of 1.06×10⁻¹Pa (8×10⁻⁴Torr). The film's crystallinity was examined by X-ray diffraction (XRD) and topography by scanning electron microscope (SEM). The diffraction pattern shows polycrystalline nature of the deposited films with characteristics of hexagonal structure. XRD peak intensity increases with increase in power. SEM observations show a smooth and pinhole free surface having improved quality of film with hexagonal structure as the power is increased from 60 to 120W. Primary X-ray photoelectron spectroscopy (XPS) results show binding energies of the In 3d levels and N 1s level matching well with that of stoichiometric InN. Further, the refractive index of the films, measured by ellipsometry, is in the range of η=2.79–2.91 with the variation of plasma power, which is in good agreement with the standard value for indium nitride ( η=2.9). These results indicate the feasibility of using, ‘activated reactive evaporation (ARE)’ process for indium nitride depositions on silicon 〈100〉 substrates maintained at room temperature.

Keywords: PACS; 68.55.−a; 68.60.−p; 71.55.Eq; 82.80.PvIndium nitride; Activated reactive evaporation; XRD; SEM; Ellipsometry

Interdiffusion coefficients of various cobalt base alloy coatings for Cu/Au system by C.L. Siu; H.C. Man; C.H. Yeung (pp. 79-86).

The interdiffusion coefficients of electrodeposited Co–Mo, Co–P, Co–Mo–P with Cu substrate were studied at temperature ranging from 400 to 800°C, by micro-profiling method using energy dispersive X-ray spectroscopy (EDS). Chemical interdiffusion coefficients were derived using the Boltzmann–Matano method. At 400–500°C, the interdiffusion coefficients for Cu/Co–P couples have the same order of magnitude as the Cu/Co–Mo couples. It was found that the interdiffusion coefficients for nickel are higher than that of the cobalt base alloys. The Co–Mo coating becomes poor in term of barrier property when the temperature is above 700°C.

Keywords: Electroplating; Amorphous coating; Barrier coating; Interdiffusion coefficients; Nickel ion release

XPS, TDS and static SIMS studies of binary Pd/Al system properties: correlation between Pd–Al bimetallic interaction and CO adsorption by Iva Matolínová; Viktor Johánek; Tomáš Skála; Kateřina Veltruská; Vladimír Matolín (pp. 87-93).

Carbon monoxide (CO) adsorption properties of Pd/Al systems have been studied using X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS) and static secondary ion mass spectroscopy (SSIMS) under UHV conditions. Measured XPS and TDS spectra were compared to that of clean bulk metals (Pd, Al).Pd adlayers, prepared by vacuum evaporation onto a pure polycrystalline Al surface, exhibited a strong interaction with Al atoms resulting in formation of a Pd–Al alloy of a noble metal-like electronic structure. The shifts of the Pd 3d core levels and the Pd 4d-band centroid toward higher binding energies due to bimetallic bond formation were observed. The CO TDS spectra consisted of two desorption peaks, both lying lower than the one typical for a Pd foil, indicating distinct weakening of the Pd–CO chemisorption bond. Partial CO dissociation on the Pd/Al surface during adsorption/desorption cycles, accompanied by CO₂ and H₂O production, was observed. CO dissociation caused creation of Pd–C and Al–O chemical bonds on the Pd/Al surface resulted in weakening of the Pd–Al bimetallic bond.

Keywords: PACS; 82.80.Pv; 82.80.Ms; 82.65.Jv; 81.05.BxX-ray photoelectron spectroscopy; Thermal desorption spectroscopy; Secondary ion mass spectroscopy; Catalysis; Aluminum; Palladium; Alloys; Carbon monoxide

Growth of SnO₂ thin films on self-assembled layers of the short-chain alkoxysilane by Jin-Li Zhang; Wei Li; Yi Zhai; Hong Yang; Yi-Ping Wang (pp. 94-101).

The growth behavior and structure of self-assembled layers of short-chain alkoxysilane of 3-mercaptopropyltrimethoxysilane (MPS) on hydroxyl-terminated substrates were investigated using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. It was indicated that the self-assembled layers of MPS formed island structures and deposited integrally on the substrates. Further, the deposition of SnO₂ thin films on the MPS-coated substrates was studied using X-ray diffraction (XRD), AFM, XPS, and the high-resolution stylus profilometers. It was proved that uniform and compact SnO₂ thin films indeed formed on the self-assembled layers of short-chain MPS. The as-deposited SnO₂ films were cassiterite and showed the property of semiconductors, which would have wide applications in gas sensors, solar cells, catalysts, etc.

Keywords: Self-assemble; Alkoxysilane; Thin films; SnO; ₂

Evolution of silicon surface microstructures by picosecond and femtosecond laser irradiations by Jingtao Zhu; Gang Yin; Ming Zhao; Deying Chen; Li Zhao (pp. 102-108).

We report the evolution of sharp conical spike array formed on the silicon surface under the cumulative picosecond (ps) and femtosecond (fs) laser pulse irradiations in SF₆ ambient. The experimental results suggest that the physical mechanisms of conical spike evolutions under ps and fs laser irradiations are different. Under the ps laser irradiation, silicon surface is melted before the spike arrays formed, while under the fs laser irradiation, the formation of spike arrays does not pass through the liquid phase. The evolution of microstructure is strongly dependent on the laser duration.

Keywords: PACS; 68.35.Bs; 61.82.Fk; 61.80.BaLaser material processing; Surface modification of solid; Laser ablation; Microstructuring; Femtosecond pulse; Picosecond pulse

Dependence of properties of N–Al codoped p-type ZnO thin films on growth temperature by J.G. Lu; L.P. Zhu; Z.Z. Ye; F. Zhuge; Y.J. Zeng; B.H. Zhao; D.W. Ma (pp. 109-113).

N–Al codoped p-type ZnO thin films have been realized by dc reactive magnetron sputtering in N₂O ambient. Hall measurement, X-ray photoelectron spectroscopy, X-ray diffraction and optical transmission were carried out to investigate the effect of growth temperature on the properties of codoped films. Results indicated that N–Al codoped p-type ZnO films with good structural, electrical and optical properties can only be obtained at an intermediate temperature region (e.g., 500°C). The codoped p-type ZnO had the lowest resistivity of 57.3Ωcm, and a carrier concentration up to 2.52×10¹⁷cm⁻³. In addition, the N–Al codoped p-type ZnO film deposited at 500°C was of good crystallinity with a (002) preferential orientation, and high transmittance about 90% in the visible region.

