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Applied Surface Science (v.254, #5)

Tip-induced local anodic oxidation on p-GaAs surface with non-contact atomic force microscopy by Chien-Huang Tsai; Sheng-Rui Jian; Hua-Chiang Wen (pp. 1357-1362).

Nano-sized oxide structures resulted from localized electrochemical oxidation induced by a negatively biased atomic force microscopy (AFM) tip operated with the non-contact mode were fabricated on p-GaAs(100) surface. The geometrical characteristics of the oxide patterns and their dependences on various fabrication parameters, e.g., the anodization time, the biased voltages, the tip scanning rates, as well as the formation mechanism and relevant growth kinetics are investigated. Results indicate that the height of the protruded oxide dots grow exponentially as a function of time in the initial stage of oxidation and soon reaches a maximum height depending linearly with the anodized voltages, in according with the behaviors predicted by space charge limited local oxidation mechanism. In addition, selective micro-Auger analysis of the anodized region reveals the formation of Ga(As)O_x, indicating the prominent role played by the field-induced nanometer-size water meniscus in producing the nanometer-scale oxide dots and bumps on p-GaAs(100) surface.

Keywords: PACS; 68.37.−d; 68.37.Ps; 68.37.Xy; 81.05.Ea; 82.45.YzAFM; Nano-oxidation; GaAs; Auger electron spectroscopy

Nd:YAG laser synthesis of nanostructural V₂O₅ from vanadium oxide sols: Morphological and structural characterizations by S. Beke; L. Kőrösi; S. Papp; L. Nánai; A. Oszkó; J.G. Kiss; V. Safarov (pp. 1363-1368).

Vanadium oxide thin films were prepared by sol–gel method, then subjected to Nd:YAG laser (CW, 1064nm) radiation. The characteristics of the films were changed by varying the intensity of the laser radiation. The nanocrystalline films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). XRD revealed that above 102W/cm² the original xerogel structure disappears and above 129W/cm² the films become totally polycrystalline with an orthorhombic structure. From TEM observations, we can see that due to laser radiation, the originally fibrillar-like particles disappear and irregular shaped, layer structured V₂O₅ particles are created. From XPS spectra we can conclude that due to laser radiation the O/V ratio increased with higher intensities.

Keywords: Vanadium oxide thin films; Sol–gel process; Laser radiation; X-ray diffraction; X-ray photoelectron spectroscopy; TEM; SEM

Write-once blue laser recording using silicon doped SbO_x thin films prepared by reactive dc-magnetron sputtering by Ying Zhou; Yongyou Geng; Donghong Gu; Qing Zhu; Zhi Jiang (pp. 1369-1372).

Si:SbO_x films have been deposited by reactive dc-magnetron sputtering from a Sb target with Si chips attached in Ar+O₂ with the relative O₂ content 7%. The as-deposited films contained Sb metal, Sb₂O₃, SiO, Si₂O₃ and SiO₂. The crystallization of Sb was responsible for the changes of optical properties of the films. The results of the blue laser recording test showed that the films had good writing sensitivity for blue laser beam (406.7nm), and the recording marks were still clear even if the films were deposited in air 60 days, which demonstrated that doping silicon in SbO_x films can improve the stability of SbO_x films. High reflectivity contrast of about 36% was obtained at a writing power 6mW and writing pulse width 300ns.

Keywords: PACS; 78.66.−w; 78.20.−e; 81.15.Cd; 81.40.TvSi:SbO; _x; films; Blue laser; Write-once; Optical recording materials

Thermal process and surface damage of GaAs induced by 532nm continuous laser by Haifeng Qi; Qingpu Wang; Yongfu Li; Xingyu Zhang; Zejin Liu; Yurong Wang; Sasa Zhang; Wei Xia; Guofan Jin (pp. 1373-1376).

The thermal damage process of gallium arsenide (GaAs) induced by 532nm continuous laser is presented in this work. The surface damage in the form of decomposing was detected and determined previous to the melting damage by the real-time observation of surface reflectivity. The evaporation of As induced the decrease of As content in the irradiated surface. The microscopic morphology and composition analysis of the damaged surfaces at different moments during the whole thermal process were performed with an electron probe microscope.

Keywords: PACS; 68.60.Dv; 79.20.DsLaser induced damage (LID); Gallium arsenide (GaAs); Thermal damage; Thermal process; Continuous laser

Periodic surface structures on crystalline silicon created by 532nm picosecond Nd:YAG laser pulses by M.S. Trtica; B.M. Gakovic; B.B. Radak; D. Batani; T. Desai; M. Bussoli (pp. 1377-1381).

