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Applied Surface Science (v.249, #1-4)
A novel emulsion route to sub-micrometer polyaniline/nano-ZnO composite fibers by Yongjun He (pp. 1-6).
With a average diameter of 700–900nm and a length of 20–35μm, sub-micrometer fibers of polyaniline/nano-ZnO composites (PANI/nm-ZnO) were synthesized in a toluene/water emulsion stabilized by ZnO nanoparticles. It was found that the morphology of the resulting PANI/nm-ZnO composites depended on the volume ratio of toluene to water ( R) in the reaction mixture. When R was in the range of 0.03–0.07, stable Pickering emulsion was formed and the oxidative polymerization of aniline was confined at the toluene/water interface, generating sub-micrometer PANI/nm-ZnO fibers. When R=0.11 and 0.01, the composites with dendritic and polyhedral morphology, respectively, were formed. TEM, XRD, FTIR and TGA etc. were used to characterize the sub-micrometer fibers. It was found that the structure of PANI in the composite fibers was identical to that of the amorphous emeraldine form. The sub-micrometer fibers showed hydrophilic features and their conductivity was higher than that of the PANI/nm-ZnO composites with dendritic or polyhedral morphology.
Keywords: PACS; 81.05YsPolyaniline; ZnO nanoparticles; Composites; Sub-micrometer fibers; Pickering emulsion
Replacement of adsorbed alkanethiolate on Au with carboxyl-terminated thiol in solution: effect of alkyl chain length by Yong-Kwan Kim; Jae Pil Koo; Jeong Sook Ha (pp. 7-11).
We have investigated the effect of the alkyl chain length on the replacement of the self-assembled alkanethiolate on Au surface with carboxyl-terminated thiol dissolved in solution. Immersion time-dependent replacement of self-assembled alkanethiolates on Au substrate was monitored by lateral force microscope (LFM), contact angle measurement, and infrared spectroscopy (IRS). Both the self-assembled monolayers (SAM) of 1-octadecanethiol (ODT) and octanethiol (OT) were reacted with carboxyl-terminated 11-mercaptoundecanoic acid (MUA) molecules in ethanol. OT SAM was rapidly replaced by MUA molecules. More than 50% of OT molecules were replaced by MUA within the initial 50h. In contrast, less than 10% of ODT molecules were replaced by MUA within the same time scale. This can be explained in terms of the relative stability between methyl- and carboxyl-terminated thiolates on Au surface, depending upon the chain length and the lateral hydrogen bonding.
Keywords: PACS; 82.65 MySelf-assembled monolayer; Stability of SAM; Replacement; Lateral force microscope; μ-Contact printing
Enhanced peak separation in XPS with external biasing by Gulay Ertas; U. Korcan Demirok; Sefik Suzer (pp. 12-15).
We have demonstrated that the Au 4f peaks of the capped gold nanoparticles deposited on a SiO2 (20nm)/Si substrate can be separated form the Au 4f peaks of a gold metal strip, in contact with the same sample, by application of an external voltage bias to the sample rod while recording the XPS spectra. The external bias controls the flow of low-energy electrons falling on to the sample which in-turn controls the extent of the differential charging of the oxide layer leading to shifts in the binding energy of the gold nanoparticles in contact with the layer. The method is simple and effective for enhancing peak separation and identification of hetero-structures.
Keywords: External biasing; Differential charging; Peak separation; Gold nanoclusters
Interfacial conditions and electrical properties of the SrBi2Ta2O9/ZrO2/Si (MFIS) structure according to the heat treatment of the ZrO2 buffer layer by Chul-Ho Park; Jae-Hyun Kim; Min-Cheol Kim; Young-Gook Son; Mi-Sook Won (pp. 16-22).
The possibility of the ZrO2 buffer layer as the insulator for the metal–ferroelectric–insulator–semiconductor (MFIS) structure was investigated. ZrO2 and SrBi2Ta2O9 (SBT) thin films were deposited on the p-type Si(111) wafer by the rf magnetron-sputtering method. According to the process with and without the post-annealing of the ZrO2 buffer layer, the diffusion amount of Sr, Bi, Ta elements show slight difference through the glow discharge spectrometer (GDS) analysis. From X-ray photoelectron spectroscopy (XPS) results, we could confirm that the post-annealing process affects the chemical binding condition of the interface between the ZrO2 thin film and the Si substrate, which results in the chemical stability of the ZrO2 thin film. The electrical properties of the MFIS structure were relatively improved by the post-annealing ZrO2 buffer layer. The window memory of the Pt/SBT (260nm, 800°C)/ZrO2 (20nm) structure increases from 0.75 to 2.2V. This memory window is sufficient for the practical application of the NDRO-FRAM operating at low voltage.
Keywords: FRAM; Buffer layer; SrBi; 2; Ta; 2; O; 9; MFIS structure
Influence of the morphology of ferroelectric SrBi2Ta2O9 thin films deposited by metal organic decomposition on its electrical characteristics by M. Moert; G. Schindler; T. Mikolajick; N. Nagel; W. Hartner; C. Dehm; H. Kohlstedt; R. Waser (pp. 23-30).
The morphologies of SrBi2Ta2O9 (SBT) thin films deposited by metal organic decomposition and crystallized at temperatures between 600 and 800°C for 45min are studied by atomic force microscopy (AFM) and X-ray diffractometry (XRD). From these analytical investigations a detailed quantitative description of the phase transformation from the non-ferroelectric fluorite to ferroelectric Aurivillius phase including changes in the microstructure and surface roughness are extracted. These results are correlated to electrical characteristics from hysteresis loop and leakage current measurements of corresponding Pt/SBT/Pt capacitor modules. As a result, increased values of remnant polarization can directly be correlated to the Aurivillius surface coverage. It is shown that the measured leakage currents are dominantly influenced by the grain boundaries and, therefore, are very sensitive on the overall film granularity. The SBT roughness is not predominant for the leakage currents, but is very critical for capacitor shorting. Potentially, the results provided with this work provide instruments for design of electrical characteristics, to meet desired FeRAM specifications.
Keywords: PACS; 77.84.Dy; 81.10.AjFerroelectric; SBT; Morphology; Hysteresis; Leakage current; Phase transformation
Role of Pb for Ag growth on H-passivated Si(1 0 0) surfaces by S. Mathew; B. Satpati; B. Joseph; B.N. Dev (pp. 31-37).
We have deposited Ag on hydrogen passivated Si(1 0 0) surfaces under high vacuum conditions at room temperature. The deposition, followed by annealing at 250°C for 30 min, produced silver islands of an average lateral size36±14 nm. Depositing a small amount of Pb prior to Ag deposition reduced the average island size to14±5 nm. A small amount of Pb, initially present at the Ag–Si interface, is found to be segregating to the surface of Ag after annealing. Both these aspects, namely, reduction of the island size and Pb floating on the Ag surface conform to the surfactant action of Pb. Samples have been characterized by transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy (RBS). A selective etching process that preferentially removes Pb, in conjunction with RBS, was used to detect surface segregation of Pb involving depth scales below the resolution of conventional RBS. The annealing and etching process leaves only smaller Ag islands on the surface with complete removal of Pb. Ag growth in the presence of Pb leads to smaller Ag islands with a narrower size distribution.
Keywords: PACS; 78.67.Bf; 82.70.Uv; 82.80.Yc; 81.65.RvAg nanoislands on Si; Surfactant effect in island size reduction; Transmission electron microscopy (TEM); Rutherford backscattering spectrometry (RBS); Hydrogen passivation
Imaging low-dimensional magnetism with slow electrons by R. Zdyb; A. Pavlovska; A. Locatelli; S. Heun; S. Cherifi; R. Belkhou; E. Bauer (pp. 38-44).
Two aspects of low-dimensional magnetism are discussed: the spin-dependent quantization effects in perfect two-dimensional single crystal layers and the magnetic domain structure of submicron magnetic patterns. Both require high lateral resolution and surface sensitivity. This is provided by spin-polarized low energy electron microscopy (SPLEEM) and X-ray magnetic circular dichroism photoemission electron microscopy (XMCDPEEM).