Keywords: PACS; 61.72.V; 72.80.E; 73.61.G; 78.66.HZnO thin films; N–Al codoping method; p-Type conduction; dc reactive magnetron sputtering

Reactive electron beam evaporated gadolinia films at ambient substrate temperature: optical properties and morphology studies by M. Senthilkumar; N.K. Sahoo; S. Thakur; R.B. Tokas (pp. 114-127).

Depositing optical coatings at ambient substrate temperature has been stimulating interest as it has a range of potential applications. However, developing such optical coatings especially using refractory oxides is challenging since they yield stable thin films mostly at elevated substrate temperatures. Gadolinia films (Gd₂O₃), in the present experiment, however, observed to form stable films even at ambient substrate temperatures when deposited through reactive electron beam deposition. In addition, the films exhibited interesting optical properties such as reasonably high refractive index and wide band gap, which are rarely obtainable with conventional oxide materials. During the deposition, rate and oxygen pressure have been systematically varied. The deposited films have subsequently been characterized for optical and band gap related properties using spectrophotometric as well as ellipsometric spectral measurements. Atomic force microscopy has also been employed to study the surface topography and morphological changes under various deposition conditions. Both oxygen pressure and rate of evaporation have observed to greatly influence both the optical constant and surface topography of the gadolinia films.

Keywords: PACS; 42.79.W; 78.66; 81.15.E; 61.16.CGadolinia films; Deep UV optical coatings; Optical properties; Rare earth oxides; Optical constants

Relationship between the C KVV Auger line shape and layered structure of graphite by A.P. Dementjev; K.I. Maslakov; A.V. Naumkin (pp. 128-134).

C KVV Auger electron spectra of highly oriented pyrolytic graphite (HOPG) (at different emission angles) and of quaterphenyl, fullerenes C60, single- and multi-wall carbon nanotubes (MWNT) have been studied. The interpretation of HOPG spectra is based on the angular dependence of the Auger line shape and on the comparison with the related carbon compounds. The Auger spectra of HOPG at normal ( S_HOPGn) and grazing ( S_HOPGg) emission are quite different at the high-energy side. We interpret the difference between the two spectra in terms of different sampling depth and interlayer interaction. The normal emission spectrum is formed by the top, underlying layers and interlayer interaction. The last is the interaction between π-electrons of the first and second layers. This π-state is closer to the Fermi level than the π-state of the single layer and may be responsible for metallic conductivity. Information on this π-state found in these experiments provides a unique method for identification of the interaction between carbon atomic layers or for differentiating between the single and double layer structures of carbon atoms.

Keywords: PACS; 79.20; 73.30.+y,73.25.+i; 73.20.−rGraphite; Auger spectroscopy; Surface sensitivity; Interlayer interaction

Dispersive surface properties of glass-ionomer cements determined by inverse gas chromatography by E. Andrzejewska; A. Voelkel; M. Andrzejewski; H. Limanowska-Shaw (pp. 135-140).

The surface properties of several glass-ionomer cements (GIC), restorative dental materials, (GC-Fuji, Chemadent G-J, Ketac Fil and Ketac Molar) were investigated for the first time by means of inverse gas chromatography. This method enables characterization of surface activity in dispersive (non-polar) and acid–base interactions. The ability of the surface of glass-ionomers to participate in dispersive interactions was expressed by the use of the dispersive component of surface free energyγsd. This parameter was determined with satisfactory precision, meaning that the values ofγsd can be further used in the discussion of the influence of the type of GIC, its preparation and the storage time on the surface properties. The greatest capacity for dispersive interactions was revealed by Ketac Molar and the lowest by GC-Fuji. Dispersive interactions in the surface activity of glass-ionomers increased with increasing storage time after cement preparation.

Keywords: PACS; 68.10.Cr; 68.10.Gw; 82.65.DpGlass-ionomers; Surface activity; Inverse gas chromatography; Dispersive interactions

Effect of Au overlayer on PtSi ohmic contacts with n-InP by W.C. Huang (pp. 141-148).

This investigation considers ohmic contact structures Si/Pt/n-InP and Au/Si/Pt/n-InP. The processing conditions achieving low specific contact resistance were derived. Experimental results indicated that the Si/Pt/n-InP showed poor ohmicity; while a low specific contact resistance of 3.32×10⁻⁵Ωcm² was obtained on the Au/Si/Pt/n-InP contact after rapid thermal annealing (RTA) at 550°C for 30s. Additionally, the Si/Pt/n-InP contact underwent a sintering reaction. The Au/Si/Pt/n-InP was formed in an alloying reaction and the contact morphology was a little rough after thermal annealing. The ohmicity of the Au/Si/Pt/n-InP contact was attributed to Si doping, and determined by the alloyed reaction and the decomposition of the epitaxial layer of the metallization/InP interface. The Au/Si/Pt/n-InP also exhibited good thermal stability without degradation, with a low maintained specific contact resistance of 2.77×10⁻⁵Ωcm² after 400°C for 80h of thermal aging.

Keywords: Ohmic contact; Pt; InP; Specific contact resistance

Acid–base surface properties of glass-ionomers determined by IGC by A. Voelkel; E. Andrzejewska; H. Limanowska-Shaw; M. Andrzejewski (pp. 149-154).

The surface properties of several glass-ionomer restorative dental materials (GC Fuji, Chemadent G-J, Ketac Fil and Ketac Molar) were investigated by means of inverse gas chromatography. The capacity of the surface of glass-ionomers to undergo specific interactions was expressed using the specific component of free energy Δ G^s as well as the parameters K_A and K_D to describe the ability of the cement to act both as an electron acceptor and an electron donor, respectively. The character of the examined surface was expressed with the use of the S_C parameter. All these parameters were determined with a high degree of precision. It was found that the surface of glass-ionomer cements had a well-marked acidic character. The ability of the cement surface to take part in specific interactions differed with the various types of commercial products. The surface activity of the glass-ionomers investigated changed with the storage time (up to 6 months) indicating an on-going setting reaction.

Keywords: PACS; 68.10Cr; 68.10Gw; 82.65DpGlass-ionomers; Surface activity; Inverse gas chromatography; Acid–base interactions

CO₂ laser direct writing of silver lines on epoxy resin from solid film by J.G. Liu; C.H. Chen; J.S. Zheng; J.Y. Huang (pp. 155-161).

A technique of CO₂ laser direct writing from solid film was proposed in this paper. Patterns of silver lines were locally deposited on the non-conductive substrate using a preset layer of silver compound solid film, which was irradiated by focused CO₂ laser beam. The deposits were analyzed by XPS and EPMA. Results showed that metallic silver was dominant with an even distribution on the surface of the substrate, and part of the deposited silver had diffused into the substrate interior. The deposits had catalytic activity for the further electroless copper plating and had strong adhesion to the substrate. At last, the deposition mechanism and the dependence of the width of silver lines on the laser power and scan speed were roughly explored.