Creation of laser-induced morphology features, particularly laser-induced periodic surface structures (LIPSS), by a 532nm picosecond Nd:YAG laser on crystalline silicon is reported. The LIPSS, often termed ripples, were produced at average laser irradiation fluences of 0.7, 1.6, and 7.9Jcm⁻². Two types of ripples were registered: micro-ripples (at micrometer scale) in the form of straight parallel lines extending over the entire irradiated spot, and nano-ripples (at nanometer scale), apparently concentric, registered only at the rim of the spot, with the periodicity dependent on laser fluence. There are indications that the parallel ripples are a consequence of the partial periodicity contained in the diffraction modulated laser beam, and the nano-ripples are very likely frozen capillary waves. The damage threshold fluence was estimated at 0.6Jcm⁻².

Keywords: PACS; 79.20.DsSurface modification; Micro-ripples; Nano-ripples; Silicon; Picosecond laser

Improvement in mechanical and optical properties of vapour chopped vacuum evaporated PANI/PMMA composite thin film by J.B. Yadav; R.K. Puri; Vijaya Puri (pp. 1382-1388).

PANI/PMMA composite was synthesized by emulsion polymerization pathway and the composite thin film was obtained by vacuum evaporation. The effect of vapour chopping and varying PMMA concentration was also studied. The FTIR spectra showed that the PANI/PMMA composite thin film deposited as a short chain oligomers. Increase in transmittance and decrease in refractive index was obtained with increasing concentration of PMMA, which further increased the adhesion and decreased intrinsic stress. The vapour chopping improved its optical as well as mechanical properties and produced smoother surface morphology. Increase of PMMA made the film more amorphous and does not change its band gap.

Keywords: PANI/PMMA composite; Vacuum evaporation; Vapour chopping; Thin film; Optical properties; Mechanical properties

Fine-structured field emission images originating from coherently scattering of electrons within a multi-walled carbon nanotube by Ping Wu; S.Z. Deng; Jun Chen; N.S. Xu (pp. 1389-1393).

High resolution field emission image of a single multi-walled carbon nanotube was studied by field emission microscopy. The images contain patterns consisting of rather ordered bright fringes. We propose a model based on coherent electron scattering to explain the observed field emission image. The emitted electrons will undergo coherent scattering within the cap region of a multi-wall carbon nanotube, which may be viewed as elastic scattering by a polycrystalline structure with an infinite size. This study is helpful for understanding the physical mechanism of field emission of carbon nanotube.

Keywords: PACS; 73.63.Fg; 68.37.Vj; 81.05.UwField emission microscopy image; Carbon nanotube; Coherently scattering of electrons

Directly writing with nanoparticles at the nanoscale using dip-pen nanolithography by Debdulal Roy; Martin Munz; Paolo Colombi; Sanjib Bhattacharyya; Jean-Paul Salvetat; P.J. Cumpson; Marie-Louise Saboungi (pp. 1394-1398).

Well-defined nanostructures were written with quantum dots and magnetic nanoparticles on gold and mica surfaces using dip-pen nanolithography at room temperature. The structures with both the nanoparticles were characterised by in situ topography measurements, and the quantum dot structures were mapped by fluorescence mapping. It is demonstrated that structures of various kinds such as dots and lines can be prepared using such nanoparticles on suitably prepared surfaces.

Keywords: Dip-pen nanolithography; Nanoparticles

Catalytic behaviors of ruthenium dioxide films deposited on ferroelectrics substrates, by spin coating process by M. Khachane; P. Nowakowski; S. Villain; J.R. Gavarri; Ch. Muller; M. Elaatmani; A. Outzourhite; I. Luk’yanchuk; A. Zegzouti; M. Daoud (pp. 1399-1404).

Catalytic ruthenium dioxide films were deposited by spin-coating process on ferroelectric films mainly constituted of SrBi₂Ta₂O₉ (SBT) and Ba₂NaNb₅O₁₅ (BNN) phases. After thermal treatment under air, these ferroelectric–catalytic systems were characterized by X-ray diffraction and scanning electron microscopy (SEM). SEM images showed that RuO₂ film morphology depended on substrate nature. A study of CH₄ conversion into CO₂ and H₂O was carried out using these catalytic–ferroelectric multilayers: the conversion was analyzed from Fourier transform infrared (FTIR) spectroscopy, at various temperatures. Improved catalytic properties were observed for RuO₂ films deposited on BNN oxide layer.