Keywords: Low-dimensional magnetism; Spin-polarized low energy electron microscopy; X-ray magnetic circular dichroism photoemission electron microscopy
Excimer laser modification of thin AlN films by D.G. Georgiev; L.W. Rosenberger; Y.V. Danylyuk; R.J. Baird; G. Newaz; G. Shreve; G. Auner (pp. 45-53).
The potential of excimer laser micro-processing for surface modification of aluminum nitride (AlN) thin films was studied. Thin films of AlN were deposited by plasma-source molecular beam epitaxy (PSMBE) on silicon and sapphire substrates. These films were then exposed to different fluence levels of KrF ( λ=248nm) excimer laser radiation in an ambient air environment, and the changes in the film surface were studied by X-ray photoelectron spectroscopy, atomic force microscopy and optical spectrophotometry. The results show that there is a narrow range of laser fluences, just above 1.0J/cm2, within which mostly photochemical transformations of the film surface take place. These transformations consist of both oxidation and decomposition to metallic Al of the original film within a very thin sub-surface layer with thickness of several tens of nanometers. No changes were observed at fluences below 1.0J/cm2. Above a fluence of 1.0J/cm2, severe photomechanical damage consisting of film cracking and detachment was found to accompany the photochemical and photothermal changes in the film.
Keywords: Excimer laser; Plasma-source molecular beam epitaxy; Aluminum nitride
Evaluation of the diffusion coefficient of nitrogen in Fe4N1− x nitride layers during microwave post-discharge nitriding by I. Campos; R. Torres; O. Bautista; G. Ramírez; L. Zuñiga (pp. 54-59).
The evaluation of the growth kinetics of Fe4N1− x (γ′) phase under microwave post-discharge nitriding in ARMCO iron has been carried out through this project. A mathematical model that considers the iron nitride growth is proposed in a non-saturated nitrogen medium with a finite length of 2 L, where the interface concentrations remain constant during the treatment. Growth kinetics of γ′, during microwave post-discharge nitriding process, is rapid in short times of treatment, due to the presence of neutral and ionized species, which produce a rapid evolution of nitrogen concentration on the substrate surface. Concentration on the surface is controlled by the parameters of the process for γ′ nitride formation. Experimental results achieved during the process are compared to the mathematical model forecast, along with the results presented by other authors.
Keywords: Nitriding; Diffusion coefficient; Nitride layer; Post-discharge; Growth kinetics
Transparent oxygen impermeable AlO x thin films on polycarbonate deposited by reactive ion beam sputtering by Jin-Wook Seong; Sang-Mun Kim; Daiwon Choi; K.H. Yoon (pp. 60-64).
The AlO x thin films were deposited on the polycarbonate by reactive ion beam sputtering (RIBS) at different oxygen partial pressures where the AlO x thin film with O/Al ratio of 1.5 was formed when oxygen partial pressure increased from 4×10−5 to 2×10−4Torr. As a result, oxygen transmission rate (OTR) of the barrier significantly decreased from 24cm3/m2 day to around 2cm3/m2 day with increase in oxygen partial pressure. Optical transmittances of the films were in the 86–88% range at 550nm versus 89% for the pure polycarbonate film.
Keywords: AlO; x; thin films; Oxygen partial pressure; Reactive ion beam sputtering (RIBS); Stoichiometric ratio; Oxygen transmission rate (OTR)
Dopant effect on in situ doped metal-induced lateral crystallization of amorphous silicon films by Jun-Dar Hwang; Jyh-Yeu Chang; Ching-Yuan Wu (pp. 65-70).
Dopant (boron or phosphorus) effect on metal-induced lateral crystallization (MILC) of amorphous silicon (a-Si) films has been systematically studied by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The MILC was realized by depositing a-Si film onto an oxidized Si wafer and then annealing in a N2 atmosphere. The doped amorphous films have been developed by plasma-enhanced chemical vapor deposition (PECVD). Various dopant gases and annealing times were investigated to study dopant effects on MILC films. It has been found that the un-doped poly-Si film has a MILC length larger than that of samples doped with boron or phosphorus. The phosphorus-doped films exhibit larger grain size as compared with un-doped and boron-doped films. Larger MILC length is obtained by increasing annealing time, but the MILC rate is decreased. In addition, nickel-silicides were found in the doped samples by XRD. Physical mechanisms for these experimental results are proposed.
Keywords: MILC; Polycrystalline silicon; PECVD; Nickel-silicide
Hydrothermal growth of perpendicularly oriented ZnO nanorod array film and its photoelectrochemical properties by Min Guo; Peng Diao; Shengmin Cai (pp. 71-75).
By using a low cost, low-temperature hydrothermal approach, well-aligned ZnO nanorods with high aspect ratio have been successfully prepared on ITO substrates that were pre-modified with ZnO nanoparticles. The obtained ZnO nanostructure was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. The results of characterization indicate that the nanorods are high-quality single crystals, grow along [001] direction and for 2h growth time 90% of them have diameters of 120–190nm. The thin films consisting of ZnO nanorods with controlled orientation onto ITO substrates allow a more efficient transport and collection of photogenerated electrons through a designed path. For a sandwich-type cell, with 0.3mol/L LiI and 0.03mol/L I2 in propylene carbonate electrolyte, the overall solar energy conversion efficiency reaches 2.1%.
Keywords: Zinc oxide; Nanorod arrays; Hydrothermal method; Photoelectrochemistry
Hydrophilic modification of poly(ether sulfone) ultrafiltration membrane surface by self-assembly of TiO2 nanoparticles by Ming-Liang Luo; Jian-Qing Zhao; Wu Tang; Chun-Sheng Pu (pp. 76-84).
Membrane fouling is one of the major obstacles for reaching the ultimate goal, which realizes high flux over a prolonged period of ultrafiltration (UF) operation. In this paper, TiO2 nanoparticles of a quantum size (40nm or less) in anatase crystal structure were prepared from the controlled hydrolysis of titanium tetraisopropoxide and characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The hydrophilic modification of poly(ether sulfone) UF membrane was performed by self-assembly of the hydroxyl group of TiO2 nanoparticle surface and the sulfone group and ether bond in poly(ether sulfone) structure through coordination and hydrogen bond interaction, which was ascertained by X-ray photoelectron spectroscopy (XPS). The morphology and hydrophilicity were characterized by scanning electron microscopy (SEM) and contact angle test, respectively. The composite UF membrane was also characterized in terms of separation behavior for polyethylene glycol-5000 solute. The experimental results show that the composite UF membrane has good separation performance and offers a strong potential for possible use as a new type of anti-fouling UF membrane.
Keywords: Ultrafiltration; Self-assembly; Anti-fouling membrane; TiO; 2; nanoparticles; Hydrophilicity
Simulation of growth process of thin film on non-planar substrate by H.J. Qi; J.D. Shao; D.P. Zhang; K. Yi; Z.X. Fan (pp. 85-90).
In (2+1) dimension, growth process of thin film on non-planar substrate in Kuramoto–Sivashinsky model is studied with numerical simulation approach. 15×15 semi-ellipsoids arranged orderly on the surface of substrate are used to represent initial rough surface. The results show that at the initial stage of growth process, the surface morphology of thin film appears to be grid-structure, and the interface width constantly decreases with the growth time, then reaches minimum. However, the grid-structure becomes ambiguous, and granules of different sizes distribute evenly on the surface of thin film with the increase of growth time. Thereafter, the average size of granules and the interface width gradually increase, and the surface morphology of thin film presents fractal properties. The numerical results of height–height correlation functions of thin film verify the surface morphology of thin film to be fractal for a longer growth time. By fitting of the height–height correlation functions of thin film with different growth times, the growth process is described quantitatively.