Keywords: PACS; 61.80.BCO; ₂; laser; Laser direct writing; Epoxy resin substrate; XPS and EPMA

Influence of the oxidative/reductive treatments on the activity of Pt/Ce_0.67Zr_0.33O₂ catalyst by Jun Fan; Xiaodong Wu; Rui Ran; Duan Weng (pp. 162-171).

A Pt/Ce_0.67Zr_0.33O₂ powder catalyst was prepared by sol–gel method. The as-received sample was successively oxidized, reduced and re-oxidized. The samples were characterized by XRD, XPS, TPR and three-way catalytic activity evaluation. The results supported the re-organization of the support and the occurrence of a strong metal–support interaction (SMSI) effect between platinum and ceria–zirconia mixed oxides. The oxidative/reductive atmosphere affected the structure and performance of the catalyst by the SMSI. It was suggested that a migration of Ce⁴⁺ from the bulk to the surface of the support took place during the reductive treatment, resulting in a formation of ceria-rich phase on the surface. The diffusion process was reversed when the atmosphere was switched to an oxidative one. The status of decoration or encapsulation of Pt by ceria-rich phase changed with the atmosphere, and hereby affected the activity of the catalyst. At temperatures below 300°C, the re-oxidized sample exhibited the best activity while the reduced one behaved the worst on the conversion of NO and CO, and the as-received one showed the worst on the oxidation of HC. After then the activity of the four samples tends to be the similar. The surface and interfacial Pt⁰ sites were both considered as the effective factors. Models were constructed to describe the diffusion of ions and oxygen vacancies as well as the possible surface structure serving as the carrier of Pt⁰ site which impacted on the catalytic activity remarkably.

Keywords: Pt; CeO; ₂; –ZrO; ₂; mixed oxides; Three-way catalysts; Redox treatment; Diffusion

Nitrogen ion implanted nanostructured titania films used in dye-sensitised solar cells and photocatalyst by Tuquabo Tesfamichael; Geoffrey Will; John Bell (pp. 172-178).

Nanostructured titania films were implanted with N at energies between 10 and 40keV and ion dose range 10¹⁴ to 5×10¹⁶cm⁻² and the films were characterized using various techniques. The surface morphology of the nanostructured films has been modified with ion implantation as observed using scanning electron microscopy (SEM). From SIMS depth profile analysis the amount of nitrogen was found to increase with increasing ion energy. The profile of N appeared to have a skewed Gaussian curve and the results have been explained using SRIM theoretical simulations. A maximum nitrogen concentration of about 6.08at% has been quantified by X-ray photoelectron spectrometer (XPS). Transmittance of the films decreases with increasing implantation energy and ion dose due to defects created by the ion implantation. Annealing can remove defects and thereby increase the transmittance of the films.

Keywords: PACS; 81.05.Rm; 82.65.−I; 78.20; 84.60.JNanocrystalline titania; N ion implantation; Surface morphology; Optical properties; N depth profiling

Effect of nickel-rich barrier layer on improvement of hot-dip zinc coating by S.M.A. Shibli; R. Manu; V.S. Dilimon (pp. 179-185).

Performances of hot-dip galvanized coatings not only depend on composition of the bath or the coating but significantly on the structure too. Nickel has been reported to have significant role in the improvement of the process but there is lack of sufficient reported detailed evidences. As it has already been reported that a nickel-rich barrier layer is formed during galvanization, and that the layer efficiently suppresses pitting, the present study focuses on investigating the role of nickel on the performance of hot-dip zinc coating. The structural influence due to the presence of nickel in galvanized substrates is discussed in this paper. Influence of nickel-rich barrier layer is identified as the cause for substantial improvement of the coating performance. Nickel content in the galvanic coating was analyzed layer-by-layer. Different techniques like OCP measurement and anodic polarizations were adopted to investigate and study the correlation between the structural change and the galvanic performance of the coating. The formation of nickel-rich barrier inner layer has a key role in improving the galvanic performance of the coating.

Keywords: Hot-dip zinc coating; Zn–Ni alloy; Galvanized coupons; Nickel-rich barrier

Deposition of plasma-polymerized hydroxyethyl methacrylate (HEMA) on silicon in presence of argon plasma by Dhananjay S. Bodas; Shrojal M. Desai; S.A. Gangal (pp. 186-190).

2-hydroxyethyl methacrylate (HEMA) has been deposited onto the surface of silicon substrate (thickness=500μm) using plasma polymerization technique. Polymerization process was carried out in an in-house developed inductively coupled plasma polymerization setup. The depositions were carried out using RF power supply (13.56MHz) at power of 75W for 10 and 40min. The RF supply was coupled to the inductance through a matching network. The effect of plasma polymerization (surface grafting) on the degree of surface modification has been investigated. The chemical changes on the polymer backbone are followed from the results of Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS), which show the peaks corresponding to the functional groups of the HEMA polymerized onto the silicon surface. The morphology of the modified surfaces has also been investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The hydrophilicity was determined from the water contact angle measurements.

Keywords: Plasma polymerization; Silicon; HEMA; XPS; SEMPACS; 52.75.Rx; 68.55.-a; 82.80.Pv; 61.16.B; 87.64.Dz

Laser-evoked coloration in polymers by H.Y. Zheng; David Rosseinsky; G.C. Lim (pp. 191-195).

Laser-evoked coloration in polymers has long been a major aim of polymer technology for potential applications in product surface decoration, marking personalised images and logos. However, the coloration results reported so far were mostly attributed to laser-induced thermal–chemical reactions. The laser-irradiated areas are characterized with grooves due to material removal. Furthermore, only single color was laser-induced in any given polymer matrix. To induce multiple colors in a given polymer matrix with no apparent surface material removal is most desirable and challenging and may be achieved through laser-induced photo-chemical reactions. However, little public information is available at present.We report that two colors of red and green have been produced on an initially transparent CPV/PVA samples through UV laser-induced photo-chemical reactions. This is believed the first observation of laser-induced multiple-colors in the given polymer matrix. It is believed that the colorants underwent photo-effected electron transfer with suitable electron donors from the polymers to change from colorless bipyridilium Bipm²⁺ to the colored Bipm⁺ species. The discovery may lead to new approaches to the development of laser-evoked multiple coloration in polymers.

Keywords: Laser-evoked; Polymer; Color

Phosphorous passivation of In_0.53Ga_0.47As using MOVPE and characterization of Au–Ga₂O₃(Gd₂O₃)–In_0.53Ga_0.47As MIS capacitor by S. Pal; S.M. Shivaprasad; Y. Aparna; B.R. Chakraborty (pp. 196-201).