Keywords: PACS; 81.20.Fw; 81.15.-z; 68.55.–a; 81.15.Aa; 82.45.Jn; 82.65.-s; 81.16.Hc; 82.80.Gk; 68.65.AcRuthenium dioxide; Sol–gel processing; Multilayer; Infrared spectroscopy; Catalytic measurements

Morphology and natural wettability properties of sol–gel derived TiO₂–SiO₂ composite thin films by M. Houmard; D. Riassetto; F. Roussel; A. Bourgeois; G. Berthomé; J.C. Joud; M. Langlet (pp. 1405-1414).

Previous studies suggest that granular interfaces induce a natural and persistent super-hydrophilicity in TiO₂–SiO₂ composite thin films deposited by sol–gel route. This effect enables to consider self-cleaning applications that do not require a permanent UV exposure, whereas such a permanent exposure is necessary for pure TiO₂ films. In this study, TiO₂–SiO₂ composite thin films have been deposited from a TiO₂ anatase crystalline suspension and different SiO₂ polymeric sols. Wettability studies show that a suitable control of the TiO₂–SiO₂ mixed sol formulations noticeably enhances persistence of the natural super-hydrophilicity in composite films. It is shown that, beside granular interface effects, modifications in the composite film morphologies can noticeably influence wettability properties.

Keywords: Super-hydrophilicity; TiO; ₂; –SiO; ₂; thin films; Sol–gel; Self-cleaning surfaces

Atomic-level simulations of nanoindentation-induced phase transformation in mono-crystalline silicon by Yen-Hung Lin; Tei-Chen Chen; Ping-Feng Yang; Sheng-Rui Jian; Yi-Shao Lai (pp. 1415-1422).

Molecular dynamics (MD) simulations of nanoindentation are carried out to investigate the phase transformations in Si with a spherical indenter. Since the phase transformation induced by deformation in micro-scale is closely related to the carrier mobility of the material, it has become a key issue to be investigated for the chips especially with smaller feature size. Up to now, however, it is not possible to carry out the nanoindentation experimentally in such a small feature. Consequently, molecular dynamic simulation on nanoindentation is resorted to and becomes a powerful tool to understand the detailed mechanisms of stress-induced phase transformation in nano-scale. In this study, the inter-atomic interaction of Si atoms is modeled by Tersoff's potential, while the interaction between Si atoms and diamond indenter atoms is modeled by Morse potential. It is found that the diamond cubic structure of Si in the indentation zone transforms into a phase with body-centred tetragonal structure (β-Si) just underneath the indenter during loading stage and then changes to amorphous after unloading. By using the technique of coordinate number the results reveal that indentation on the (001) surface exhibits significant phase transformation along the <110> direction. In addition, indentation on the (110) surface shows more significant internal slipping and spreading of phase transformation than on the (001) surface. Furthermore, during the indentation process phase transformations of Si are somewhat reversible. Parts of transformed phases that are distributed over the region of elastic deformation can be gradually recovered to original mono-crystal structure after unloading.

Keywords: Molecular dynamics simulations; Nanoindentation; Silicon; Phase transformation; β-Si

Real-time monitoring of diamond nucleation and growth using field-enhanced thermionic emission current by Y.X. Han; M. Zhao; J. Sun; H. Ling; T. Gebre; Y.F. Lu (pp. 1423-1426).

Diamond nucleation and growth in the combustion-flame method were monitored in real time using thermionic emission current from the deposited diamond films. It was observed that the emission current evolved over three periods, the incubation, the fast increase, and the saturation periods. Ball-shaped diamond particles, faceted diamond crystals, and diamond films with well-faceted crystals were formed in the three periods. The current from a diamond-seeded substrate started to increase immediately without an incubation period, confirming that the current is from the diamond. Therefore, the current could be used for real-time monitoring of the diamond nucleation and growth.

Keywords: PACS; 81.05.Uw; 81.15.Gh; 81.20.KaDiamond films; Combustion-flame deposition; Negative bias; Thermionic emission; Real-time monitoring

Surface modification of 30CrNiMo8 low-alloy steel by active screen setup and conventional plasma nitriding methods by Sh. Ahangarani; A.R. Sabour; F. Mahboubi (pp. 1427-1435).

