Applied Surface Science (v.252, #10)
Study on hydrophilicity of polymer surfaces improved by plasma treatment by Jiangnan Lai; Bob Sunderland; Jianming Xue; Sha Yan; Weijiang Zhao; Melvyn Folkard; Barry D. Michael; Yugang Wang (3375-3379).
Surface properties of polycarbonate (PC), polypropylene (PP), polyethylene terephthalate (PET) samples treated by microwave-induced argon plasma have been studied with contact angle measurement, X-ray photoelectron spectroscopy (XPS) and scanned electron microscopy (SEM). It is found that plasma treatment modified the surfaces both in composition and roughness. Modification of composition makes polymer surfaces tend to be highly hydrophilic, which mainly depended on the increase of ratio of oxygen-containing group as same as other papers reported. And this experiment further revealed that C＝O bond is the key factor to the improvement of the hydrophilicity of polymer surfaces. Our SEM observation on PET shown that the roughness of the surface has also been improved in micron scale and it has influence on the surface hydrophilicity.
Keywords: Plasma; Polymer; SEM; XPS; Contact angle;
X-ray photoelectron spectroscopy study of sputter-annealed Ni2.1Mn0.9Ga surface by C. Biswas; S.R. Barman (3380-3385).
The modifications in surface composition of Ni2.1Mn0.9Ga ferromagnetic shape memory alloy have been investigated using X-ray photoelectron spectroscopy (XPS) under various sputtering and annealing conditions. XPS core-level spectra show that sputtering makes the surface Ni rich. However, by annealing, the Mn content at the surface increases and at about 390 ° C the bulk composition is restored. The valence band spectra show evidence of Ni related extra states for the sputtered surface, which decrease with annealing. This behavior is in agreement with the change in surface composition derived from the core-level spectra.
Keywords: Surface composition; X-ray photoelectron spectroscopy; Ni–Mn–Ga alloy; Sputter; Anneal;
Preparation and characterization of pulsed laser deposition (PLD) SiC films by Y.H. Tang; T.-K. Sham; D. Yang; L. Xue (3386-3389).
Si K-edge XAFS was used to characterize a stoichiometric SiC film prepared by pulsed KrF laser deposition. The film was deposited on a p-type Si(1 0 0) wafer at a substrate temperature of 250 °C in high vacuum with a laser fluence of ∼5 J/cm2. The results reveal that the film contains mainly a SiC phase with an amorphous structure in which the Si atoms are bonded to C atoms in its first shell similar to that of crystalline SiC powder but with significant disorder.
Keywords: Pulsed laser deposition; SiC film; Si K-edge;
The effect of nonmagnetic defects on magnetic behavior for multilayers Ta/Co/Co3O4/Ta by Yaxin Wang; Wei Tian; Jie Xiong; Yixing Wang; Liang Sun; Qi Li; Biao You; An Hu; Hongru Zhai; Mu Lu (3390-3393).
The exchange bias field H E was much higher for Ta/Co/Co3O4/Ta than Ta/Co/Co3O4, fabricated in a magnetron sputtering system under the same experimental conditions. The XPS analysis showed that Ta atoms of cap layer for Ta/Co/Co3O4/Ta diffused into Co3O4 layer and reduced Co3O4, and introduced some nonmagnetic defects into the AFM layer. The dilution of the AFM layer led to the formation of volume domains. We believed that the higher H E for the multilayers Ta/Co/Co3O4/Ta was primarily attributed to the formation of volume domain due to some nonmagnetic defects in AFM layer.
Keywords: Multilayers; Exchange bias; XPS; Nonmagnetic defects;
Theoretical investigation of the intrinsic piezoelectric properties for tetragonal BaTiO3 epitaxial films by Jun Ouyang; R. Ramesh; A.L. Roytburd (3394-3400).
The orientation dependences of the converse longitudinal piezoelectric constant d 33,f, and the in-plane converse piezoelectric constant e 31,f, are calculated for tetragonal barium titanate epitaxial films. The calculations demonstrate that both e 31,f and d 33,f have their maximum values along an axis close to the (1 1 1) direction of the pseudo-cubic system, which are similar to the orientation dependence results for a tetragonal BaTiO3 single crystal. The calculated piezoelectric constants for a (1 1 1) oriented BaTiO3 epitaxial film (e 31,f = −23 C/m2, d 33,f = 124 pm/V) suggest that it is a good candidate material for lead-free MEMS applications.
Keywords: Barium titanate; Ferroelectric films; Piezoelectric effect; Lead-free; MEMS;
Study by AES of the titanium nitruration in the growing of TiN thin films by PLD technique by C. Gonzalez-Valenzuela; L. Cota; R. Gonzalez-Valenzuela; W. de la Cruz; A. Duarte-Möller (3401-3405).
A series of different TiN x thin films were grown by PLD. The purpose for this work was to study through the AES interpretation, how the different conditions of the partial pressure of N inside the chamber during the growing of these thin films, affects the stoichiometry of the TiN x deposited. The results obtained were that the different thin films change each one through TiN x (x = 0.88–1.33). The results were supported with XPS and EELS spectroscopy doing also an analysis of elemental ratio to show the stoichiometry and sub-stoichiometry obtained. This work concludes the adequate conditions for this experiment to obtain TiN as thin film by PLD at room temperature, supported with the results in the present work and the interpretation of the AES spectra even when Ti and N peaks overlap.
Keywords: AES; XPS; TiN; Thin films; PLD;
SIMS analysis of residual gas elements with a Cameca IMS-6f ion microprobe by Yu. Kudriavtsev; A. Villegas; A. Godines; R. Asomoza (3406-3412).