A study of phosphorous passivation of the interface states of undoped In_0.53Ga_0.47As has been carried out. Phosphorous surface passivation has been achieved by: (1) exchange reaction of the InGaAs surface under phosphine vapor or (2) direct growth of InGaP/GaP thin epitaxial layers in a metal organic vapour phase epitaxy (MOVPE) reactor. The passivated surfaces have been characterized using X-ray photoelectron spectroscopy and capacitance–voltage measurements of the MIS devices. The minimum interface state density of 2.90×10¹¹eV⁻¹cm⁻² was obtained for Au/Ga₂O₃(Gd₂O₃)/GaP/In_0.53Ga_0.47As structure.

Keywords: In; _0.53; Ga; _0.47; As; Surface passivation; Interface state density; XPS; C; –; V; measurement

Deposition of PTFE thin films by RF plasma sputtering on 〈100〉 silicon substrates by Dhananjay S. Bodas; A.B. Mandale; S.A. Gangal (pp. 202-207).

Polymers have been studied extensively due to the wonderful array of properties presented by them. Polymer materials can be coated/deposited by various techniques like sputtering (magnetron, ion beam, RF or dc), plasma polymerization, etc. and can be used in coatings, paint industries, etc. The present study deals with the RF sputter deposition of poly(tetrafluoro ethylene) (PTFE), commonly known as Teflon. Depositions were carried out on mirror polished silicon 〈100〉 substrates at different powers in the range of 100–200W. The deposition time was kept constant at 60min. The sputtered film shows lower contact angle of 50° with water and 44° with diiodomethane, a lower interfacial tension value of 0.76dyne/cm, indicating hydrophilicity and good adhesion of the film with the substrate. FTIR indicates presence of CF, CF₂ bonding groups in the deposited film. Further, XPS study shows presence of CF₃ (292.2eV), CF₂ (290.8eV), C−F (288.0eV) and CCF (286.4eV) moieties indicating deposition of PTFE films at higher power levels of plasma.

Keywords: PACS; 52.75.Rx; 68.55.a; 82.65.i; 82.80.PvPTFE; RF plasma sputtering; XPS; FTIR; Contact angle measurement

Epitaxial growth of tetracene on the Ag(110) surface by B. Lu; H.J. Zhang; H. Huang; H.Y. Mao; Q. Chen; H.Y. Li; P. He; S.N. Bao (pp. 208-214).

Thin film growth of tetracene on Ag(110) has been investigated by using scanning tunneling microscopy (STM). In the monolayer regime, the tetracene molecules formed islands of ordered structure, which is commensurate (4-fold periodicity) in the[11�0] direction, but incommensurate in the [001] azimuth, with the substrate. All the tetracene molecules align regularly with their longer axes parallel to the [001] direction, and with their molecular planes parallel to the surface. At multilayer coverages, the tetracene molecules form a crystalline film in a novel 3D orthorhombic structure, with their orientations remained unchanged. Growth of tetracene on Ag(110) is in the layer-by-layer growth mode.

Keywords: PACS; 68.35.Bs; 61.66.Hq; 61.16.ChOrganic semiconductor; Silver surface; Epitaxial growth; Scanning tunneling microscopy

Corrosion behavior of carbon-implanted M5 alloy in 1M H₂SO₄ by D.Q. Peng; X.D. Bai; B.S. Chen (pp. 215-222).

In order to study the effect of carbon ion implantation on the aqueous corrosion behavior of M5 alloy, specimens were implanted with carbon ions with fluence ranging from 1�10¹⁶ to 1�10¹⁷ions/cm², using a metal vapor vacuum arc source (MEVVA) at an extraction voltage of 40kV. The valence states and depth distributions of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES), respectively. Transmission electron microscopy (TEM) was used to examine the microstructure of the carbon-implanted samples. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the carbon ion implantation. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted M5 alloy in a 1M H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of M5 alloy implanted with carbon ions. The higher the fluence, the better is the corrosion resistance. Finally, the mechanism of the corrosion behavior of carbon-implanted M5 alloy was discussed.

Keywords: M5 alloy; Corrosion resistance; Carbon ion implantation; X-ray photoemission spectroscopy (XPS); Auger electron spectroscopy (AES)

Characterization of PNIPAAm photografted on PET and PS surfaces by Priscila S. Curti; M�rcia R. de Moura; Wanderley Veiga; Eduardo Radovanovic; Adley F. Rubira; Edvani C. Muniz (pp. 223-233).

Aqueous solution of poly( N-isopropylacrylamide), or PNIPAAm, possess lower critical solution temperature (LCST) around 32–33°C. Below this temperature the PNIPAAm is hydrophilic and above presents hydrophobic characteristics. In this work, virgin or oxidized films of PET and PS were submitted to surface modification by grafting of PNIPAAm. The film was immersed in aqueous solution of monomer and exposed to radiation from a low pressure Hg lamp (215W) using KIO₄ as photosensitizer. Virgin, oxidized and PNIPAAm-grafted surfaces were characterized by drop water contact angle (DWCA), SEM, AFM, nanoindentation and XPS techniques. When the grafted polymers are warmed to temperatures above LCST, significant change on DWCA indicates the hydrophilic-to-hydrophobic transition. SEM and AFM images showed a rising of defects and roughness on oxidized and grafted polymer surfaces, compared to the virgin ones. Results from nanoindentation showed that the oxidation process does not produce significant alteration on mechanical properties. However, the PNIPAAm-grafting into PET decreased the hardness and the elastic modulus of such surfaces. XPS analysis indicates significant alterations on atomic composition at surface of polymers, due to the PNIPAAm-grafting. The degrees of grafting were calculated from the relative compositions of nitrogen. The fraction of polymer surface covered by PNIPAAm was, at maximum 0.76. The grafting of PNIPAAm on PET and PS, as investigated in this work, enables the surfaces to be applied as biomaterials, for instance, as substrates for adhesion, growth and detachment of cells.

Keywords: Photografting of PNIPAAm; Photografting on PET surfaces; Photografting on PS surfaces; PNIPAAm

Optically variable imaging using nanoimprint technique by V. Grigaliūnas; D. Jucius; S. Tamulevi�?ius; A. Guobienė; V. Kopustinskas (pp. 234-239).

Imprint technique was successfully applied for the creation of optically variable diffractive images by combining direct imprint of single oriented grating, forming of desired graphic art with a set of polished stamps and reactive ion etching. Fidelity of the etching mask as well as shape of the grating transferred into the silicon substrate was analyzed by atomic force microscope. Problems, which occur during the fabrication process, are discussed. As a result, optically variable image composed of three orientations of gratings is presented. Proposed technique could find further application in the origination of not too complicated diffraction graphic arts suitable for document security applications.