In this paper, we report on a comparative study of active screen plasma nitriding (ASPN) and conventional dc plasma nitriding (CPN) behavior of 30CrNiMo8 low-alloy steel that has been examined under various process conditions. The process variables included active screen setup parameters (screen and iron plate top lids placed on the screen setup with 8mm of hole size), treatment temperature (550 and 580°C), gas mixture (75/25 and 25/75 of N₂/H₂) and treatment time (5 and 10h) in 500Pa pressure. The structure and phases composition of the diffusion zone and compound layer were studied by X-ray diffraction (XRD), microhardness tests, light optical microscopy and scanning electron microscopy (SEM). It was observed that treated sample surfaces in both CPN and ASPN methods consist of γ′ and ɛ phases, and while the nitriding time and/or temperature increases, the intensity of ɛ phase in the compound layer will increase for ASPN and decrease for CPN method. Results show that the amount of nitrogen transferred from holes of screen toward the sample surface via sputtering and re-condensation mechanism can be affected due to the hardness and thickness of the layer.

Keywords: Plasma nitriding; Low-alloy steel; Active screen

In situ HCl etching of Si for the elaboration of locally misorientated surfaces by V. Destefanis; Y. Morand; J.M. Hartmann; D. Rouchon; J.C. Barbé; M. Mermoux (pp. 1436-1443).

We have studied the in situ HCl etching of Si active areas on patterned wafers. After some in situ HCl etching at 20Torr of Si(100), we have locally obtained 2μm long areas with misorientation angles around 4.5° towards 〈110〉. Furthermore, we have evidenced a recess shape transition from convex ( T≤865°C) to concave ( T≥895°C) as the etch temperature increases, with a nearly flat surface with no facets at T=880°C. The morphology of the etched structures at a given time, temperature andPHCl/PH2 ratio will be a function of the slope lengths and the pattern dimensions. Different kinds of surfaces (rounded areas, facets) were obtained in 3.5μm×3.5μm Si windows after HCl etching at 850°C during 300s, depending on the stress within. Thermal oxidations can indeed be used to increase by 65MPa up to 110MPa the compressive stress in those Si windows which are bordered by SiO₂ shallow trench isolation. An increase of the misorientation angle from 4.5° up to 6° occurred after the above-mentioned HCl etch when switching from conventional to highly strained Si windows. For the shortest etching times studied here (150s), a selective etching of 3.5μm×3.5μm Si windows edges is responsible for the misorientation. The etch is then more uniform. Stress gradients might consequently be one of the main misorientation causes. We have also probed the influence of the shallow trench isolation (STI) thickness on the misorientation. A morphological difference before HCl etching has been shown to be responsible for the transition from sloped to rounded areas. A local loading effect may prevail in this case.

Keywords: PACS; 81.15.Gh; 81.65.Cf; 68.55.JkLocalized misorientation; HCl etching; Silicon; III–V semiconductors; Facets

Particle saltation removal in laser-induced plasma shockwave cleaning by Ping Zhang; Bao-Min Bian; Zhen-Hua Li (pp. 1444-1449).

A new particle saltation removal model in laser-induced plasma shockwave cleaning is presented due to the drawbacks in other particle removal models. Considering the elastic energy stored in the adhered particle during shockwave–particle interaction, the threshold of the particle elastic deformation height, leading to the particle removal, is obtained. With taking the collision between gas molecules in plasma shockwave rear and adhered particle into account, the threshold of the plasma shockwave Mach number is also obtained which is a requirement to the shockwave strength. It is found that the smaller particle needs stronger shockwave than the larger particle. The gas pressure distribution characteristics in the plasma shockwave rear offer a saltation surrounding to the particle, and it is another requirement to the shockwave strength for a successful particle saltation. Finally, particle-cleaning experiment using laser-induced plasma shockwave proves the correctness of the particle saltation model.

Keywords: Laser-induced plasma; Particle removal; Mach number; Shockwave cleaning

Surface electroluminescence phenomena correlated with trapping parameters of insulating polymers by Guan-Jun Zhang; Kai Yang; Ming Dong; Wen-Bin Zhao; Zhang Yan (pp. 1450-1455).

Electroluminescence (EL) phenomena are closely linked to the space charge and degradation in insulating polymers, and dominated by the luminescence and trap centers. EL emission has been promising in defining the onset of electrical aging and in the investigation of dissipation mechanisms. Generally, polymeric degradation reveals the increment of the density of luminescence and trap centers, so a fundamental study is proposed to correlate the EL emission of insulating polymers and their trapping parameters. A sensitive photon counting system is constructed to detect the weak EL. The time- and phase-resolved EL characteristics from different polymers (LDPE, PP and PTFE) are investigated with a planar electrode configuration under stepped ac voltage in vacuum. In succession, each sample is charged with exposing to multi-needle corona discharge, and then its surface potential decay is continuously recorded at a constant temperature. Based on the isothermal relaxation current theory, the energy level and density of both electron and hole trap distribution in the surface layer of each polymer is obtained. It is preliminarily concluded that EL phenomena are strongly affected by the trap properties, and for different polymers, its EL intensity is in direct contrast to its surface trap density, and this can be qualitatively explained by the trapping and detrapping sequence of charge carriers in trap centers with different energy level.