In this paper, we present experimental data for SIMS analysis of residual gas elements (RGEs) with a Cameca IMS-6f ion microprobe. We considered a simple experimental technique, which provides an effective separation of the secondary ions, sputtered from the bulk of a target, and from the molecules, adsorbed on the analyzed surface from the residual atmosphere. The technique needs the sputtering yield of one monolayer (ML) per second to be applied. The method improves (in more than one order of magnitude) the detection limit for RGEs in SIMS analysis, and simultaneously, provides information about the residual atmosphere at the sample surface and in the main chamber of the experimental instrument. The method provides a calibration method for an ion gauge, and can be used for SIMS analysis with a gas (O2) flooding.
Keywords: SIMS; Silicon; Residual atmosphere;
Near-edge X-ray absorption fine-structure studies of GaN under low-energy nitrogen ion bombardment by V.A. Coleman; M. Petravić; K.-J. Kim; B. Kim; G. Li (3413-3416).
The electronic structure of p-type GaN layers exposed to low-energy nitrogen ion bombardment was studied by near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy. It was found that ion bombardment lead to the creation of states lying below the nitrogen absorption edge which posses p-symmetry. These states are attributed to nitrogen interstitials with different local topologies created during ion bombardment. Furthermore, the NEXAFS spectra also shows the development of a strong π ∗ -resonance above the absorption edge with increasing incident nitrogen ion energy. This peak is attributed to the formation of molecular nitrogen at interstitial positions, arising from a build up of nitrogen ions on these sites.
Keywords: GaN; NEXAFS; Nitrogen ion bombardment;
Surface analysis for LiBq4 growing on ITO and CuPc film using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) by Ou Gu-ping; Gui Wen-ming; Jin Shi-chao; Zhang Fu-jia (3417-3427).
We have investigated the morphology and surface electron states of LiBq4 deposited on ITO and CuPc/ITO, using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The AFM observations indicate that LiBq4 can form a much more uniform film on CuPc than that on ITO. Furthermore, X-ray photoelectron spectroscopy (XPS) is utilized to further demonstrate the AFM results. From the analysis of XPS, we found that LiBq4 molecules have poor thermal stability, they are seriously oxidized during depositing; but when a CuPc layer is inserted between LiBq4 and ITO film, the oxidation and surface contamination of LiBq4 are significantly reduced. It is then concluded that the introduction of a CuPc buffer layer under the LiBq4 film can improve the film quality of LiBq4.The XPS results also testified the fact that no coordination bonds between N atoms and B atoms are formed in LiBq4 molecules, which make LiBq4 to be potential blue organic light-emitting material.
Keywords: Atomic force microscopy (AFM); X-ray photoelectron spectroscopy (XPS); Electron affinity;
Electron scattering mechanisms in indium–tin-oxide thin films prepared at the various process conditions by Ho-Chul Lee (3428-3435).
The carrier concentrations and mobilities of indium–tin-oxide (ITO) thin films by DC magnetron sputtering at the various process conditions were measured by means of the Hall technique. The relationship between the carrier concentration and mobility showed two distinct features: (i) roughly up to the carrier concentration of 9.0 × 1020/cm3, both the carrier concentration and mobility increased together; (ii) above the carrier concentration of 9.0 × 1020/cm3, the carrier mobility decreased as the carrier concentration further increased. The distinct behavior of the carrier concentration and mobility was due to the transition of the dominant electron scattering mechanism. ITO thin film with a low degree of crystallinity was governed by the grain boundary scattering. However, the ionized impurity scattering was dominant in ITO thin film with a high carrier concentration over 9.0 × 1020/cm3. The overall characterizations related to the carrier concentration and mobility were also performed using X-ray diffractometer, UV–vis–NIR spectrometer, scanning electron microscope, atomic force microscope.
Keywords: Indium–tin-oxide (ITO); DC magnetron sputtering; Hall measurement; Carrier concentration; Carrier mobility; Surface roughness; Scattering;
Transition of 3D to 2D growth modes of InAs grown on GaAs by Z.L. Miao; S.J. Chua; Y.W Zhang; S. Tripathy (3436-3440).
We report a method to grow thin strain-released InAs layer on GaAs (1 0 0) substrates by molecular beam epitaxy. We have shown that by controlling the growth parameters, a thin 2D InAs layer can be grown during initial stages, which eventually serves as a buffer layer to trap dislocations and epitaxial regrowth of InAs on this buffer results in high crystal quality. The size dependence of the InAs islands formed during initial stages with growth time has been studied by atomic force microscopy. With continuous short-time epitaxial growth during various stages, the InAs growth mode transfers from 3D to 2D. The introduction of dislocations into InAs epitaxial islands and their behavior during initial growth stage has been theoretically studied. The theoretical results are in remarkable agreement with the experimental results and shows that once the film is formed, the film strain is totally relaxed. The 200 nm thick InAs epilayer grown on this buffer shows a narrow X-ray diffraction peak. Such InAs strain-released buffer layer would be useful for regrowth of high In content based materials on top of it for electronics and optoelectronics device applications.
Keywords: A1. Low dimensional structures; A3. Molecular beam epitaxy; B2. Semiconducting III–V materials;
Spray-pyrolysis deposition of LaMnO3 and La1−x Ca x MnO3 thin films by R. Todorovska; N. Petrova; D. Todorovsky; St. Groudeva-Zotova (3441-3448).
Ethylene glycol solutions of La–Mn(II) and La–Ca–Mn(II) citric complexes has been used as a starting material for spray-pyrolysis deposition of LaMnO3 and La1−x Ca x MnO3 thin films on β-quartz, fused quartz, Si(0 0 1) and SrTiO3(1 0 0) substrates heated during the deposition at 380 °C. At suitable post-deposition heating conditions highly uniform films, 0.1–1 μm in thickness, with good crystal structure were obtained. Highly textured LaMnO3 films are obtained on SrTiO3(1 0 0) substrate. Interaction between the layer and Si-containing substrates is observed during the post-deposition heating in static air.