Keywords: Nanoimprint lithography; Diffraction gratings; Optically variable imaging

Pressure dependence of radical densities in various gas discharges by Min Tae Kim (pp. 240-251).

Pressure dependence of radical densities in various gas discharges is investigated using a simple plasma kinetics model. Modifications and corrections were made to the previous formulation of the model. For this purpose the dissociation degree of feed gas was addressed in terms of the pressure, and empirical expressions for the dissociation degree were suggested for further analysis. Some speculations on the lifetime of the radicals in the discharge for mixed gas discharges were also made. Experimental data presented in the literature were analyzed based on this modified and corrected model. The validity of the model for a global application was testified by comparing the expectations of the model with the experimental result published in the literature.

Keywords: Pressure dependence; Radical densities; Gas discharges

Dispersion of nonaqueous Co₂Z ferrite powders with titanate coupling agent and poly(vinyl butyral) by Hsing-I Hsiang; Chih-Cheng Chen; Jaw-Yue Tsai (pp. 252-259).

Co₂Z ferrite powders with the chemical composition 3Ba_0.5Sr_0.5O·2CoO·12Fe₂O₃ have superior high frequency magnetic properties. However, Co₂Z ferrite powders are difficult to apply to practical processes because of agglomeration induced by the strong magnetic attraction between particles. In this study, Co₂Z ferrite powders pretreatment using a titanate coupling agent – neopentyl(dially)oxy tri(dioctyl)pyrophosphate titanate (Lica 38) on the sedimentation and rheological behavior is investigated.The bonding mechanisms between ferrite powder, Lica 38, and poly(vinyl butyral) (PVB) are studied using diffuse reflectance Fourier transform infrared spectroscopy is used to explain the difference in the rheological and sedimentation behaviors of untreated and titanate coupling agent-modified ferrite powders.The affinity of Co₂Z ferrite and PVB could be substantially enhanced by coating a titanate coupling agent onto the ferrite surface. The coated layer could prevent particles from agglomeration induced by the magnetic interaction.

Keywords: Co; ₂; Z ferrites; Titanate coupling agent; Dispersion; FTIR

Surface analysis of the proton exchange membranes prepared by pre-irradiation induced grafting of styrene/divinylbenzene into crosslinked thin PTFE membranes by Jingye Li; Shogo Ichizuri; Saneto Asano; Fumihiro Mutou; Shigetoshi Ikeda; Minoru Iida; Takaharu Miura; Akihiro Oshima; Yoneho Tabata; Masakazu Washio (pp. 260-272).

The proton exchange membranes were obtained by pre-irradiation induced grafting of styrene with or without divinylbenzene (DVB) into thin crosslinked polytetrafluoroethylene (RX-PTFE) membranes with the thickness around 10μm and successive sulfonation. The surface chemical structure and morphology of the non-grafted, the grafted, and the grafted and sulfonated RX-PTFE membranes were studied by means of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis. From the F/C atom ratio result, it was known that there are mainly polystyrene grafts on the surfaces of the styrene grafted RX-PTFE membranes, while there are mainly PTFE chains on the surfaces of the RX-PTFE membranes grafted by styrene together with DVB. “Wave�? shape morphology on the surfaces of the grafted RX-PTFE membranes was observed. The F/C atom ratios on the surfaces of the grafted and sulfonated membranes are little lower than the corresponding grafted membranes before sulfonation. On the surface of the sulfonated membranes, the “wave�? shape morphology was also observed. The distributions of the polystyrene grafts in the RX-PTFE membranes matrixes were strongly affected by the concentration of the crosslinking co-monomer, DVB, used in the graft polymerization, and the sulfonation will not change the distribution of the grafts obviously.

Keywords: Proton exchange membrane; Crosslinked polytetrafluoroethylene; Pre-irradiation induced graft polymerization; Styrene/divinylbenzene; Surface analysis

The effect of the oxygen concentration and the rf power on the zinc oxide films properties deposited by magnetron sputtering by I. Sayago; M. Aleixandre; L. Ar�s; M.J. Fern�ndez; J.P. Santos; J. Guti�rrez; M.C. Horrillo (pp. 273-280).

The influence of the oxygen concentration and the rf power variation on the zinc oxide films structural properties were studied. ZnO films were deposited on silicon substrate by rf magnetron sputtering in reactive plasma using a zinc oxide target.Crystalline structures and roughness characteristics of the films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements, respectively. Deposition conditions were optimized to obtain films of good quality suitable for the fabrication of surface acoustic wave (SAW) devices. The optimal parameters to obtain a good piezoelectric material have been: rf power 50W and reactive plasma.

Keywords: PACS; 81.15.Cd; 77.84.−s; 85.50.+kZnO; Piezoelectric material; Magnetron sputtering; Atomic force microscopy; X-ray diffraction

Growth mode during initial stage of chemical vapor deposition by Yuya Kajikawa; Suguru Noda (pp. 281-289).

The initial stage during vapor deposition has been extensively studied in physical vapor deposition (PVD) processes, and nucleation theories have been successfully used to model island nucleation processes during PVD. Compared with the extensive research in PVD, there has been less work on understanding the initial stage in chemical vapor deposition (CVD) processes, despite the technological and commercial importance of CVD-based manufacturing systems. In this work we briefly review the nucleation theories developed for PVD processes and consider the validity of them for modeling the initial stage of CVD processes. One characteristic of CVD processes is the existence of an incubation time. Recent research indicates that the incubation time can be caused by the different reactivity of precursors nucleating on substrates and islands. We proposed process indices to evaluate the relative importance of sticking probabilities and desorption of adsorbates on the incubation time. The differing precursor reactivity between islands and substrates may also affect the island growth mode. This situation in CVD processes differs from that in PVD processes, for which current nucleation theories were developed, and therefore prevents the direct application of PVD nucleation theories to CVD processes. Therefore, to model CVD processes, a nucleation model is needed that is sensitive to the different reactivity of precursors to islands and substrates.

Keywords: Chemical vapor deposition; Physical vapor deposition; Growth mode; Nucleation; Nanoparticle

Design and development of artificial neural networks for depositing powders in coating treatment by Ming-Der Jean; Chyuan-Du Liu; Jen-Ting Wang (pp. 290-303).