Keywords: Insulating polymer; Electroluminescence; Trapping parameter; Surface potential decay; Isothermal relaxation current

The interface structure of nano-SiO₂/PA66 composites and its influence on material's mechanical and thermal properties by Xiangmin Xu; Binjie Li; Huimin Lu; Zhijun Zhang; Honggang Wang (pp. 1456-1462).

The PA66-based nanocomposites containing surface-modified nano-SiO₂ were prepared by melt compounding. The interface structure formed in composite system was investigated by thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The influence of interface structure on material's mechanical and thermal properties was also studied. The results indicated that the PA66 chains were attached to the surface of modified-silica nanoparticles by chemical bonding and physical absorption mode, accompanying the formation of the composites network structure. With the addition of modified silica, the strength and stiffness of composites were all reinforced: the observed increase depended on the formation of the interface structure based on hydrogen bonding and covalent bonding. Furthermore, the differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) showed that the presence of modified silica could affect the crystallization behavior of the PA66 matrix and lead to glass transition temperature of composites a shift to higher temperature.

Keywords: Interface structure; Nano-SiO; ₂; Thermal properties; Mechanical properties

Structural characterization and properties of lanthanum film as chromate replacement for tinplate by Xingqiao Huang; Ning Li (pp. 1463-1470).

Sulfide-stain resistance of La-passivated, unpassivated and Cr-passivated tinplate was measured using a cysteine tarnish test. Corrosion behavior of these tinplates was investigated using electrochemical impedance spectroscopy (EIS) measurement. The morphology, composition and thickness of lanthanum film were studied by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence spectrometry (XRF), respectively. La-passivation treatment remarkably enhances sulfide-stain resistance of tinplate, and sulfide-stain resistance of La-passivated tinplate is slightly higher than that of Cr-passivated tinplate. La-passivation treatment also significantly improves corrosion protection property of tinplate. In contact with 3.5% NaCl solution, corrosion resistance of La-passivated tinplate is close to that of Cr-passivated tinplate, and in contact with 0.1M citric-citrate buffer solution, corrosion resistance of La-passivated tinplate is higher than that of Cr-passivated tinplate. Lanthanum film is composed of spherical particles about 50–1000nm in diameter, while most part of tinplate's surface is covered with the small particles about 50–200nm. The film mainly consists of lanthanum and oxygen, which mainly exist as La₂O₃ and its hydrates such as La(OH)₃ and LaOOH. The amount of lanthanum in the film is about 0.0409g/m².

Keywords: PACS; 81.65.Rv; 81.65.Kn; 82.45.Bb; 81.15.PqTinplate; La-passivation; Sulfide-stain resistance; Corrosion behavior; Structural characterization

Scaling properties of fracture surfaces on glass strengthened by ionic exchange by F.J. Garza-Méndez; M. Hinojosa-Rivera; I. Gómez; E.M. Sánchez (pp. 1471-1474).

In this work the results of the statistical topometric analysis of fracture surfaces of soda-lime-silica glass with and without ionic exchange treatment are reported. In this case, the mechanism of substitution is K⁺–Na⁺. atomic force microscopy (AFM) was employed to record the topometric data from the fracture surface. The roughness exponent ( ζ) and the correlation length ( ξ) were calculated by the variable bandwidth method. The analysis for both glasses (subjected and non-subjected to ionic exchange) for ζ shows a value ∼0.8, this value agrees well with that reported in the literature for rapid crack propagation in a variety of materials. The correlation length shows different values for each condition. These results, along with those of microhardness indentations suggest that the self-affine correlation length is influenced by the complex interactions of the stress field of microcracks with that resulting from the collective behavior of the point defects introduced by the strengthening mechanism of ionic exchange.

Keywords: Ion exchange; Atomic force microscopy; Scaling factor; Soda lime silica glass; Surface enhancement

Anharmonic effects on B2–FeAl(110) surface: A molecular dynamics study by Jianfeng Tang; Wangyu Hu; Jianyu Yang; Yurong Wu (pp. 1475-1481).