Keywords: PACS; 05.45.Pq; 68.55.Jk; 81.15.AaSimulation; Morphology; Growth model
A comparative study of the electrical characteristics of metal-semiconductor-metal (MSM) photodiodes based on GaN grown on silicon by Y.C. Lee; Z. Hassan; F.K. Yam; M.J. Abdullah; K. Ibrahim; M. Barmawi; Sugianto; M. Budiman; P. Arifin (pp. 91-96).
We report on the characteristics of metal-semiconductor-metal (MSM) photodiodes based on GaN films grown on silicon substrates by electron cyclotron resonance (ECR) plasma-assisted metalorganic chemical vapor deposition (PA-MOCVD) at growth temperature of 200 and 600°C. Structural analysis of the GaN samples used for the photodiodes fabrication were performed by using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX) to analyze the crystalline quality of the samples. The analysis has revealed that the GaN samples grown at 200 and 600°C were in amorphous and microcrystalline phase, respectively. Electrical characterization of the MSM photodiodes were carried out by using current–voltage ( I– V) measurements. At 10V, the photodiodes based on amorphous GaN has a dark current of 0.18μA while the microcrystalline GaN based photodiode has a dark current of 18μA.
Keywords: PACS; 61.10.−i; 61.43.Dq; 68.55.−a; 73.40.SxElectrical characterization; Crystalline structure; III–V nitrides; Photodiodes
Modeling of Fe growth on Mo(110) by Adrian Canzián; Hugo O. Mosca; Guillermo Bozzolo (pp. 97-109).
Atomistic modeling of Fe deposition of Mo growth using the BFS method for alloys describes the early stages of the formation of ultrathin Fe films on refractory metal substrates (Mo). Atom-by-atom analysis and Monte Carlo simulations are used to examine the composition of the islands with increasing Fe coverage. Experimentally known features for submonolayer coverage are successfully reproduced and explained. Beyond 1ML, simulation results suggest that the stability of the Fe interlayer might be compromised, leading to the formation of islands with mixed composition.
Keywords: Thin film growth; Computer simulations; Iron; Molybdenum; Semi-empirical methods and model calculations
Electron induced deposition and in situ etching of CrO xCl y films by S. Wang; Y.-M. Sun; J.M. White (pp. 110-114).
In a 3keV electron system, we have studied both electron beam induced CrO xCl y deposition using precursor CrO2Cl2 and electron beam induced etching of as-deposited CrO xCl y film using Cl2. The CrO2Cl2 pressure, 6.5×10−5Torr, was experimentally observed to be a threshold for CrO xCl y deposition. The Cr film is a composite of Cr, O and Cl with a ratio of Cr:O:Cl=1:2.2:1.1, and under electron beam irradiation, O increases while Cl decreases. As-deposited CrO xCl y films can be etched in situ by chlorine at a pressure of 6×10−4Torr with an electron flux of 10mAcm−2, demonstrating that Cl2 pressure is the key in initiating the etching reaction.
Keywords: CrO; x; Cl; y; films; Electron beam induced deposition (EBID); AES
Water adsorption on plasma sprayed transition metal oxides by Mika Harju; Tapio Mäntylä; Kalle Vähä-Heikkilä; Vesa-Pekka Lehto (pp. 115-126).
The aim of this study was to characterize water adsorption on plasma sprayed chromia and titania coatings. Both materials are widely used in industry as wear and corrosion resistant coatings. During plasma spraying both materials become oxygen deficient so that high concentrations of oxygen vacancies are formed.Vapor adsorption experiments were performed using microcalorimetry and isothermal gas adsorption experiments. Studies were performed to samples of two or three different degree of surface hydroxylation. The surface hydroxide content was controlled using heat treatments at 100, 200 or 400°C.All experiments were repeated to plasma sprayed coating samples, which were pre-heat-treated (12h at 1000°C). It was found that behavior of water adsorption is sensitive to both temperature of dehydroxylation and initial concentration of surface defects especially for TiO2 samples.
Keywords: PACS; Surface reactions: 82.65.J,Y; Adsorption–chemisorption: 82.65.Y; Plasma spraying: 81.15.RWater adsorption; Plasma spraying; Oxides
Evolution of near-surface concentration profiles of Cr during annealing of Fe–15Cr polycrystalline alloy by Eungyeul Park; Boris Hüning; Michael Spiegel (pp. 127-138).
For the development of surface modification of Fe–Cr alloys, the surface chemistry of Fe–15at.% Cr alloy specimen concerning the initial stage of oxidation and the effects of hydrogen during annealing and following oxidation was investigated. Samples were exposed to a heat-treatment atmosphere; annealing, oxidation and annealing followed by oxidation in air and N2–H2 gas mixtures at 800°C. After the heat treatments, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the morphology, elemental depth profiles and the chemical states of the elements.In the initial stage of oxidation, the chemistry of the oxide layer on the surface transformed as following sequence: Fe-rich oxide→duplex oxide layer (outer Fe-rich and inner Cr-rich)→Cr-rich mono-phase layer (M2O3). In the transformation, the reaction rate for the formation of Cr-rich oxide layer was controlled by the diffusion of cations. The annealing in H2-containing atmospheres increased the Cr content at the surface. The increase of hydrogen content in the atmosphere further increased the Cr to Fe ratio in near-surface, and the thickness of the layer affected by the heat treatment. The selective oxidation of chromium occurred as internal Cr2O3 formation, as a function of the Cr content, rather than the oxygen partial pressure. Hydrogen facilitated the diffusion of chromium probably by cleaning of fast diffusion paths. The addition of hydrogen in the annealing atmosphere prior to the oxidation was beneficial to obtain a Cr-rich oxide layer on the surface.
Keywords: PACS; 68.35.F (diffusion at solid surface and solid–solid interface); 81.65.M (oxidation (materials)); 64.75 (segregation); 82.65.J (surface reactions); 61.16.B (scanning electron-microscopy (SEM)); 79.60 (X-ray photoelectron spectroscopy)Fe–Cr alloy; XPS; Initial oxidation; Selective oxidation; Cr segregation
Nucleation and growth modes of ZnO deposited on 6H–SiC substrates by A.B.M.A. Ashrafi; Y. Segawa; K. Shin; J. Yoo; T. Yao (pp. 139-144).
ZnO nucleated initially with two-dimensional (2D) islands on 6H–SiC substrates. With the increase of ZnO layer thickness, however, the 2D islands led to coalescence and grain growths. The aspect ratios of these islands/coalescences/grains were found to be thickness dependence that has been interpreted by a schematic model. The growth mode transition from 2D islands to three-dimensional (3D) grains is the result of strain energy relaxation accumulated by lattice and thermal mismatches. An analog result diffracted in transmission electron microscopy with misfit dislocations that extended into the ZnO epilayers to be ≤150nm. The secondary ion-mass spectroscopy analysis exhibited anomalous impurities contributed by an interdiffusion in between ZnO and SiC materials.
Keywords: PACS; 81.05.Dz; 81.65.−b; 68.55.Jk; 71.55.−I; 68.55.LnNucleation; Growth modes of ZnO; Role of biaxial strain; Interface geometry
Control of carbon nanotube growth using cobalt nanoparticles as catalyst by Yoon Huh; Malcolm L.H. Green; Young Heon Kim; Jeong Yong Lee; Cheol Jin Lee (pp. 145-150).
We have controllably grown carbon nanotubes using uniformly distributed cobalt nanoparticles as catalyst. Cobalt nanoparticles with a uniform size were synthesized by chemical reaction and colloidal solutions including the cobalt nanoparticles were prepared. The cobalt nanoparticles were uniformly distributed on silicon substrates by a spin-coating method. Carbon nanotubes with a uniform diameter were synthesized on the cobalt nanoparticles by thermal chemical vapor deposition of acetylene gas. The density and vertical alignment of carbon nanotubes could be controlled by adjusting the density of cobalt (Co) nanoparticles.
Keywords: PACS; 81.05.Tp; 81.15.Gh; 61.46.+w; 81.20.KaCarbon nanotubes; Catalyst nanoparticles; Chemical vapor deposition; Growth control
Thick and macroporous anodic alumina membranes for self-lubricating surface composites by Hui Wang; Haowei Wang (pp. 151-156).