We propose the application of an artificial neural network to a Taguchi orthogonal experiment to develop a robust and efficient method of depositing alloys with a favorable surface morphology by a specific microwelding hardfacing process. An artificial neural network model performs self-learning by updating weightings and repeated learning epochs. The artificial neural network construct can be developed based on data obtained from experiments. The root of mean squares (RMS) error can be minimized by applying results obtained from training and testing samples, such that the predicted and experimental values exhibit a good linear relationship. An analysis of variance indicates that the significant factors explain approximately 70% of the total variance. Consequently, the Taguchi-based neural network model is experimentally confirmed to estimate accurately the hardfacing roughness performance.The experimental results reveal the hardfacing roughness performance of the product of PTA coating is greatly improved by optimizing the coating conditions and is accurately predicted by the artificial neural network model. The combination of the neural network model with Taguchi-based experiments is demonstrated as an effective and intelligent method for developing a robust, efficient, high-quality coating process.

Keywords: PACS; Deposition films and coatings, 81.15; Plasma applications, 81.15.G; Artificial intelligence, 07.05.MArtificial neural network (ANN); Plasma transfer arc (PTA); Deposited alloy; Analysis of variance (ANOVA); Root of mean squares (RMS)

Mesoporous silica thin films prepared by argon plasma treatment of sol–gel-derived precursor by Jian Zhang; Alagappan Palaniappan; Xiaodi Su; Francis E.H. Tay (pp. 304-309).

Argon plasma is used to generate the mesoporous silica thin films from sol–gel-derived precursor. Poly(ethylene glycol) (PEG, MW=400) is employed as the template, i.e., the pore-directing agent as well as the binder. The influence of the plasma parameters (plasma power and processing time) on the mesoscopic properties of silica films are investigated by scanning electron microscopy (SEM), FT-IR, low-angle X-ray scattering (SAXS), and nitrogen adsorption isotherm. It is concluded that the plasma treatment is a promising way to remove organic templates and generate mesoporous thin films. Compared to the conventional thermal calcination methods, the plasma treatment provides a promising low-temperature, low-cost and time-saving preparation process.

Keywords: PACS; 81.05.Gc; 82.33.Xj; 73.50.Mx; 52.77.Dq; 68.60.DvSol–gel; Silica; Mesoporous; Argon plasma; PEG template

Thickness dependence of properties of ZnO:Ga films deposited by rf magnetron sputtering by Xuhu Yu; Jin Ma; Feng Ji; Yuheng Wang; Chuanfu Cheng; Honglei Ma (pp. 310-315).

Gallium-doped zinc oxide (ZnO:Ga) films are prepared on glass substrates by rf magnetron sputtering at room temperature. The structural, electrical and optical properties of the ZnO:Ga films with various thickness are studied in detail. The crystal structure of the ZnO:Ga films is hexagonal wurtzite. The orientation for all the obtained films is along the c-axis perpendicular to the substrate. It is observed that with an increase in film thickness, the crystallite sizes of the films are increased. The lowest electrical resistivity among the films is found to be about 3.1×10⁻⁴Ωcm and the average transmittance for all films including substrates is over 83% in the visible range.

Keywords: PACS; 68.55Gi; 73.60.Cs; 78.30.FsZnO:Ga; Magnetron sputtering; Film thickness; Electrical and optical properties

Laser surface modified ductile iron by pulsed Nd:YAG laser beam with two-dimensional array distribution by Y. Chen; C.H. Gan; L.X. Wang; G. Yu; A. Kaplan (pp. 316-321).

A novel modification layer on the surface of pearlite-ferrite matrix ductile iron was fabricated under irradiation of Nd:YAG laser beam equipped with self-designed diffractive optical element (DOE) which produces a 5�5 two-dimensional array distribution at the focal plane. The microstructure of the layer along the surface and the direction of the layer depth had obvious gradient distribution, and therefore the two-dimensional microhardness map of the layer alternated higher hardness with lower hardness. The results showed that the novel modification layer is expected to have excellent combination of strength and toughness.

Keywords: PACS; 75.50.B; 61.80.B; 42.79Ductile iron; Nd:YAG laser; Laser surface modification; Diffraction optical element (DOE)

CdO thin films: a study of their electronic structure by electron spin resonance spectroscopy by Antonino Gulino; Giovanni Tabb� (pp. 322-327).

The Cd(C₅F₆HO₂)₂·polyether adducts were used in MOCVD experiments of cadmium oxide, on optical transparent SiO₂ substrates. Very mild heating (44–74°C) resulted in, thermal stable, liquid compounds that can be easily evaporated. XRD measurements provided evidence of cubic highly textured CdO(100) films. The surface atomic composition was investigated by XPS analysis. UV–vis spectra showed that the transmittance of as-deposited films in the visible region is about 90%. Resistivity measurements of CdO thin films showed that they are highly conducting. ESR analysis suggests the presence of Cd⁺ ions, on the site of Cd²⁺, arising from polaronic self-trapping of electrons introduced by oxygen deficiency at Cd²⁺ sites to generate localised 5s¹ states.

Keywords: CdO; ESR; MOCVD; Film

Chemical deposition and characterization of copper indium diselenide (CISe) thin films by H.M. Pathan; C.D. Lokhande (pp. 328-334).

Copper indium diselenide (CISe) thin films were chemically deposited using modified chemical bath deposition (M-CBD) from solutions of (CuSO₄+In₂(SO₄)₃) and Na₂SeSO₃ as cationic and anionic sources, respectively. M-CBD is based on the immersion of the substrate into separately placed cationic and anionic precursors. Attempt was made to prepare the CISe films at room temperature. The films were characterized for their structural, morphological, compositional and electrical properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Rutherford back scattering (RBS) and electrical measurement techniques.

Keywords: CuInSe; ₂; Chemical deposition; Physio-chemical characterization

Laser conditioning and multi-shot laser damage accumulation effects of HfO₂/SiO₂ antireflective coatings by Yuanan Zhao; Tao Wang; Dawei Zhang; Jianda Shao; Zhengxiu Fan (pp. 335-339).

Laser conditioning effects of the HfO₂/SiO₂ antireflective (AR) coatings at 1064nm and the accumulation effects of multi-shot laser radiation were investigated. The HfO₂/SiO₂ AR coatings were prepared by E-beam evaporation (EBE). The single-shot and multi-shot laser induced damage threshold was detected following ISO standard 11254-1.2, and the laser conditioning was conducted by three-step raster scanning method. It was found that the single-shot LIDT and multi-shot LIDT was almost the same. The damage mostly >80% occurred in the first shot under multi-shot laser radiation, and after that the damage occurring probability plummeted to <5%. There was no obvious enhancement of the laser damage resistance for both the single-shot and multi-shot laser radiation of the AR coatings after laser conditioning. A Nomarski microscope was employed to map the damage morphology, and it found that the damage behavior is defect-initiated for both unconditioned and conditioned samples.