Using molecular dynamics simulations and the analytic embedded-atom method (AEAM), the surface anharmonicity of B2–FeAl(110) has been studied in the temperature range from 0K to 1400K. The temperature dependence of the interlayer spacing, mean square vibrational amplitudes, surface phonon frequencies and line-widths, and layer structure factor have been calculated. The obtained results indicate that the anharmonic effects are small in the temperature range from 0K to 900K. The temperature dependences of the interlayer spacing indicates that the rippling effect of the B2–FeAl(110) surface is exhibited by the contraction of Fe surface atoms and the expansion of Al atoms, which persists at high temperatures. The temperature dependence of the layer structure factors shows that the B2–FeAl(110) surface does not disorder until the temperature of 1300K.

Keywords: PACS; 61.66.Dk; 68.35.Ja; 31.15.Qg; 68.60.DvB2–FeAl(1; 1; 0); Molecular dynamics; AEAM; Surface anharmonicity

Microstructure, microhardness and dry friction behavior of cold-sprayed tin bronze coatings by Xueping Guo; Ga Zhang; Wen-Ya Li; Lucas Dembinski; Yang Gao; Hanlin Liao; Christian Coddet (pp. 1482-1488).

In this paper, two types of tin bronze coatings (Cu–6wt.% Sn and Cu–8wt.% Sn) were prepared by cold spray process. The as-sprayed coatings were subjected to a vacuum heat treatment at 600°C for 3h. The coating microstructure, microhardness and tribological performance were characterized. The effects of the tin content and the vacuum heat treatment on the microstructure, microhardness and tribological behavior of the coatings were investigated. It is found that the as-sprayed CuSn6 (As6) and CuSn8 (As8) coatings exhibit practically an identical porosity. Meanwhile, As8 presents a higher microhardness than As6. In addition, the increase of the tin content in the powder feedstock leads to a lower wear rate. After a heat treatment, coating porosities are significantly reduced. However, the coating hardness is significantly decreased and the coating presents a much decreased wear resistance. For the as-sprayed coatings, such factors as ploughing and particle delamination could determine the sliding process. The heat treatment results in a distinct modification of the tribological behavior. For the annealed coatings, the adhesion, between the coating and the counterpart, could play a dominant role in the sliding process.

Keywords: Cold spray; Tin bronze; Heat treatment; Microstructure; Microhardness; Dry sliding wear

Generalized stacking fault energy in FCC metals with MEAM by Xiu-Mei Wei; Jian-Min Zhang; Ke-Wei Xu (pp. 1489-1492).

The second nearest-neighbor modified embedded atom method (2NN-MEAM) is used to investigate the generalized stacking fault (GSF) energy surfaces of eight FCC metals Cu, Ag, Au, Ni, Pd, Pt, Al and Pb. An offset is observed in all the metals for the displacement δ_us of unstable stacking fault energy from the geometrically symmetric displacement pointδus0. The offset value is the greatest for Al and the smallest for Ag. By analyzing the stable stacking fault energy γ_sf and unstable stacking fault energy γ_usf, it can be predicted that stacking fault is more favorable in Cu, Ag, Au, and especially in Pd than the other metals, while it is most preferred to create partial dislocation for Ag and to create full dislocation for Al.

Keywords: PACS; 61.43.Bn; 61.72.Mm; 98.38.BnStacking fault energy; MEAM; Slide

Effects of co-substitution on the electrical properties of BiFeO₃ thin films prepared by chemical solution deposition by Seung U. Lee; Sang Su Kim; Mun Heum Park; Jin Won Kim; Hyeun Kyung Jo; Won-Jeong Kim (pp. 1493-1497).

Ferroelectric BiFeO₃ thin films with Nd–Cr (or Sm–Cr) co-substitution (denoted by BNdFCr and BSmFCr, respectively) were deposited on the Pt(200)/TiO₂/SiO₂/Si(100) substrates by a chemical solution deposition method. X-ray diffraction patterns revealed the formation of BNdFCr and BSmFCr thin films without any secondary phases. The co-substituted BNdFCr (or BSmFCr) thin films, which were annealed at 550°C for 30min in N₂ atmosphere, exhibited enhanced electrical properties compared to BFO thin films with the remanent polarization (2 P_r) and coercive electric field (2 E_c) of 196, 188μC/cm² and 600, 570kV/cm with the electric field of 800kV/cm, respectively. The leakage current densities of BNdFCr and BSmFCr thin films measured at room temperature were approximately three orders of magnitude lower than that of BFO thin film, and the leakage current at room temperature of the thin films exhibited three distinctive conduction behaviors. Furthermore, the values of pulse polarizations [i.e., +( P*– P^{^}) or −( P*– P^{^})] of BNdFCr and BSmFCr thin films were reasonably unchanged up to 1.4×10¹⁰ switching cycles.