Keywords: Rare earths; Manganites; Thin layers; Spray-pyrolysis; Citric complexes;
Fabrication and electrical characterization of nanocrystalline ZnO/Si heterojunctions by Yang Zhang; Jin Xu; Bixia Lin; Zhuxi Fu; Sheng Zhong; Cihui Liu; Ziyu Zhang (3449-3453).
Nanocrystalline zinc oxide (nc-ZnO) films were prepared by a sol–gel process on p-type single-crystalline Si substrates to fabricate nc-ZnO/p-Si heterojunctions. The structure and morphology of ZnO films on Si substrates, which were analyzed by X-ray diffraction (XRD) spectroscopy and atomic force microscopy (AFM), showed that ZnO films consisted of 50–100 nm polycrystalline nanograins with hexagonal wurtzite structure. The electrical transport properties of the nc-ZnO/p-Si heterojunctions were investigated by temperature-dependent current–voltage (I–V) measurements and room temperature capacitance–voltage measurements. The temperature-dependent I–V characteristics revealed that the forward conduction was determined by multi-step tunneling current, and the activation energy of saturation current was about 0.26 eV. The 1/C 2–V plots indicated the junction was abrupt and the junction built-in potential was 1.49 V at room temperature.
Keywords: ZnO; Sol–gel; Nanostructure; Heterojunction; Tunneling;
Morphological and luminescent characteristics of GaN dots deposited on AlN by alternate supply of TMG and NH3 by Yu-Li Tsai; Jyh-Rong Gong; Tai-Yuan Lin; Hsia-Yu Lin; Yang-Fang Chen; Kun-Ming Lin (3454-3459).
GaN dots were deposited on AlN underlayers by alternate supply of trimethylgallium (TMG) and ammonia (NH3) in an inductively heated quartz reactor operated at atmospheric pressure. Various growth parameters including deposition temperature, TMG admittance and pulse time between TMG and NH3 exposures were proposed to investigate the influence of growth parameters on the size distribution of GaN dots. It appears that GaN dots with uniform size distribution can be achieved under certain growth conditions. Based on the study of atomic force microscopy (AFM), high deposition temperature was found to be in favor of forming large GaN dots with small dot density. Decrement of TMG flow rate or reduction in the number of growth cycle tends to enable the formation of GaN dots with small dot sizes. The results of room temperature (RT) cathodoluminescence (CL) measurements of the GaN dots exhibit an emission peak at 3.735 eV. A remarkable blue shift of GaN dot emission was observed by reduced temperature photoluminescence (PL) measurements.
Keywords: GaN dot; AFM; CL; PL;
Interpretation of initial stage of 3C-SiC growth on Si(1 0 0) using dimethylsilane by Yuzuru Narita; Masayuki Harashima; Kanji Yasui; Tadashi Akahane; Masasuke Takata (3460-3465).
The initial stage of cubic silicon carbide (3C-SiC) growth on a Si(0 0 1) surface using dimethylsilane (DMS) as a source gas was observed using scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEED). It was found that the dimer vacancies initially existing on the Si(0 0 1)-(2 × 1) surface were repaired by the Si atoms in DMS molecules, during the formation of the c(4 × 4) surface. From the STM measurement, nucleation of SiC was found to start when the Si surface was covered with the c(4 × 4) structure but before the appearance of SiC spots in the RHEED pattern. The growth mechanism of SiC islands was also discussed based on the results of RHEED, STM and temperature-programmed desorption (TPD).
Keywords: Dimethylsilane (DMS); Scanning tunneling microscopy (STM); Silicon carbide;
Morphological and textural characterization of functionalized particulate silica xerogels by Lazaro A. de Miranda; Nelcy D.S. Mohallem; Welington F. de Magalhães (3466-3474).
The functionalization of xerogels for use in chromatography and catalysis was carried out by solubilization of amorphous silica using a soxhlet extractor. Xerogels were prepared by sol–gel method using tetraethoxysilane, TEOS, ethanol, and water in a 1/3/10 molar ratio with HCl and HF as catalysts. The samples were prepared in monolithic form and dried at 70 °C and 550 °C for 1 h each. After functionalization, changes in textural and morphological characteristics of xerogels were investigated by means of nitrogen gas adsorption, positron annihilation lifetime spectroscopy (PALS), and scanning electron microscopy (SEM). As the analysis methods are based on different physical principles, the results are complementary, leading to a good knowledge of the texture of the samples studied.
Keywords: Xerogel; Positron; Gas adsorption;
Microstructure and anti-oxidation property of CrSi2–SiC coating for carbon/carbon composites by Fu Qian-Gang; Li He-Jun; Shi Xiao-Hong; Liao Xiao-Ling; Li Ke-Zhi; Huang Min (3475-3480).
To protect carbon/carbon (C/C) composites from oxidation, a new type of oxidation protective coating has been produced by a two-step pack cementation technique. XRD and SEM analysis show, the coating obtained by the first step pack cementation was a porous β-SiC structure, and a new phase of CrSi2 was generated in the porous SiC coating after heat-treatment according to the second step pack cementation process. Oxidation test shows that, the weight loss of the SiC coated C/C is up to 11.26% after 5 h oxidation in air at 1773 K, and the weight loss of the CrSi2–SiC coated C/C composites is only 4.15% after oxidation in air at 1773 K for 34 h. The oxidation of C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks in the coating.
Keywords: Carbon/carbon composites; Coating; Oxidation;
Investigation of surface cleaning procedure of InP:S (1 0 0) substrates by high resolution XPS by M. Adamiec; E. Talik; A. Gładki (3481-3487).