Aluminum-base self-lubricating surface composites require thick and macroporous alumina membranes to add lubricants easily. The thick anodic alunima films obtained in sulfuric acid and oxalic acid are always microporous, while the macroporous films in general phosphoric acid are very thin. In this paper, thick and macroporous alumina layers were fabricated successfully with a phosphate-base solution. The anodizing process in this compound solution and the effects on the thickness of the oxide films were investigated in detail. The results indicate that the growth of porous layers in this solution undergo three stages during anodizing, same with in the general solution. This electrolyte is sensitive to anodizing temperature which affects current density in great degree.The additive (including organic carboxylic acid and Ce salt) in the phosphate-base electrolyte plays an important role on the increase of film thickness. In this compound electrolyte, the pore diameter of the anodic alumina membranes is about 100nm in average, pore density is 18 pores μm−2 and porosity 14%. The thickness can exceed 20μm with appropriate anodizing time and temperature.
Keywords: Anodization; Surface composite; Self-lubrication; Aluminum
High-reflectance 193nm Al2O3/MgF2 mirrors by Shang Shuzhen; Shao Jianda; Liao Chunyan; Yi Kui; Fan Zhengxiu; Chen Lei (pp. 157-161).
Thin-film single layers of Al2O3 and MgF2 were deposited upon super polished fused-silica by electron-beam evaporation. The subsequent optical constants n and k were reported for the spectral range of 180–230nm. High-reflectance dense multilayer coatings for 193nm were designed on the basis of the evaluated optical constants and produced. The spectra of the reflectance of HR coatings were compared to the theoretical calculations. HR mirrors of 27 layers with a reflectance of more than 98% were reported.
Keywords: Optical coatings; 193; nm; HR mirrors; Al; 2; O; 3; MgF; 2
In situ and ex situ characterisation of the passive film on a ferritic stainless steel in molten sodium hydroxide by Javor Kolchakov; Tzvety Tzvetkoff; Martin Bojinov (pp. 162-175).
Voltammetric and electrochemical impedance spectroscopic measurements in combination with ex situ surface analysis are used to characterise the passive state of Fe–18% Cr in molten NaOH at 470°C. The areas of corrosion, passivity and transpassivity are derived from experimental voltammetric data and thermodynamic considerations. Impedance measurements in a wide potential range are performed to study the conductivity mechanism of the anodic layers formed. The surface composition of the passive film is estimated by X-ray photoelectron spectroscopy and its in-depth composition by Auger electron spectroscopy. A transfer function based on a tentative kinetic model is proposed to describe the impedance spectra. The parameters of the transfer function are determined by best-fit calculation and some of the kinetic and transport parameters characterising the film growth process are estimated.
Keywords: PACS; 81.65 (surface treatments); 82.45 (electrochemistry); 84.37 (impedance-electrical); 82.80.P (Auger spectroscopy); 79.60 (X-ray photoelectron spectra-surface analysis)Stainless steel; Molten hydroxide; Passive film; Electrochemical impedance spectroscopy; Surface analysis; Kinetic model
New telechelic compounds as corrosion inhibitors for steel in 1M HCl by M. Elayyachy; B. Hammouti; A. El Idrissi (pp. 176-182).
Two new telechelic compounds have been synthesised and tested as inhibitors for the corrosion of steel in 1M HCl solution. Weight loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods are used. The inhibiting action increases with the concentration of methyl 4-{2-[(2-hydroxyethyl)thio]ethyl}benzoate (T2) and 11-[(2-hydroxyethyl)thio]undecan-1-ol (T3) to attain 92% at 10−3M and 90% at 10−4M, respectively. Good agreement between gravimetric and electrochemical methods (potentiodynamic polarisation and EIS) was observed. Polarisation measurements show also that T2 and T3 act as mixed inhibitors. The cathodic curves indicate that the reduction of proton at the steel surface happens with an activating mechanism. Adsorption of T3 on the steel surface obeys to the Langmuir adsorption model. Effect of temperature studied between 308 and 353K shows that efficiency remains almost constant.
Keywords: Telechelic; Inhibition; Corrosion; Steel; Acid
A study on low cost-high conducting fluorine and antimony-doped tin oxide thin films by E. Elangovan; K. Ramamurthi (pp. 183-196).
Thin films of undoped, fluorine- and antimony-doped tin oxide on glass at 400°C was prepared by spray pyrolysis technique. Tin chloride (SnCl2), ammonium fluoride (NH4F), and antimony trichloride (SbCl3) were used as source for tin (Sn), fluorine (F), and antimony (Sb), respectively. To ensure the control of solution concentration on growth rate, fluorine-doped tin oxide (SnO2:F) thin films were first prepared with different amount of tin precursor, in the range of 5–12g, which has resulted in deposition of films with different thickness values. The optimum amount of tin precursor found from this study (11g) was fixed constant for preparing SnO2 films with different doping levels of F and Sb. From the X-ray diffraction analyses, it is understood that the preferred orientation of SnO2:F films is dependent on their thickness and the solution concentration. The variation in the solution concentration and orientation of the films was reflected in their morphology as examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM studies showed that the variation in the solution concentration lead to different grain shapes for different orientations. The AFM study showed that the RMS roughness of undoped films reduced considerably from 86 to 24nm due to fluorine doping (15wt.%), whereas the antimony doping (2wt.%) has no significance effect on RMS roughness (93nm). The electrical properties of the films were examined by a Hall measurements setup in van der Pauw configuration. A minimum sheet resistance of 1.75 and 2.17Ω/ were obtained for F and Sb doped films, respectively. From the optical studies, it is found that the transmittance of undoped films increased from 42% to a maximum 85% on 30wt.% fluorine doping, whereas that has been decreased to a minimum of 12% on 4wt.% antimony doping (800nm). A discussion on the effect of type of dopants and their concentration on the structural, electrical and optical properties of the SnO2 film have been presented.
Keywords: PACS; 68.37.Hk (scanning electron microscopy (SEM)); 68.37.Ps (atomic force microscopy (AFM)); 68.55.Jk (structure and morphology, thickness, crystalline orientation and texture)Semiconductors; Tin oxide thin films; Spray pyrolysis; SnCl; 2; precursor and electrical properties
The origin of faceting of ultraflat gold films epitaxially grown on mica by Björn Lüssem; Silvia Karthäuser; Hans Haselier; Rainer Waser (pp. 197-202).
A two-step deposition process for the formation of atomically flat gold films on mica is developed. The process starts with a high deposition rate followed by a 1:100 reduced rate. Using this combination a completely wetting of mica by gold resulting in a two-dimensional growth mode and finally extremely flat gold films with large terraces are achieved. Additionally hexagonal faceting of the gold films on mica is observed at moderate temperatures which can be related to the relaxation of stress caused by different thermal coefficients of expansion of mica and gold. The stress release leads to the generation of misfit dislocations that glide along the (100) planes producing facets on the surface. Annealing experiments in a UHV-STM and thermogravimetry point to the inset of intensified hexagonal faceting due to the starting decomposition of mica at elevated temperatures.
Keywords: PACS; 68.37.Ef; 68.37.PsGold on mica; Faceting; 2D growth; Thermogravimetry; Dislocation glide
Effects of Al content on properties of Al–N codoped ZnO films by Yu-Jia Zeng; Zhi-Zhen Ye; Jian-Guo Lu; Li-Ping Zhu; Dan-Ying Li; Bing-Hui Zhao; Jing-Yun Huang (pp. 203-207).