Keywords: BiFeO; ₃; thin films; Chemical solution deposition; Electrical properties

New perspectives about molecular arrangement of primary and permanent dentin by Ana Flávia Sanches Borges; Renata Andrade Bitar; Kamila Rosamilia Kantovitz; Américo Bortollazo Correr; Airton Abrahão Martin; Regina Maria Puppin-Rontani (pp. 1498-1505).

The dentin quality of primary and permanent teeth was inspected by Fourier transformed Raman spectroscopy (FT-Raman); scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and hardness test. Middle dentin of crowns were reached by carbide bur abrading providing a uniform smear layer. Phosphoric acid was applied in order to simulate the etching of total etching adhesive systems. The groups were ( n=10): G1 (primary dentin smear layer); G2 (35% phosphoric acid etched primary dentin); G3 (permanent dentin smear layer); G4 (35% phosphoric acid etched permanent dentin). FT-Raman results were subjected to cluster analysis. SEM/EDS were made in order to add the data obtained by FT-Raman. The hardness data were subjected to ANOVA and Tukey test. FT-Raman showed differences among groups, either to organic or inorganic content. For the organic content, primary and permanent dentin became similar after the etching; conversely, the inorganic content showed differences for the two substrates. Hardness test showed no significant differences between primary and permanent dentin, before or after etching, but the etching decreased these values. The mineral content arrangement of primary dentin is different from permanent dentin, independently of the etching. The substrate type did no influence the hardness, but the etching decreased it.

Keywords: PACS; 47.11.Kb; 47.11.MnDentin; Mineral content; FT-Raman; Hardness

Stability test and EXAFS characterization of plasma prepared Pd/HZSM-5 catalyst for methane combustion by Dangguo Cheng; Kazu Okumura; Yongbing Xie; Chang-jun Liu (pp. 1506-1510).

Pd/HZSM-5 catalysts prepared via glow discharge plasma reduction followed by calcination thermally show excellent enhanced stability for methane combustion. EXAFS characterization confirms that argon glow discharge reduces Pd/HZSM-5 catalyst effectively at close to room temperature. After thermal calcination of argon plasma reduced Pd/HZSM-5 catalyst under air, specific tetragonal PdO species are formed. This kind of active PdO species keeps stable during methane combustion, which leads to the observed excellent stability of plasma prepared Pd/HZSM-5 catalyst. EXAFS characterization also shows argon plasma reduction can help to remove Cl, which has a negative effect on catalysts properties.

Keywords: PACS; 82.65.−s; 52.77.−jMethane combustion; Pd/HZSM-5; Stability; Glow discharge; Plasma; EXAFS

Features of microarc oxidation coatings formation technology in slurry electrolytes by V.N. Malyshev; K.M. Zorin (pp. 1511-1516).

A group of electrolytes composed of different powders entered into electrolyte presents a separate direction in microarc oxidation (MAO) technology. This group of electrolytes is most complex and however it has not been sufficiently studied yet. This paper shows that addition of powders of different nature into electrolyte influences both on properties of obtained coatings and on speed of their formation. The MAO-coatings formed in similar electrolytes-suspensions or slurry electrolytes (SE) contain in their composition an essential share of powder material entered into electrolyte as corpuscles of disperse phase (DP). Different nonmetallic combinations are used: oxides, carbides, borides, nitrides of metals and others. The particular conditions of microarc discharge regime (high temperature and pressure in a zone of breakdown) cause a thermolysis of electrolyte together with weighed corpuscles of solid matter, the realization of plasma chemical reactions on oxidizing surface and provide the synthesis of chemical combinations in an oxide matrix. A new composition of slurry electrolyte which allows improving the quality of obtained coatings on the basis of held investigations was developed.

Keywords: JEL classification; 81.65Mq; 82.33Xj; 82.45Xy; 82.70−y; 82.70KjMicroarc oxidation; Slurry electrolytes; Oxides; Borides; Carbides; Nitrides of metals; Ceramic coating; Disperse phase

Modeling the effects of oxidizer, complexing agent and inhibitor on material removal for copper chemical mechanical polishing by Yongguang Wang; Yongwu Zhao (pp. 1517-1523).