The angle resolved X-ray photoelectron spectroscopy measurements were used to monitor a level of contamination of the InP:S (1 0 0) substrates during the cleaning processes with deionized water and isopropanol. Some contaminations with carbon and oxygen were found for a broken under ultrahigh vacuum InP:S substrate, indicating the contamination of the crystal during the growth process. The substrates after cleaning with deionized water and isopropanol were contaminated with carbon, oxygen, nitrogen and silicon. Concentration of carbon decreases inwards the substrates while concentration of oxygen is enhanced even in the deeper layers for both processes. The nitrogen concentration is higher for the samples rinsed with water. Roughness of the surfaces is higher for the samples rinsed with water what indicated the AFM measurements.
Keywords: Indium-phosphide; Electron states; X-ray spectroscopy;
Chromium localization in plant tissues of Lycopersicum esculentum Mill using ICP-MS and ion microscopy (SIMS) by Pedro Antonio Mangabeira; Konstantin L. Gavrilov; Alex-Alan Furtado de Almeida; Arno Heeren Oliveira; Maria Isabel Severo; Tiago Santana Rosa; Delmira da Costa Silva; Lise Labejof; Françoise Escaig; Riccardo Levi-Setti; Marcelo Schramm Mielke; Florence Grenier Loustalot; Pierre Galle (3488-3501).
High-resolution imaging secondary ion mass spectrometry (HRI-SIMS) in combination with inductively coupled plasma mass spectrometry (ICP-MS) were utilised to determine specific sites of chromium concentration in tomato plant tissues (roots, stems and leaves). The tissues were obtained from plants grown for 2 months in hydroponic conditions with Cr added in a form chromium salt (CrCl3·6H2O) to concentrations of 25 and 50 mg/L. The chemical fixation procedure used permit to localize only insoluble or strongly bound Cr components in tomato plant tissue. In this work no quantitative SIMS analysis was made. HRI-SIMS analysis revealed that the transport of chromium is restricted to the vascular system of roots, stems and leaves. No Cr was detected in epidermis, palisade parenchyma and spongy parenchyma cells of the leaves. The SIMS-300 spectra obtained from the tissues confirm the HRI-SIMS observations. The roots, and especially walls of xylem vessels, were determined as the principal site of chromium accumulation in tomato plants.
Keywords: Ionic microscopy; Microanalyses; Heavy metal;
Effects of O2/Ar flow ratio on the alcohol sensitivity of tin oxide film by Hsiao-Ching Lee; Weng-Sing Hwang; Gwo-Bin Lee; Yang-Ming Lu (3502-3508).
The aim of this study is to find the effects of oxygen flow rate during manufacturing on the sensitivity of SnO2 (tin oxide) thin films to ethanol (C2H5OH). In this study, an RF sputtering process was employed to fabricate the SnO2 thin films. The SnO2 was deposited on gold electrode silicon microchips. A target composed of SnO2 doped with 1 at.% Li was used with a working pressure of 3 mTorr. The RF power was fixed at 150 W. The reaction gas was a mixture of argon and oxygen. The total flow rate was constant at 50 sccm with the O2/Ar ratio varying from 0.2 to 0.8. An annealing heat treatment was employed at 400 °C for 1 h to stabilize the properties of the films. The sensitivity of the film to ethanol was tested by placing the micro-reactor device on a hot plate, heated to 300 °C, and measuring the variation of electrical resistivity of the film with and without the presence of ethanol. The results show that an O2/Ar flow ratio of 0.2 produces films with the highest ethanol sensitivity. Before heat treating, the ethanol sensitivity was 126. After heat treating at 400 °C for 1 h, the sensitivity decreased to 104.
Keywords: Gas sensor; Ethanol; Tin oxide; Sensitivity;
Direct observation of room temperature magnetism in (In,Mn)As thin films by magnetic force microscopy by S.J. May; A.J. Blattner; D.P. Eam; B.W. Wessels (3509-3513).
Variable-temperature magnetic force microscopy (MFM) has been performed over the temperature range of 298–348 K on ferromagnetic (In,Mn)As thin films deposited by metal-organic vapor phase epitaxy (MOVPE). Ferromagnetic domains were observed with submicron resolution in both single and two phase (In,Mn)As films, persisting up to 328 K. Isolated cylindrical domains ranging from 100 to 350 nm in diameter with densities of 2–5 × 108 cm−2 were observed in phase pure films. Longer range magnetic order, in the form of ribbon-like domains up to 1 μm in length, are present in the regions between the cylindrical domains. Two phase (In,Mn)As films produced a well-resolved complex domain structure consisting of 180° parallel and antiparallel domains. Excellent agreement between the temperature dependence of the relative magnetization obtained by MFM and superconducting quantum interference device measurements was observed.
Keywords: Ferromagnetic semiconductors; Magnetic domains; Magnetic force microscopy;
Surface morphologies of anthracene single crystals grown from vapor phase by Sadaharu Jo; Hitoshi Yoshikawa; Akane Fujii; Mitsuru Takenaga (3514-3519).
The morphologies and lattice structures of anthracene single crystals grown from the vapor phase were investigated using optical microscopy, phase contrast microscopy, atomic force microscopy (AFM), and X-ray diffraction analysis. Common morphologies with hexagonal large planes were observed irrespective of crystal size. The observation of certain surface morphologies with a phase contrast microscopy revealed that the spiral steps originated from screw dislocations present on the (0 0 1) planes. Moreover, the center and edge of the (0 0 1) planes had large curvatures, similar to hills. Resultantly, quarter-monolayer (ML) steps were observed on the large and flat planes between both hills.
Keywords: Anthracene; Single crystal; Vapor growth; Morphology; Screw dislocation; Spiral step pattern; Quarter-ML step;
Synergistic inhibitive effect of tartarate and tungstate in preventing steel corrosion in aqueous media by B. Jabeera; S.M.A. Shibli; T.S. Anirudhan (3520-3524).