Keywords: Antireflective coatings; Laser conditioning; Single-shot; Multi-shot; Laser-induced damage threshold; Accumulation effects; Defect; Damage morphology

Influence of sulfidation ambience on the properties of nanocrystalline ZnS films prepared by sulfurizing the as-sputtered ZnO films by Rengang Zhang; Baoyi Wang; Hui Zhang; Long Wei (pp. 340-345).

Nanocrystalline ZnS films have been prepared on glass and quartz substrates by sulfurizing the as-sputtered ZnO films at 500�C in H₂S or sulfur-vapor. The films are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive analysis of X-ray (EDX) and UV-visible transmission spectra. It is found that the total conversion of ZnO films in sulfur-vapor to the hexagonal ZnS films requires 11h much longer than that in H₂S, due to the low S content in sulfur-vapor. And the high ZnS (0 0 2) preferred orientation can be observed for ZnS films formed in H₂S or low pressure sulfur-vapor. The results also show that ZnS films formed in sulfur-vapor have about 200nm grains greater than those formed in H₂S, because the solid-phase recrystallization during the sulfidation process is favorable in sulfur-vapor. Besides, the great broadening of the absorption edge in the optical transmission spectra, and the small band-gap energies compared to that of ZnS films formed in H₂S, are obtained for ZnS films produced in sulfur-vapor, which can arise from existence of some ZnO and residual sulfur phase, and sulfur interstitial atoms in the films.

Keywords: PACS; 78.66.HfZnS films; ZnO films; Sulfidation

Corrosive sliding wear behavior of laser clad Mo₂Ni₃Si/NiSi intermetallic coating by X.D. Lu; H.M. Wang (pp. 346-352).

Many ternary metal silicides such as W₂Ni₃Si, Ti₂Ni₃Si and Mo₂Ni₃Si with the topologically closed-packed (TCP) hP12 MgZn₂ type Laves phase crystal structure are expected to have outstanding wear and corrosion resistance due to their inherent high hardness and sluggish temperature dependence and strong atomic bonds. In this paper, Mo₂Ni₃Si/NiSi intermetallic coating was fabricated on substrate of an austenitic stainless steel AISI321 by laser cladding using Ni–Mo–Si elemental alloy powders. Microstructure of the coating was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS). Wear resistance of the coating is evaluated under corrosive sliding wear test condition. Influence of corrosion solutions on the wear resistance of the coating was studied and the wear mechanism was discussed based on observations of worn surface morphology. Results showed that the laser clad Mo₂Ni₃Si/NiSi composite coating have a fine microstructure of Mo₂Ni₃Si primary dendrites and the interdendritic Mo₂Ni₃Si/NiSi eutectics. The coating has excellent corrosive wear resistance compared with austenitic stainless steel AISI321 under acid, alkaline and saline corrosive environments.

Keywords: Laser cladding; Metal silicide; Mo; ₂; Ni; ₃; Si; Corrosive wear; Coating

Dip coating of dielectric and solder mask epoxy polymer layers for build-up purposes by Sam Siau; Alfons Vervaet; Siska Degrande; Etienne Schacht; Andre Van Calster (pp. 353-368).

Polymer coatings used as build-up layers in advanced printed circuit boards (PCBs) are usually applied through curtain coating or lamination for industrial purposes. Dip coating can be used as an easier and cheaper way of applying a build-up layer, in particular for research purposes, because of the relative high viscosity of liquid polymer solutions used for build-up layers or solder mask layers. The thickness of the deposited layer is examined on different substrates and can be varied with great ease and small variance by changing the pull-out speed. The experimental thickness of the coated layer is compared to various models existing in literature. The deposited polymer layers show a thickening effect in comparison to the Landau and Levich theory. This thickening effect depends on the properties of the polymer solution and the substrate on which the polymer layer is applied. The coated thickness of polymer solutions is influenced by a number of phenomena, such as normal stresses, non-Newtonian viscosity effects and influences of gravity. More practical empirical thickness models are developed and fitted. Polymer solutions containing inorganic filler particles show a different coating behavior in comparison to polymer solutions containing no filler particles.

Keywords: PACS; 81.15.-zPolymer coatings; Build-up layer; Dip coating

X-ray study of structural reorganization in phthalocyanine containing Langmuir–Blodgett heterostructures by Victor Erokhin; Sandro Carrara; Cristina Paternolli; Larisa Valkova; Sigrid Bernstorff; Claudio Nicolini (pp. 369-375).

Langmuir–Blodgett heterostructures containing phthalocyanine and fatty acid salt multilayers were studied by X-ray scattering using synchrotron radiation. Two structural reorganizations of the film were registered after the thermal treatment. The first phase transition took place after heating till the melting point of the fatty acid and the second one, at a higher temperature, but before the phthalocyanine melting point. Models of the molecular organization for all three film packings were suggested.

Keywords: Phthalocyanines; Langmuir–Blodgett heterostructures; Small angle X-ray scattering

Effects of Cr and Nb doping on the ferroelectricity of chemical-solution-deposited Bi_3.5Nd_0.5Ti₃O₁₂ films by Tian-Lin Chang; Wen-Tai Lin (pp. 376-383).

The effects of Cr and Nb doping and annealing processing on the microstructure and ferroelectricity of Bi_3.5Nd_0.5Ti₃O₁₂ (BNT) films deposited by chemical-solution method were studied. The BNT films deposited from 0.05M solutions showed larger grain size and thus better ferroelectricity than those deposited from 0.075M solutions. For the Cr-doped BNT (BNTC x) films only Cr³⁺ substitutionally incorporated into the Ti⁴⁺ site of the TiO₆ octahedron. Cr doping could result in the increase of the number of oxygen vacancies, reduction of the grain size, and enhancement of c-axis oriented growth, leading to the degradation of the remanent polarization (2Pr) of BNTC x films. For the Nb-doped BNT (BNTN x) films the 2Pr first increased from 40μC/cm² at x=0–43μC/cm² at x=0.005 and then decreased with increasing the Nb concentration ( x) in the range of 0.01–0.1. The Nb cations substitutionally incorporated into the Ti⁴⁺ site of the BNT lattice were in the state of Nb⁵⁺, which could reduce the amount of oxygen vacancies and thus improve the 2Pr. The doping of Nb⁵⁺ into the BNT films could induce four effects on the 2Pr, i.e., reducing the amount of oxygen vacancies, reducing the grain size, enhancing the (100)/(010)-oriented growth, and possibly changing the lattice distortion of the TiO₆ octahedron.

Keywords: BiNdTiO films; Ion doping; FerroelectricityPACS; 61.72.Ww; 77.80.−e; 77.84.Bw; 81.15.Lm

Effect of thermal annealing on the optical and electronic properties of ZnO thin films grown on p-Si substrates by W.G. Han; S.G. Kang; T.W. Kim; D.W. Kim; W.J. Cho (pp. 384-390).