The paper presents a novel mathematical model that systematically describes the role of oxidizer, complexing agent and inhibitor on the material removal in chemical mechanical polishing (CMP) of copper. The physical basis of the model is the steady-state oxidation reaction and etched removal in additional to mechanical removal. It is shown that the complexing agent concentration–removal relation follows a trend similar to that observed from the effects of oxidizer on Cu removal in CMP. In addition, the removal rate and the coupled effects of the chemical additives are determined from a close-form equation, making use of the concepts of chemical–mechanical equilibrium and chemical kinetics. The model prediction trends show qualitatively good agreement with the published experimental data. The governing equation of copper removal reveals some insights into the polishing process in addition to its underlying theoretical foundation.

Keywords: Chemical mechanical polishing; Chemical kinetics; Copper; Complexing agent; Inhibitor

ITO/Au/ITO multilayer thin films for transparent conducting electrode applications by Y.S. Kim; J.H. Park; D.H. Choi; H.S. Jang; J.H. Lee; H.J. Park; J.I. Choi; D.H. Ju; J.Y. Lee; Daeil Kim (pp. 1524-1527).

Transparent and conducting ITO/Au/ITO multilayered films were deposited without intentional substrate heating on polycarbonate (PC) substrate using a magnetron sputtering process. The thickness of ITO, Au and ITO metal films in the multilayered structure was constant at 50, 10 and 40nm, respectively.Although the substrate temperature was kept constant at 70°C, ITO/Au/ITO films were polycrystalline with an (110) X-ray diffraction peak, while single ITO films were amorphous. Surface roughness analysis indicated ITO films had a higher average roughness of 1.76nm, than the ITO/Au/ITO film roughness of 0.51nm. The optoelectrical properties of the ITO/Au/ITO films were dependent on the Au thin film, which affected the ITO film crystallinity. ITO/Au/ITO films on PC substrates were developed with a resistivity as low as 5.6×10⁻⁵Ωcm and a high optical transmittance of 71.7%.

Keywords: Indium tin oxide; Gold; Resistivity; Optical property; XRD; AFM

Adsorption and film growth of N-methylamino substituted triazoles on copper surfaces in hydrocarbon media by Martina Levin; Per Wiklund; Hans Arwin (pp. 1528-1533).

The adsorption of benzotriazole (BTA), tolyltriazole (TTA) and two different N-methylaminosubstituted triazoles on copper surfaces in hydrocarbon media has been examined by in situ ellipsometry and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). All four triazoles were found to form films and from the ellipsometric study were the film thicknesses estimated to be in the range of 0.5–2nm after 1000min exposure time. The layers formed from BTA and TTA were thicker (up to 2nm) than the layers from N-aminomethyl substituted triazoles (roughly 0.5nm). Desorption was studied qualitatively and 20% or less of the adsorbed material were found to desorb. The ToF-SIMS study showed that while BTA and TTA adsorbed intact did the N-aminomethyl substituted triazoles appear to loose their aminomethyl tails on binding since only signals corresponding to triazole moieties of the compounds were detected.

Keywords: PACS; 81.65.Kn; 82.45.BbCu; Triazole; Inhibitor; Ellipsometry; ToF-SIMS

Tracer studies of anodic films formed on aluminium in malonic and oxalic acids by S.J. Garcia-Vergara; P. Skeldon; G.E. Thompson; H. Habakaki (pp. 1534-1542).

Using a tungsten-containing layer, incorporated into sputtering-deposited aluminium, as a tracer, the growth of porous anodic films in malonic and oxalic acid electrolytes has been investigated using transmission electron microscopy, Rutherford backscattering spectroscopy and nuclear reaction analysis. Comparisons were also made with films formed in phosphoric acid electrolyte, which have been studied previously. The findings reveal a distortion of the tracer layer within the barrier region of the porous films, evident as a lagging of the tracer beneath the pores relative to that in the adjacent cell wall region. Further, the films are significantly thicker than the layer of metal consumed during anodizing and display smooth-sided pores. The anodizing behaviours are consistent with a major role for field-assisted flow of film material within the barrier layer in the development of the pores.

Keywords: Aluminium; Anodizing; Anodic films; Malonic acid; Oxalic acid

Erratum to “New concept to remove heavy metals from liquid waste based on electrochemical pH-switchable immobilized ligands” [Appl. Surf. Sci. 253 (2007) 3263–3269] by P. Viel; L. Dubois; J. Lyskawa; M. Sallé; S. Palacin (pp. 1543-1543).

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Applied Surface Science (v.254, #5)