The inhibitive effect of tartarate was studied as a coinhibitor with tungstate in preventing carbon steel corrosion in aqueous solutions. Open circuit potential measurements, weight-loss measurements and polarization studies were conducted to understand the domains of corrosion and passivation. Tartarate ions, even at low concentration, showed excellent synergistic corrosion inhibition characteristics. A mixture of 500 ppm each of the inhibitors was found to be optimum inhibitor combination. This inhibitor combination showed inhibition efficiency as high as 98%. Tartarate in the synergistic inhibitor combination did not reveal any dominant role in shifting the surface potential, even though it showed substantial passivation effect. The present study explores and evaluates the synergistic combination as a potential inhibitor system in combating corrosion on carbon steel surface.
Keywords: Tartarate; Tungstate; Corrosion inhibitors; Steel corrosion;
Structure and electrical transport properties of bismuth thin films prepared by RF magnetron sputtering by Dong-Ho Kim; Sung-Hun Lee; Jong-Kuk Kim; Gun-Hwan Lee (3525-3531).
Bismuth thin films were prepared on glass substrates with RF magnetron sputtering and the effects of deposition temperature on surface morphology and their electrical transport properties were investigated. Grain growth of bismuth and the coalescence of grains were observed above 393 K with field emission secondary electron microscopy. Continuous thin films could not be obtained above 448 K because of the segregation of grains. Hall effect measurements showed that substrate heating yields the decrease of carrier density and the increase of mobility in exponential ways until 403 K. Resistivity of sputter deposited bismuth films has its minimum (about 0.7 × 10−3 Ω cm) in range of 403–433 K. Annealing of bismuth films deposited at room temperature was carried out in a radiation furnace with flowing hydrogen gas. The change of resistivity was not significant due to the cancellation of the decrease of carrier density and the increase of mobility. However, the abrupt change of electrical properties of film annealed above 523 K was observed, which is caused by the oxidation of bismuth layer.
Keywords: Bismuth; Thermoelectric thin film; Electrical transport properties; Sputtering;
Self-assembled monolayer growth on chemically modified polymer surfaces by S. Pimanpang; Pei-I. Wang; G.-C. Wang; T.-M. Lu (3532-3540).
We report a study of the self-assembled monolayer (SAM) growth of bis[3(triethoxysilane)propyl]tetrasulfide (Tetrasulfide) on low dielectric constant (low-k) aromatic hydrocarbon SiLK whose surface chemistry was modified using sulfuric acid, He plasma treatment, and N2 plasma treatment. X-ray photoelectron spectroscopy (XPS) spectra show that there is no detectable growth of Tetrasulfide SAM on untreated SiLK surfaces. After the SiLK surfaces have been treated with sulfuric acid, He plasma, or N2 plasma, the original chemically inert polymer surfaces are functionalized with polar groups resulting in a significant improvement of their wettability, which is confirmed by their reduction of water droplet contact angles. The introduction of polar functional groups thus facilitates the formation of Tetrasulfide SAM on the polymer surfaces. Atomic force microscopy (AFM) analysis shows an insignificant change in the surface morphology after the growth of Tetrasulfide SAM on the chemically modified SiLK surfaces. Quantitative XPS analysis also showed that Tetrasulfide SAM growth is more prominent on He and N2 plasma treated surfaces than those treated by sulfuric acid.
Keywords: SiLK; Self-assembled monolayer; Plasma treatment; AFM; XPS; Contact angle;
Investigation of laminar plasma remelting/cladding processing by Wei Ma; Qunxing Fei; Wenxia Pan; Chengkang Wu (3541-3546).
Investigation of remelting and cladding processing with laminar plasma jets on several metals has been conducted looking for possible development of a new surface modification technique. The remelting tests illustrated that the new method could evidently improve the material microstructure and properties of cast iron. The cladding was done with Al2O3 ceramic powder on stainless steel. The energy dispersive spectra (EDS) analysis was used to determine the distribution of the major cladding element in the plasma-processed layers, for which the microstructure observations and hardness measurements were also performed.
Keywords: Laminar plasma jets; Remelting; Cladding; Microstructure;
Production and characterization of polymer nanocomposite with aligned single wall carbon nanotubes by Wei Chen; Xiaoming Tao (3547-3552).
We reported a simple method to fabricate polymer nanocomposites with single-walled carbon nanotubes (SWNTs) having exceptional alignment and improved mechanical properties. The composite films were fabricated by casting a suspension of single walled carbon nanotubes in a solution of thermoplastic polyurethane and tetrahydrofuran. The orientation as well as dispersion of nanotubes was determined by scanning electron microscopy, transmission electron microscopy and polarized Raman spectroscopy. The macroscopic alignment probably results from solvent–polymer interaction induced orientation of soft segment chain during swelling and moisture curing. The tensile behavior of the aligned nanotube composite film was also studied. At a 0.5 wt.% nanotube loading, a 1.9-fold increase in Young's modulus was achieved.
Keywords: Carbon nanotube; Polymer; Nanocomposite;
Quantitative evaluation about property of thin-film formation by Huawei Chen; Ichiro Hagiwara; Tian Huang; Dawei Zhang (3553-3560).
Chemical vapor deposition (CVD) is gradually emphasized as one promising method for nanomaterial formation. Such growth mechanism has been mainly investigated on basis of experiment. Due to large cost of the equipment of experiment and low level of current measurement, the comprehension about authentic effect of formation condition on properties of nanomaterial is limited in qualitative manner. Three quantitative items: flatness of primary deposition, adhesion between cluster and substrate, and degree of epitaxial growth were proposed to evaluate the property of thin film. In this simulation, three different cluster sizes of 203, 653, 1563 atoms with different velocities (0, 10, 100, 1000, 3000 m/s) were deposited on a Cu(0 0 1) substrate whose temperatures were set between 300 and 1000 K. Within one velocity range, not only the speed of epitaxial growth and adhesion between thin film and substrate were enhanced, but also the degree of epitaxy increased and the shape of thin film became more flat with velocity increasing. Moreover, the epitaxial growth became well as the temperature of substrate was raised within a certain range, and the degree of epitaxy of small cluster was larger than larger cluster. The results indicated that the property of thin film could be controlled if the effect of situations of process was made clear.