N doped and Al–N codoped ZnO films were prepared by dc reactive magnetron sputtering with a series of metal–Zn targets having different Al contents. The best p-type electrical properties of codoped ZnO, such as carrier concentration of 2.52×1017cm−3, resistivity of 28.3Ωcm can be realized by using 0.4at.% Al target. Results of Hall effect and X-ray photoelectron spectroscopy (XPS) measurements confirm that the presence of Al indeed facilitates the incorporation of N through formation AlN bonds in codoped ZnO. Finally, a new judgement for codoping effect in ZnO is proposed tentatively: the best codoping effect can be realized when the codoped ZnO films possess a closest (002) d-spacing value to the nominally undoped ZnO.
Keywords: PACS; 71.55.Gs; 61.72.Vv; 73.40.Lq; 81.15.CdZnO; Al–N codoping; Reactive magnetron sputtering; X-ray photoelectron spectroscopy (XPS)
Study on cord/rubber interface at elevated temperatures by H-pull test method by M. Jamshidi; F. Afshar; N. Mohammadi; S. Pourmahdian (pp. 208-215).
Cords are used as reinforcing materials in rubber compounds. To increase cord/rubber interfacial adhesion, they are coated by an adhesive (usually based on resorcinol–formaldehyde–latex). These composites are used in many sectors such as tire and belt industries. Cord/rubber adhesion strength is an important aspect to determine the durability of system.Due to temperature increase during running tires, the adhesion energy becomes different from initial one. To study cord/rubber interface at elevated temperatures, H-adhesion test method was used. H-pull test is a simple method for adhesion evaluation at ambient temperature, so it is usually used for material quality control.In this research, cord/rubber systems were vulcanized at different temperatures and H-adhesion of samples were evaluated at elevated temperatures. Also cord/rubber interface was studied by ATR analyze to determine interfacial interactions kind.
Keywords: H-adhesion; RFL; Cord to rubber adhesion; Interfacial interactions
Effects of dry etching processes on optical properties of ZnTe surface layers in ultraviolet region by S. Wu; Z.Q. Ren; W.Z. Shen; H. Ogawa; Q.X. Guo (pp. 216-221).
We report on the ultraviolet reflection measurements of zinc telluride (ZnTe) crystals exposed to CH4/H2 gases under different rf plasma powers in combination with the critical points model. The effects of dry etching on optical properties such as dielectric function, refractive index and distinction coefficient in perturbed ZnTe surface layers have been investigated in the photon energy range of 3–6eV. All of the optical coefficients decrease with the increase of plasma power, which has been explained as the effects of the etch-induced defects. The temperature-dependent ultraviolet reflection measurements on the reactive ion etching (RIE) ZnTe crystals reveal resembled effects while either increasing the rf power or increasing the experimental temperature due to the similar role of the electron–phonon and electron-defect scattering.
Keywords: PACS; 78.68.+m; 81.65.Cf; 78.66.Hf; 78.20.CiDry etching processes; Optical properties; Ultraviolet; Zinc telluride (ZnTe)
Sputter cleaning and annealing of zinc-blende MnTe surface—XPS study by R.J. Iwanowski; M.H. Heinonen; E. Janik (pp. 222-230).
This paper, being a complementary one to our earlier report (Chem. Phys. Lett. 387 (2004) 110), presents a detailed description of the surface cleaning method applied for molecular beam epitaxy (MBE)-grown zinc-blende (zb)-MnTe epilayers. In particular, surface compositional changes induced by multistep Ar+ ion sputtering (with beam energy, Ei, fixed between 0.5 and 2.0keV) and subsequent annealing of zb-MnTe crystal have been studied by using X-ray photoelectron spectroscopy (XPS). It was found that Ar+ ion bombardment with Ei=1.5keV appeared as the crucial preparation step (either in multistep- or in post-anneal sputtering), which provided an efficient removal of the surface oxides and contaminants and led to nearly stoichiometric surface composition, namely [Te]/[Mn]=0.97. Detailed analysis of the Mn 2p core-level spectrum (acquired in Mg Kα mode) for clean zb-MnTe surface exhibited good consistency with the results of the relevant analysis reported earlier (see the reference above).
Keywords: PACS; 79.60; 68.35; 71.20X-ray photoelectron spectroscopy; Single crystal surface; Manganese telluride; Ion bombardment; Univalent manganese
Evolution of oxidation states in vanadium-based catalysts under conventional XPS conditions by Y. Suchorski; L. Rihko-Struckmann; F. Klose; Y. Ye; M. Alandjiyska; K. Sundmacher; H. Weiss (pp. 231-237).
The stability of different vanadium-based catalysts for the selective oxidation of small hydrocarbons under the ultra-high vacuum (UHV) conditions of standard X-ray photoelectron spectroscopy (XPS) was studied by using a multi-purpose surface analysis apparatus which allows time spans of only a few minutes between the sample transfer into vacuum and the first photoelectron spectrum. For vanadium phosphorus oxide catalysts a significant dependence of the average vanadium oxidation state on the time of exposure to the UHV was observed, with a substantial decrease of the V+5/V+4 ratio within only a few minutes. A much less pronounced reduction was found for alumina-supported VO x catalysts. The observed changes are predominantly due to the vacuum environment with a rather minor (if at all) contribution of the X-ray excitation.
Keywords: PACS; 82.65.+r; 82.80.PvVPO catalysts; VO; x; catalysts; Supported catalysts; XPS
Thermionic contrast between the mean work functions effective for thermal positive-ionic and electronic emissions from polycrystalline tungsten surfaces heated in vacuum: comparison between theory and experiment by Hiroyuki Kawano (pp. 238-245).
To study the thermionic contrast of polycrystalline surfaces consisting of many patchy faces with different local work functions, those mean work functions ( ϕ+ and ϕe) effective for thermal positive-ionic and electronic emissions from a polycrystalline tungsten surface heated in a high vacuum were measured as a function of surface temperature and found to be 5.18±0.02 and 4.60±0.02eV, respectively, in a temperature range (≳2000K) high enough to keep the surface virtually clean. Consequently, the thermionic contrast (Δ ϕ* ϕ+− ϕe) was determined experimentally to be 0.58±0.03eV. They are in good agreement with literature values ( ϕ +=5.11±0.04eV, ϕe=4.59±0.01eV and Δ ϕ *=0.52±0.04eV) reported with essentially clean surfaces of polycrystalline tungsten. By using those data on both local work function and fractional area reported with patchy faces of polycrystalline tungsten, ϕ+ and ϕe at 2000−2300K are theoretically evaluated to be 5.15±0.03 and 4.63±0.01eV, respectively, thereby yielding Δ ϕ*=0.52±0.03eV. Each of these theoretical values agrees well with each of the experimental ones within the errors of ±0.04eV. In addition, Δ ϕ *=0 deduced theoretically with monocrystalline tungsten consists with literature values (from −0.05 to 0.06eV, affording 0.01±0.04eV as average) determined experimentally by several groups of workers. These results lead to the conclusion that the thermionic contrast for polycrystalline tungsten is 0.54±0.04eV in contrast to Δ ϕ*=0 for monocrystalline tungsten.
Keywords: PACS; 73.20.−rThermionic contrast; Work function; Thermal positive ion emission; Monocrystalline metal surfaces; Tungsten
Diamond-like carbon coatings on microdrill using an ECR-CVD system by H.Y. Ueng; C.T. Guo (pp. 246-256).
The Ti/TiN/TiCN/DLC multilayer coating on the microdrill was processed in a hybrid PVD-ECRCVD coating system (HBS900). Functionally gradient Ti/TiN/TiCN supporting multilayer was pre-deposited initially on the microdrill in order to improve the adhesion strength of the DLC films. The following dry lubricant coating on it is composed of amorphous, diamond-like carbon (DLC) deposited by ECRCVD plasma in the same recipient. For drilling applications, the combination of hard/soft coating layers, TiN/TiCN/DLC, allows it to improve chip flow with a lowered coefficient of friction and reduced cutting force. In view of further cost reduction, technically the Ti/TiN/TiCN/DLC multilayer coating on microdrill could serve this purpose best. Functionally, in adapting a microdrill coated with DLC film, the quality of hole after inspection was found sufficiently superior than that of uncoated ones, and the drilling lifetime obtained a significant improvement reaching about 2.5 times.