The effects of annealing on the optical and the electronics properties of ZnO thin films grown on p-Si(100) substrates by using radio frequency magnetron sputtering were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) measurements. The XRD patterns and pole figures showed that the crystallinity of the ZnO films grown on p-Si(100) substrates was improved by thermal treatment. XRD patterns, pole figures, and TEM images showed that the as-grown and the annealed ZnO films grown on Si(100) substrates had a c-axis preferential orientation in the [0001] crystal direction. The PL spectra showed that luminescence peaks related to the free excitons and the deep levels appeared after annealing. The XPS spectra showed that the peak positions corresponding to the O 1s and the Zn 2p shifted slightly after thermal treatment. These results can help improve understanding of thermal effects on the optical and the electronic properties of ZnO thin films grown on p-Si(100) substrates.

Keywords: PACS; 61.10.−l; 68.37.LpZnO/p-Si; Thermal annealing; Optical properties; Electronic properties

Photoluminescence and characteristics of terbium-doped AlN film prepared by magnetron sputtering by F.S. Liu; W.J. Ma; Q.L. Liu; J.K. Liang; J. Luo; L.T. Yang; G.B. Song; Y. Zhang; G.H. Rao (pp. 391-399).

Tb-doped AlN films are prepared by reactive radio frequency (RF) magnetron sputtering under different work conditions. As the RF power increases from 50 to 250W, the prepared film changes from amorphous to c-axis oriented crystalline. Lower work pressure and higher RF power enhance the deposition rate and crystallinity. The emission from⁵D₄ to⁷F_J ( J=6–0) of Tb³⁺ are observed on all the films. The intensity of PL spectra of crystalline films is obviously stronger than that of the amorphous films. The PL intensity of⁵D₄ to⁷F₆ is the strongest for crystalline film, but for amorphous film that of⁵D₄ to⁷F₅ is the strongest. Time-resolved spectra show that there exist two decay time for⁵D₄ to⁷F_J ( J=6, 5): one is shorter ranging from 41 to 60μs, the other is longer ranging from 202 to 287μs. The decay time of amorphous film is slightly longer than that of crystalline films.

Keywords: PACS; 61.10.Nz; 61.66.Fn; 78.55.HxPhotoluminescence; Tb-doped; Aluminum nitride; Film

Calculation of the emission performance of the carbon nanotube array by Zhang Yuning; Lei Wei; Zhang Xiaobing; Wang Baoping (pp. 400-406).

Because of the excellent field emission performances, the carbon nanotube array has already been used as the cold electron source in the field emission display, the vacuum microwave tube, and the electron microscopy, etc. It is necessary to estimate the emission performance of the carbon nanotube array in the design of these devices. The emission current density of a single carbon nanotube can be estimated with the Fowler–Nordheim formula approximately. Thus, the emission performance of the whole array is obtained by the sum of the current emitted from all carbon nanotubes in the array. However, this calculation is very complex and time consuming due to the large number of carbon nanotubes in the array. This paper proposes a simple model to predict the emission performance of the whole CNT array. The total emission current can be deduced easily with this model if we know the geometrical parameters of the CNT array. A few experiments have been performed to verify this model. With this model, the influences of geometric dimensions of the CNT array on the emission performance are also discussed.

Keywords: PACS; 81.40.Rs; 79.60.Jv; 85.45.DbEmission performance; CNT array; Geometrical dimension

Hydrophobic and textured ZnO films deposited by chemical bath deposition: annealing effect by V.R. Shinde; C.D. Lokhande; R.S. Mane; Sung-Hwan Han (pp. 407-413).

Highly textured ZnO cones have been grown onto glass substrates by chemical bath deposition (CBD) method. They were given heat treatment at 623K for 2h in air. The change in structural, optical and electrical properties were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption, electrical resistivity and contact angle measurements. Structural analysis by X-ray diffraction pattern showed as-deposited ZnO film has high-orientation along c-direction (002), which remained the same with low-intensity after heat treatment. Well-defined cones almost perpendicular to substrate surface, which were slightly compressed in size after heat treatment, have been detected through SEM micrographs. Water wettability study revealed a contact angle of 72.28±1.5° for as-deposited ZnO films, whereas hydrophobic surface with a contact angle of 152.84±1.5° was obtained after heat treatment. This is attributed to the topographical change in structural morphology. Change in bandgap energy from 3.7 to 3.2eV was observed after heat treatment. Electrical resistivity measurement showed semiconducting nature with room temperature resistivity 10⁴Ωcm for as-deposited ZnO, which was decreased to 10³Ωcm for annealed ZnO film.

Keywords: ZnO cones; CBD; Annealing effect; Contact angle; Optical absorption; Electrical resistivity

Characteristics and luminescence of Ge doped ZnO films prepared by alternate radio frequency magnetron sputtering by D.H. Fan; Z.Y. Ning; M.F. Jiang (pp. 414-419).

Ge doped ZnO films have been deposited on Si(100) substrates by alternate rf sputtering of ZnO and Ge. The effects of doping and annealing on the optical and structural properties have been investigated by means of X-ray diffraction and photoluminescence (PL) spectra. With the increasing annealing temperature, the intensity of the ZnO(002) diffraction peak increases, indicating that the crystalline quality of the film improves. The samples annealed at 800 and 1000�C there appear the GeO and GeO₂ diffraction peaks, and the intensity of the near ultra-violet emission at 395nm increases greatly, while a weak yellow emission appears at 590nm. The near ultra-violet emission could be attributed to the GeO color centers and exciton recombination. The yellow peak is probably related to Ge incorporated in the ZnO structure.

Keywords: PACS; 72.80.Tm; 81.15.cd; 78.55.−mGe doped ZnO films; Rf sputtering; Photoluminescence

Laser processing of diamond-like carbon–metal composites by Roger Jagdish Narayan (pp. 420-430).

Diamond-like carbon (DLC) is a hydrogen-free amorphous material that contains a large fraction of sp³-hybridized carbon atoms. DLC exhibits hardness, corrosion resistance, and wear resistance properties close to those of diamond. Unfortunately, DLC films contain a large amount of compressive stresses and exhibit poor adhesion to many metal substrates. We have adopted a novel pulsed laser deposition process to incorporate metal atoms into diamond-like carbon films. Visible Raman spectroscopy data suggest that DLC–metal composite films possess less internal compressive stress than as-prepared DLC films. DLC–metal composite films have several potential applications, including use in machine tools and medical prostheses.

Keywords: PACS; 81.05.UwPulsed laser deposition; Diamond-like carbon; Scanning transmission electron microscopy

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Applied Surface Science (v.245, #1-4)