Keywords: Molecular dynamics; Computer simulation; Epitaxy; Thin film; CVD;
Electrodeposition of Pb-free Sn alloys in pulsed current by B. Neveu; F. Lallemand; G. Poupon; Z. Mekhalif (3561-3573).
A pulsed electrodeposition method is applied to the preparation of Pb-free Sn alloys solder bumps for flip-chip bonding with the aid of a photolithography. Sn–Ag alloy films with near eutectic compositions (Sn–3.5% Ag) were obtained using a pyrophosphate–iodide plating baths regardless under direct or pulsed current. The composition and the morphology of electrodeposits were examinated by SEM and X-ray photoelectron spectroscopy (XPS). The main results revealed that the organic additives affect the electrochemical reduction of tin–silver and the direct consequence on making Sn–Ag alloy is a decreased deposition rate. However, the addition of additives in the plating bath suppressed the dendritic tin–silver growth by adsorption on the deposited surface. Pulsed electrodeposition is shown to be an interesting approach to elaborate bumps with smooth and homogeneous surfaces.
Keywords: Sn–Ag eutectic alloy; Organic additives; Pulse plating; Electroplating;
Preparation of poly(2-chloroaniline) membrane and plasma surface modification by E. Kır; L. Oksuz; S. Helhel (3574-3579).
P2ClAn membranes were obtained from chemically synthesized poly(2-chloroaniline) (P2ClAn) by casting method. These membranes were cast from dimethyl formamide (DMF) and were in the undoped state. P2ClAn membranes were characterized by Fourier infrared spectroscopy and scanning electron microscopy. Measurements of water content capacity, membrane thickness and ion-exchange capacity of the cast membranes were carried out. P2ClAn membranes were treated by electron cylotron resonance (ECR) plasma for surface modification. Plasma treatment has been successfully utilized for improving the surface properties of P2ClAn membranes such as increasing pore diameters and number of pores for better anion or molecule transportation.
Keywords: Poly(2-chloroaniline) membranes; Preparation; Characterization; Plasma treatment;
Novel transparent Yb-based cathodes for top-emitting organic light emitting devices with high performance by G.L. Ma; G.Z. Ran; A.G. Xu; Y.P. Qiao; W.Q. Zhao; B.R. Zhang; S.K. Wu; G.G. Qin (3580-3584).
We have studied three kinds of transparent low-work-function Yb-based cathodes for the top-emitting organic light emitting devices (TEOLEDs) with a structure of ITO/NPB/Alq3/cathodes and compared them with each other. For the Yb/Au cathodes, a series of Yb layers with various thicknesses have been tested and it is found that the Yb layer with a thickness of 4 nm is the optimum one. The Yb:Au (19 nm) and Yb:Ag (19 nm) co-evaporation cathodes possess very high transmittance but relative poor electron injection; whilst the Yb (4 nm)/Au (15 nm) cathode possess a little lower transmittance but much improved electron injection and the TEOLED with this cathode has the highest power efficiency among the TEOLEDs with the three kinds of Yb-based cathodes mentioned above.
Keywords: OLED; Top-emitting; Transparent cathode;
Room temperature electrodeposition and characterization of bismuth ferric oxide (BFO) thin films from aqueous nitrate bath by T.P. Gujar; V.R. Shinde; S.S. Kulkarni; H.M. Pathan; C.D. Lokhande (3585-3590).
Bismuth ferric oxide (BFO) thin films were prepared on fluorine doped tin oxide (FTO) coated glass substrates using electrodeposition method from aqueous nitrate bath at room temperature. The various preparative parameters, such as bath composition, current density, deposition time, etc were optimized to get good quality BFO thin films. The structural, surface morphological, optical and dielectrical properties of the films were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption and dielectric measurement techniques. The results show that electrodeposition method allows to synthesis BFO films. The films are free from pinholes and cracks. The magnitudes of dielectric constant and loss tangent showed inverse frequency dependence.
Keywords: Bismuth ferric oxide; Thin films; Electrodeposition; Preparation and characterization;
Mechanical properties and wear and corrosion resistance of electrodeposited Ni–Co/SiC nanocomposite coating by Lei Shi; Chufeng Sun; Ping Gao; Feng Zhou; Weimin Liu (3591-3599).
Ni–Co/SiC nanocomposite coatings with various contents of SiC nano-particulates were prepared by electrodeposition in a Ni–Co plating bath containing SiC nano-particulates to be co-deposited. The influences of the nanoparticulates concentration, current density, stirring rate and temperature of the plating bath on the composition of the coatings were investigated. The shape and size of the SiC nano-particulates were observed and determined using a transmission electron microscope. The polarization behavior of the composite plating bath was examined on a PAR-273A potentiostat/galvanostat device. The wear behavior of the Ni–Co/SiC nanocomposite coatings was evaluated on a ball-on-disk UMT-2MT test rig. The worn surface morphologies of the Ni–Co/SiC nanocomposite coatings were observed using a scanning electron microscope. The corrosion behavior of the nanocomposite coatings was evaluated by charting the Tafel curves of the solution of 0.5 mol L−1 NaCl at room temperature. It was found that the cathodic polarization potential of the composite electrolyte increased with increasing SiC concentration in the plating bath. The microhardness and wear and corrosion resistance of the nanocomposite coatings also increased with increasing content of the nano-SiC in the plating bath, and the morphologies of the nanocomposite coatings varied with varying SiC concentration in the plating bath as well. Moreover, the co-deposited SiC nano-particulates were uniformly distributed in the Ni–Co matrix and contributed to greatly increase the microhardness and wear resistance of the Ni–Co alloy coating.