Keywords: DLC; ECR; Raman; Microdrill
Friction behaviors of hydrogenated diamond-like carbon film in different environment sliding against steel ball by Hongxuan Li; Tao Xu; Chengbing Wang; Jianmin Chen; Huidi Zhou; Huiwen Liu (pp. 257-265).
Friction behaviors of hydrogenated diamond-like carbon (DLC) film sliding against steel ball were investigated on a ball-on-disk test rig in different environment. The worn surface morphology of the steel ball was observed on a scanning electron microscope (SEM), and the chemical states of some typical elements on the worn surface of DLC film were investigated by means of X-ray photoelectron spectroscopy (XPS). The result showed that the friction behaviors of hydrogenated DLC film were very sensitive to the testing environment. In dry N2, the film provided a much low and stable friction coefficient of about 0.035. When the friction tests were performed in higher relative humidity and in dry O2, higher and unstable friction coefficient of more than 0.2 was obtained. It was found that in oxygen and/or water containing environments, the transferred carbon-rich layer on the counterpart steel ball was inhibited, and the friction-induced oxidation of the DLC film surface and the chemical reactions between the DLC film and steel ball were involved in the friction processes, which accounted for the higher friction coefficient of the DLC film. The roles of environment in the friction behaviors of DLC film were discussed in terms of the friction-induced physical and chemical interactions among the DLC film, steel ball and water and/or oxygen molecules.
Keywords: Hydrogenated DLC film; Friction behaviors; Environment; Interaction
Fibrillar polyaniline/diatomite composite synthesized by one-step in situ polymerization method by Xingwei Li; Xiaoxuan Li; Gengchao Wang (pp. 266-270).
A fibrillar polyaniline/diatomite composite was prepared by one-step in situ polymerization of aniline in the dispersed system of diatomite, and was characterized via Fourier-transform infrared spectra (FT-IR), UV–vis–NIR spectra, wide-angle X-ray diffraction (WXRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM), as well as conductivity. Morphology of the composite is uniform nanofibers, which the diameters of nanofibers are about 50–80nm. The conductivity of polyaniline/diatomite composite contained 28% polyaniline is 0.29Scm−1 at 25°C, and temperature of thermal degradation has reached 493°C in air. The composite has potential commercial applications as fillers for electromagnetic shielding materials and conductive coatings.
Keywords: Polyaniline; Diatomite; Nanofibers
Surface properties of treated ITO anodes for organic light-emitting devices by Zhong Zhi You; Jiang Ya Dong (pp. 271-276).
The effect of oxygen plasma treatment on the surface properties of indium-tin oxide (ITO) anodes and the changes in surface properties of treated ITO anodes with aging time were investigated by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) measurements. It was observed that oxygen plasma treatment increased the oxygen concentration, decreased the carbon concentration and raised the ITO work function, and thereby improved the surface properties of ITO. With the increase of aging time, however, the improved ITO surface properties tended to decay and the ITO work function decreased. In addition, the aging effect of treated ITO anodes on the performance of organic light-emitting devices (OLEDs) was studied with respect to the driving voltage, electroluminescent luminance and efficiency. Experimental results reveal that the ITO anodes aged for various times result in significant differences in electrical and optical characteristics, which become worse as the aging time increases.
Keywords: PACS; 81.40.−z; 42.70.Nq; 85.60.JbSurface properties; Indium-tin oxide (ITO); Organic light-emitting device (OLED)
Ion-, photoelectron- and laser-assisted analytical investigation of nano-structured mixed HfO2–SiO2 and ZrO2–SiO2 thin films by L. Armelao; D. Bleiner; V. Di Noto; S. Gross; C. Sada; U. Schubert; E. Tondello; H. Vonmont; A. Zattin (pp. 277-294).
In this study, the surface and depthwise composition of hafnium- and zirconium-based inorganic–organic hybrid layers, as well as of binary HfO2–SiO2 and ZrO2–SiO2 thin films, obtained by calcination at high temperature ( T=800°C) of the hybrid films, were analysed by using different analytical methods which can deliver complementary information on chemical composition and both in-depth and lateral distribution of the species. In particular, X-ray photoelectron spectroscopy (XPS) was used to investigate the chemical composition of the thin films (quantitative analysis, oxidation states, nature of the interaction between host matrix and guest species) on the surface as well along the film thickness. The depthwise distribution of the involved species was thoroughly investigated by means of secondary ion mass spectrometry (SIMS). Information concerning the lateral distribution of the species was gained also by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).Finally, the dielectric response of two samples was characterized through broadband dielectric spectroscopy, which provided a value of ɛ′( ω) ranging from 7.5 to 9.5 for a film without the cluster, while in a sample embedding the hafnium cluster these values range in the interval 7.2–7.4.The information obtained by the different analytical methods demonstrated the formation of a homogeneous in-depth nanocomposition of the thin films, which would be suitable for frontier applications.
Keywords: Multicomponent oxides; Sol–gel; ZrO; 2; HfO; 2; Thin films; LA-ICP-MS; XPS; SIMS
XPS study of the ultrathin a-C:H films deposited onto ion beam nitrided AISI 316 steel by S. Meskinis; M. Andrulevicius; V. Kopustinskas; S. Tamulevicius (pp. 295-302).
Effects of the steel surface treatment by nitrogen ion beam and subsequent deposition of the diamond-like carbon (hydrogenated amorphous carbon (a-C:H) and nitrogen doped hydrogenated amorphous carbon (a-CN x:H)) films were investigated by means of the X-ray photoelectron spectroscopy (XPS). Experimental results show that nitrogen ion beam treatment of the AISI 316 steel surface even at room temperature results in the formation of the Cr and Fe nitrides. Replacement of the respective metal oxides by the nitrides takes place. Formation of the CN bonds was observed for both ultrathin a-C:H and ultrathin a-CN x:H layers deposited onto the nitrided steel. Some Fe and/or Cr nitrides still were presented at the interface after the film deposition, too. Increased adhesion between the steel substrate and hydrogenated amorphous carbon layer after the ion beam nitridation was explained by three main factors. The first two is steel surface deoxidisation/passivation by nitrogen as a result of the ion beam treatment. The third one is carbon nitride formation at the nitrided steel–hydrogenated amorphous carbon (or a-CN x:H) film interface.
Keywords: PACS; 81.15.Jj; 81.65.−b; 81.05.Uw; 68.55; 82.80.PvHydrogenated amorphous carbon films; Diamond-like carbon; Steel; Ion beam treatment and deposition; X-ray photoelectron spectroscopy
Surface properties and conductivity of bis(2-ethylhexyl) sulfosuccinate-containing polypyrrole by Kada Boukerma; Mária Omastová; Pavol Fedorko; Mohamed M. Chehimi (pp. 303-314).
Polypyrrole (PPy) was chemically synthesized by oxidative polymerization of pyrrole in aqueous solution containing an oxidant, ferric chloride, and an anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT). The results of elemental analysis confirmed that the surfactant is incorporated into the PPy structure. The presence of the anionic surfactant AOT in polymerization mixture influences the properties of chemically prepared polypyrrole due to bonding the anionic part of the surfactant molecule to the PPy chains as proved by X-ray photoelectron spectroscopy (XPS) analysis. Scanning electron microscopy study showed that the presence of the AOT affects the morphology of the product. A more compact powder morphology and reduced size of the PPy globules were revealed. The addition of AOT to the reaction mixture results in a significantly increased conductivity: PPy synthesized in polymerization solution containing molar ratio [pyrrole]/[AOT]=7 reached conductivity as high as 27Scm−1, while the same experiment performed in the absence of AOT yielded a polymer with conductivity of 3.9Scm−1 only.
Keywords: PACS; 61.10.Yh (other X-ray techniques for structure analysis); 72.80.−r (conductivity of specific materials); 73.61.Ph (Polymers; organic compounds)Polypyrrole; AOT; XPS; Conductivity; SEM
Conducting atomic force microscopy for nanoscale electron emissions from various diamond-like carbon films by Dongping Liu; Günther Benstetter (pp. 315-321).
Conducting atomic force microscopy (C-AFM) has been used to compare the nanoscale electron emissions from hydrogen-free (a-C), hydrogenated (a-C:H), and tetrahedral (ta-C) diamond-like carbon films. The current measurements are performed on the locations where the low-resistant surface layers are removed. The measurements show the uniform electron emissions from a-C:H and ta-C films. The inhomogeneous electron emission from the a-C film is primarily due to the conducting graphite clusters inside the film. The analysis of Fowler–Nordheim tunnelling currents indicates the formation of filament-like emission channels inside these films. The implications of film structures for electron field emissions are discussed.
Keywords: Conducting atomic force microscopy; Diamond-like carbon; Electron emission
Pulse width and energy influence on laser micromachining of metals in a range of 100fs to 5ps by R. Le Harzic www.jenlab.de; D. Breitling; M. Weikert; S. Sommer; C. Föhl; S. Valette; C. Donnet; E. Audouard; F. Dausinger (pp. 322-331).
Micromachining of steel, Cu and Al is studied. Ablation depths per pulse are deduced for laser pulse durations between 100fs and 5ps for fluences in the range of 150mJcm−2 to 20Jcm−2. The evolution of ablation rates allows to evidence a low and a high fluence regime. Ablation thresholds and penetration depths are deduced as functions of pulse duration. While in the low fluence regime the penetration depth is close to the theoretical optical penetration depth, at higher fluences the effective heat penetration depth is 10–20 times bigger with also higher ablation thresholds. Even in the femtosecond range thermal ablation processes occur and reduce quality, accuracy and efficiency of micromachining. Additionally, the latter are influenced by strong beam distortions due to nonlinear interaction between the radiation and the atmospheric gas. In the case of steel and Cu, the pulse duration seems not to affect microprocessing, but it is demonstrated to play a role for Al for pulses between 1 and 5ps.
Keywords: PACS; 79.20.Ds; 42.62.Cf; 81.65.CfLaser; Femtosecond; Picosecond; Ablation; Pulse duration; Energy; Heat penetration; Thermal effects
Interaction of anti-adhesive silicone films with UV embossing resin by Y.H. Yan; M.B. Chan-Park; W.C. Ching; C.Y. Yue (pp. 332-339).
The durability of two silicone films, which were formed from silicone-based release agents with different molecular weights (MW), as anti-adhesive coatings for molds used for UV embossing was investigated. Flat electroless nickel-plated polyester stamp and UV-curable polyethylene glycol diacrylate (PEGDA) were the mold and molding material, respectively. The surface chemical composition of the silicone films and the PEGDA moldings was analyzed by X-ray photoelectron spectroscopy (XPS) as a function of molding times using the same nickelized polyester stamp. Silicone transfer was found to occur from the silicone films to the moldings with increased number of moldings. The silicone film formed from the release agent with the higher MW had the poorer durability. Two mechanisms are proposed for the material transfer.
Keywords: Anti-adhesion; Silicone-based release agent; Thin film; UV molding; XPS
Photoemission study of chemisorption and Fermi-level pinning at K/GaAs(100) interface with synchrotron radiation by M.H. Sun; T.X. Zhao; C.Y. Jia; P.S. Xu; E.D. Lu; C.C. Hsu; Hang Ji (pp. 340-345).
The adsorption of K on the n-GaAs(100) surface was investigated by X-ray photoelectron spectroscopy (XPS) and synchrotron radiation photoemission spectroscopy (SR–PES). The Ga3d and As3d core level was measured for clean and K adsorbed GaAs(100) surface. The adsorption of K induced chemical reaction between K and As, and the K–As reactant formed when the K coverage θ>1ML. The chemical reaction between K and Ga did not occur, but Ga atoms were exchanged by K atoms. From the data of band bending, the Schottky barrier is 0.70eV. The Fermi-level pinning was not caused by defect levels. The probable reason is that the dangling bonds of surface Ga atoms were filled by the outer-shell electrons of K atoms, forming a half-filled surface state. The Fermi-level pinning was caused by this half-filled surface state.
Keywords: X-ray photoelectron spectroscopy; Fermi-level pinning; Schottky barrier
Preparation of silver nanopatterns on DNA templates by Shuxi Dai; Xingtang Zhang; Tianfeng Li; Zuliang Du; Hongxin Dang (pp. 346-353).
Patterns of silver metal were prepared on DNA networks by a template-directed selective deposition and subsequent metallization process. Scanning force microscopic observations and XPS investigations demonstrated that uniform networks of nanosized silver metal clusters formed after incubation of DNA LB films with silver ions and subsequent chemical reduction of silver ions/DNA films samples. The results showed that this template-directed metallization on DNA LB films provided a simple and effective method for the construction of functional nanocomposite films.
Keywords: Langmuir–Blodgett films (LB films); DNA; Metallization; Atomic force microscopy (AFM); X-ray photoelectronspectroscopy (XPS)
Impact of laser scribing for efficient device separation of LED components by E.K. Illy; M. Knowles; E. Gu; M.D. Dawson (pp. 354-361).
Laser scribing of light emitting diode (LED) components on sapphire substrates is shown in this paper to be a viable method of device separation. Three key measurements revealing the effects of UV laser scribing on the LED component performance are discussed and compared for laser scribing at 255 and 355nm. The differences in these two UV wavelengths are further discussed in terms of quality; comparing pulse energies and pulse repetition frequencies for UV ablation of sapphire. In general, these results prove laser processing can be used as an effective high volume manufacturing procedure for substrate separation.
Keywords: PACS; 85.60.Jb; 87.80.MjLaser scribing; Sapphire scribing; Laser dicing; UV wavelengths; LEDs
Interface study of transition metal (Fe, Zr) on 4H–SiC(0001)Si face: photoemission electron microscopy and soft X-ray fluorescence spectroscopy by M. Hirai; C. Kamezawa; S. Azatyan; Z. An; T. Shinagawa; T. Fujisawa; M. Kusaka; M. Iwami (pp. 362-366).
We have studied interface electronic structure of transition metal film (Fe, Zr)/4H–SiC (substrate) contact systems by using a photoemission electron microscopy (PEEM) and a soft X-ray fluorescence spectroscopy (SXFS). PEEM can show surface micro- and/or nano-structures, whereas SXFS can tell details of chemical bonding states.For specimens of Fe(10nm)/4H–SiC(0001)Si face contact system annealed at 300–900°C, PEEM images have shown dramatic change in surface morphology above 550°C, where the Si L2,3 fluorescence spectra can be explained by considering formation of iron silicides.On the other hand, PEEM images and the Si L2,3 fluorescence spectra for specimens of Zr(film)/4H–SiC(0001)Si face contact system annealed at 650–1100°C have indicated that interfaces of specimens are stable up to 1100°C without any reaction.
Keywords: PACS; 68.35.−p; 73.20.−rPEEM; SXFS; 4H–SiC; Silicide; Fe; Zr
Effect of substrate temperature on electrochromic properties of spray-deposited Ir-oxide thin films by P.S. Patil; R.K. Kawar; S.B. Sadale (pp. 367-374).
Electrochromic iridium oxide thin films were prepared by using a simple and inexpensive spray pyrolysis technique onto fluorine doped tin oxide (FTO)-coated glass substrates, from iridium chloride solution. The substrate temperature was varied between 250 and 400°C. The as-deposited samples were amorphous. The electrochromic properties of thin films were studied in aqueous electrolyte (0.5N H2SO4) using cyclic voltammetry (CV), chronoamperometry (CA) and spectroelectrochemical techniques. The films exhibit anodic electrochromism upon intercalation and deintercalation of H+ ions. The colouration efficiency at 630nm was calculated and found maximum for I250 sample, owing its hydration.