Keywords: Electrodepostion; Ni–Co alloy coating; SiC nano-particulates; Nanocomposite coating; Wear behavior;
The photocatalytic application and regeneration of anatase thin films with embedded commercial TiO2 particles deposited on glass microrods by Jorge Medina-Valtierra; Josafat García-Servín; Claudio Frausto-Reyes; Sergio Calixto (3600-3608).
Anatase thin films (<200 nm in thickness) embedding Degussa P25 TiO2 were prepared by sol–gel method. TiO2-anatase thin films were deposited on a fiberglass substrate and then ground to obtain glass microrods containing the composite films. The film structure was characterized using Raman spectroscopy, atomic absorption and UV–vis spectrophotometry, and atomic force microscopy. The photocatalytic activity of the composite films, calcined at 450 °C, and the regeneration of the activity under the same experimental conditions, were assessed using gas chromatography to study the photodegradation of phenol, an industrial pollutant, in water under 365 nm irradiation. The film with 15.0 wt.% of P25 TiO2 was found to be more photoactive (54 ppm of degraded phenol at 6 h of illumination) than the other ones.
Keywords: Anatase films; Degussa P25 TiO2; Photocatalysis; Phenol degradation; Photocatalyst regeneration;
Characterization of bicrystalline epitaxial LaNiO3 films fabricated on MgO (1 0 0) substrates by pulsed laser deposition by Liang Zheng; Jun Zhu; Ying Zhang; Shu Wen Jiang; Yan Rong Li; Xian HuaWei; Jin Long Li (3609-3615).
A series of metallic LaNiO3 (LNO) thin films were deposited on MgO (1 0 0) substrates by pulsed laser deposition (PLD) under the oxygen pressure of 20 Pa at different substrate temperatures from 450 to 750 °C. X-ray diffraction (XRD) was used to characterize the crystal structure of LNO films. θ–2θ scans of XRD indicate that LNO film deposited at a substrate temperature of 700 °C has a high orientation of (l l 0). At other substrate temperatures, the LNO films have mixed phases of (l l 0) and (l 0 0). Furthermore, pole figure measurements show that LNO thin films, with the bicrystalline structure, were epitaxially deposited on MgO (1 0 0) substrates in the mode of LNO (1 1 0)//MgO (1 0 0) at 700 °C. Reflection high-energy electric diffraction (RHEED) and atomic force microscopy (AFM) were also performed to investigate the microstructure of LNO films with the high (l l 0) orientation. RHEED patterns clearly confirm this epitaxial relationship. An atomically smooth surface of LNO films at 700 °C was obtained. In addition, bicrystalline epitaxial LNO films, fabricated at 700 °C, present a excellent conductivity with a lower electrical resistivity of 300 μ Ω cm. Thus, the obtained results indicate that bicystalline epitaxial LNO films could serve as a promising candidate of electrode materials for the fabrication of ferroelectric or dielectric films.
Keywords: Bicrystalline epitaxy; X-ray diffraction; Pole figure; LaNiO3; MgO;
Windowless argon excimer source for surface modification by Christian Elsner; Martin Lenk; Lutz Prager; Reiner Mehnert (3616-3624).
The article describes applications of a novel windowless argon excimer source for surface modification. Experimental results on etching of polymeric surfaces, degradation of organic surface residues, surface activation and modification of gas permeability and selectivity of polymeric membranes are presented. Moreover, radical formation from the excimer source and surface curing of liquid acrylates are examined. Typical treatment times are in the range of minutes for photolytic decomposition effects and seconds for UV curing effects. The surface modification effects induced by the argon excimer source were analysed by XPS, ESR, IR-spectroscopy, white light reflection spectroscopy, scanning electron microscopy, micro-hardness and permeation measurements.
Keywords: Argon excimer lamp; Coating; Adhesion promoter; Barrier discharge; Plasma treatment; Atmospheric pressure plasma;
Kinetics of residual gas adsorption on Ge(1 1 1) surface in low-energy electron backscattering by O.B. Shpenik; T.Yu. Popik; V.M. Feyer; Yu.V. Popik (3625-3631).
Low-energy (0.4–1.2 eV) electron backscattering is applied for the investigation of kinetics of residual gas adsorption effect on the concentration and energy positions of surface electron states of Ge(1 1 1) surface. Chemosorption of residual gas molecules on Ge(1 1 1) at P ∼ 10−7 Pa and room temperature is shown to be most active during the first 48 h. Low concentration of dangling valence bonds on the reconstructed Ge(1 1 1) (2 × 8) surface is shown to determine its low activity to chemosorption.
Keywords: Germanium; Electron energy loss spectroscopy (EELS); Surface electronic phenomena (work function; surface potential; surface states, etc.);
X-ray photoelectron study of Sn1−x Mn x Te semimagnetic semiconductors by R.J. Iwanowski; M.H. Heinonen; W. Paszkowicz; R. Minikaev; T. Story; B. Witkowska (3632-3641).