Keywords: Spray pyrolysis; Thin films; Electrochromism; Iridium oxide
Inhibitive action of bipyrazolic type organic compounds towards corrosion of pure iron in acidic media by A. Chetouani; B. Hammouti; T. Benhadda; M. Daoudi (pp. 375-385).
Inhibitory effect of some new synthesized bipyrazole compounds, namely, N, N-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]- N-(4-methylphenyl)amine (P1) and methyl-1-[((methylphenyl){[3-(methoxycarbonyl)-5-methyl-1H-pyrazol-1-yl]methyl}amino)methyl]-5-methyl-1H-pyrazole-3-carboxylate (P2) on corrosion of pure iron in 1M HCl solution has been studied using chemical technique as weight loss and electrochemical techniques as potentiodynamic polarization, linear polarization and impedance. The inhibition efficiencies obtained from gravimetric, cathodic Tafel plots, linear polarization resistance and EIS methods are in good agreement. The results obtained reveal that these compounds are efficient inhibitors. The inhibition efficiency increases with the increase of inhibitor concentration to reach 93% for P1 at 2.5×10−4M. Potentiodynamic polarisation studies clearly reveal that P1 and P2 act as mixed-type inhibitors without change of the mechanism of hydrogen evolution. The temperature effect on the corrosion behaviour of iron in 1M HCl without and with the inhibitors at 2.5×10−4M has been studied in the temperature range from 298 to 353K. EIS measurements show that the increase of the transfer resistance with the inhibitor concentration. The inhibitors are adsorbed on the iron surface according to the Langmuir adsorption isotherm model. From the adsorption isotherm some thermodynamic data for the adsorption process (K andΔGads°) are calculated and discussed.
Keywords: Bipyrazole; Inhibition; Corrosion; Iron; Acid; Langmuir
Effect of Ar+ ion implantation on the nano-mechanical properties and microstructure of single crystal silicon by Rong Sun; Tao Xu; Qun-ji Xue (pp. 386-392).
The effect of argon ion implantation on the nano-machanical properties of single crystal Si was examined making use of nano-indentation and nano-scratch tests. The morphologies of the scratched tracks of the unimplanted Si and that implanted at a moderate Ar+ fluence were observed on a scanning electron microscope, while the changes in the microstructure of the single crystal Si by Ar+ implantation were investigated on a transmittance electron microscope. It was found that the implantation of Si at a small or moderate fluence of Ar+ below 1×1015ions/cm2 had little effect on the surface roughness and a minor effect on the surface nano-hardness. At the same time, the implantation of Si with Ar+ at a moderate fluence up to 1×1016ions/cm2 led to a significant increase in the critical load. This was attributed to the desired changes in the microstructures of the single crystal Si by Ar+ implantation at a proper fluence. Namely, the Si surface implanted with Ar+ at a moderate fluence was composed of nano-sized polycrystalline Si uniformly distributed in amorphous Si matrix, which contributed to significantly increase the nano-scratch resistance and surface toughness of the single crystal silicon. It was suggested to implant the single crystal Si at an Ar+ fluence of 1×1016ions/cm2 so as to acquire the optimized modification effect.
Keywords: Single crystal silicon; Ion implantation; Nano-scratch; Nano-indentation; Microstructure
ToF-SIMS imaging: a valuable chemical microscopy technique for paper and paper coatings by Pedro Fardim; Bjarne Holmbom (pp. 393-407).
The distribution of papermaking chemicals on the surface of various uncoated and coated papers was investigated by ToF-SIMS, FE-SEM, EDS, and XPS. Four paper samples, two office papers, one matte-coated and one traditionally coated paperboard were investigated with the aim of evaluation of chemical microscopy methods for examination of morphological and chemical heterogeneities on paper surfaces. Distribution of fillers, pigment particles, size, optical brightener, latex and other paper and coating components was assessed. Application of Au–Pd treatment on paper and coating surfaces prior to ToF-SIMS imaging increased the secondary ion counts for the region of low intensity peaks and improved the chemical mapping of papermaking and coating chemicals. ToF-SIMS imaging is shown to be a valuable and promising technique for chemical microscopy of paper surfaces.
Keywords: Pulp fibres; Coating; Latex; Sizing; FE-SEM; XPS; EDS; ToF-SIMS
The inhibition effect of some amino acids towards the corrosion of aluminum in 1M HCl+1M H2SO4 solution by H. Ashassi-Sorkhabi; Z. Ghasemi; D. Seifzadeh (pp. 408-418).
The inhibition effect of some amino acids towards the corrosion of aluminum in 1M HCl+1M H2SO4 solution was investigated using weight loss measurement, linear polarization and SEM techniques. The results drawn from the different techniques are comparable. The used amino acids were alanine, leucine, valine, proline, methionine, and tryptophan. The effect of inhibitor concentration and temperature against inhibitor action was investigated. It was found that these amino acids act as good inhibitors for the corrosion of aluminum in 1M HCl+1M H2SO4 solution. Increasing inhibitor concentration increases the inhibition efficiency and with increasing temperature the inhibition efficiency decreases. It was found that adsorption of used amino acids on aluminum surface follows Langmuir and Frumkin isotherms.
Keywords: Corrosion; Inhibitor; Amino acid; Mixed acidic media; Aluminum
Growth of SrTiO3 films on Si(001)–Sr(2×1) surfaces by Md. Nurul Kabir Bhuiyan; Hiroaki Kimura; Toyokazu Tambo; Chiei Tatsuyama (pp. 419-424).
The growth and characterization of a SrTiO3 film by molecular beam deposition process have been studied. After Sr deposition on the chemically formed SiO2/Si surface, a stable and well-ordered Si(001)–Sr(2×1) surface was formed. The SrTiO3 films were grown on the Si(001)–Sr(2×1) surface at 80°C in a molecular oxygen partial pressure of approximately 3×10−7Torr and subsequently in situ post-annealed at various high temperatures without oxygen supply in ultra-high vacuum (<2.5×10−9Torr). The combined reflection high-energy electron diffraction, X-ray diffraction and atomic force microscopy analyses suggest that the SrTiO3 film grown at 80°C is amorphous nature. The lowest post-annealing temperature from amorphous-to-crystal transformation of the SrTiO3 film is approximately 485°C. The quality of the crystalline SrTiO3 films is further improved by post-annealing at temperatures between 600 and 700°C.
Keywords: PACS; 68.55.a; 61.14.HgSrTiO; 3; films; Si(0; 0; 1) substrates; MBD; RHEED; XRD; AFM
Modification of PS films by combined treatment of ozone aeration and UV irradiation in aqueous ammonia solution for the introduction of amine and amide groups on their surface by Takurou N. Murakami; Yoshinori Fukushima; Yoshiaki Hirano; Yoshikazu Tokuoka; Mitsuo Takahashi; Norimichi Kawashima (pp. 425-432).
We report the surface modification of PS films treated in aqueous ammonia solution and distilled water by a combination of ozone aeration and UV irradiation. The surface properties of the treated film were investigated by contact angle measurements, X-ray photoelectron spectroscopy (XPS), and attenuated total-reflection FT-IR (ATR/IR) measurements. The water contact angle of the treated films decreased with increasing treatment time and the film surface became hydrophilic. Treatment in aqueous ammonia solution introduced amide or amino-groups onto the PS surface. Hydroxyl groups and carbonic acid were also produced on the surface by treatment in aqueous ammonia solution. However, the treatment in water introduced only hydroxyl and carbonyl groups onto the surface. The introduction of amine and amide onto the PS film surface is due to the reaction of the PS film with amino radicals, the reaction of ammonia with reactive species on the PS film, and the ammonolysis of esters formed on the PS surface.
Keywords: Surface modification; Polymer; Ozone; UV; Amide; Amine
Erratum to “Time resolved schlieren study of sub-picosecond and nanosecond laser transfer of biomaterials� [Applied Surface Science 247 (2005) 584–589]
by I. Zergioti; A. Karaiskou; D.G. Papazoglou; C. Fotakis; M. Kapsetaki; D. Kafetzopoulos (pp. 433-433).