X-ray photoelectron (XPS) studies of core-levels in Sn1−x Mn x Te (x < 0.1) semimagnetic semiconductors have been performed. The spectra were acquired under UHV conditions from the clean (as-cleaved or in-situ scraped) crystal surface. The single-phase NaCl structure of the alloys studied was verified by X-ray diffraction (XRD). The structure of Sn 3d and Te 3d core-levels in SnMnTe was found fully consistent with that of SnTe. Remarkable qualitative similarity of the Mn 2p spectrum of Sn1−x Mn x Te (x = 0.09) with the case of zinc-blende MnTe [R.J. Iwanowski, M.H. Heinonen, E. Janik, Chem. Phys. Lett. 387 (2004) 110] has been shown: (1) the same binding energies (BEs) of the main contributions to the Mn 2p3/2 line, related to Mn2+ state of the bulk Mn―Te bond; (2) occurrence of low BE component in the Mn 2p spectrum, indicative of clean-surface species containing reduced-valence Mn ions (i.e. Mn q+, where 0 < q < 2); (3) strong satellites of the 2p3/2 (Mn2+ related) parent lines. In SnMnTe, the highest intensity ratio of the satellite to main peak (ever reported for Mn 2p photoelectron spectrum) was revealed; this was interpreted in terms of the so-called charge-transfer model.
Keywords: X-ray photoelectron spectroscopy; Single crystal surface; Tin manganese telluride; Manganese valency; Diluted magnetic semiconductors;
Study on anti-emission materials for non-emitting grid applications in microwave power tubes by J. Jiang; B.Y. Jiang; C.X. Ren; F.M. Zhang; T. Feng; X. Wang; X.H. Liu; S.C. Zou (3642-3646).
Hafnium and platinum were deposited onto molybdenum grids by ion-beam assisted deposition method. Electron-emission characteristics from molybdenum grids with Hf and Pt films, which were contaminated by active electron-emission substances (Ba, BaO) of the cathode, were measured using analogous diode method. The surfaces of grids were analyzed by X-ray diffraction. The results revealed that the reaction between BaO and Hf formed BaHfO3 compound, which greatly reduced the accumulation of BaO on the surface and accordingly decreased grid emission. In contrast, Ba were formed by the decomposition of BaO on the surface of Pt film under high temperature and re-evaporated from its surface, which reduced the active electron-emission substances on the surface of the grid and effectively restrained grid emission. Their mechanisms for grid-emission suppression are discussed and a good method to develop new grid-coating materials is suggested.
Keywords: Electron emission; Ion beam assisted deposition; Platinum; Hafnium;
Vibrational EELS and DFT study of propionic acid and pyruvic acid on Ni(1 0 0): Effects of keto group substitution on room-temperature adsorption and thermal chemistry by X. Yang; Z.H. He; X.J. Zhou; S.H. Xu; K.T. Leung (3647-3657).
The room-temperature adsorption and thermally induced processes of propionic acid and pyruvic acid on Ni(1 0 0) have been investigated by electron energy loss spectroscopy (EELS). Computational vibrational analysis of the optimized bidentate structures for acid–Ni model complexes (involving the organic acid and a Ni atom) has been performed by using the two-layer ONIOM method with the Density Functional Theory and used to interpret the vibrational EELS data. Dehydrogenation of the hydroxyl group is found to result in bonding of the carboxylate group in the propionate and pyruvate adspecies to either a single Ni surface atom in a bidentate configuration or two neighbouring Ni atoms in a bridge configuration. Given the similarities in the total energies and related vibrational frequencies obtained by the calculations in the case of pyruvate adspecies, it is difficult to differentiate the alternate adsorption structure, in which the keto O and hydroxyl O atoms are bonded to a Ni atom in a five-member chelate ring configuration. Furthermore, temperature-dependent EELS studies show that both the propionate and pyruvate adspecies could decompose upon annealing to above 400 K and further dissociate to CO adspecies above 550 K and to C and/or O above 600 K.
Keywords: Electron energy loss spectroscopy; Density Functional Theory; Propionic acid; Pyruvic acid; Ni(1 0 0);
Inhibition of metal dusting of Alloy 800H by laser surface melting by K.T. Voisey; Z. Liu; F.H. Stott (3658-3666).
Metal dusting is a catastrophic carburisation phenomenon that occurs at temperatures of 450–850 °C in atmospheres of high carbon activity. The resistance of alloys to corrosion, including metal dusting, relies on the formation of a dense, adherent oxide layer that separates the alloy from the corrosive environment. For such an oxide layer to be protective, it must achieve full surface coverage, be crack-free and be established before significant material degradation has occurred. Formation of a protective oxide scale can be enhanced by increasing the population of rapid diffusion paths for the protective elements (e.g. Cr and Al) to reach the alloy surface.In this work, laser surface melting has been used to improve the metal dusting resistance of Alloy 800H by creating a rapid solidification microstructure and, thereby, increasing the density of rapid diffusion paths. Oxidation during laser processing has been found to be detrimental to metal dusting resistance. However, it has been demonstrated that the resulting oxide can be removed without compromising metal dusting resistance.Results of exposure to a metal dusting atmosphere (20% H2 and 80% CO at 650 °C) are presented. Samples have been examined in plan and cross-section using optical and scanning electron microscopy (SEM). Selected samples were also examined by electron probe microanalysis (EPMA) and X-ray diffraction (XRD).
Keywords: Metal dusting; Laser surface melting; Laser-induced oxidation;
The inhibition effect of some amino acids towards Pb–Sb–Se–As alloy corrosion in sulfuric acid solution by Z. Ghasemi; A. Tizpar (3667-3672).
The inhibition effect of three amino acids towards the corrosion of Pb–Sb–Se–As alloy in 1.28 s.g. H2SO4 solution was investigated with linear polarization and weight loss measurements methods. The results drawn from two different techniques are comparable. The used amino acids were tryptophane, proline and methionine. The effect of inhibitor concentration and temperature against inhibitor action was investigated. It was found that these inhibitors act as good inhibitors for the corrosion of lead alloy in H2SO4 solution. Increasing inhibitor concentration increases the inhibition efficiency. It was found that adsorption of used amino acids on lead alloy surface follows Langmuir isotherm.
Keywords: Corrosion; Lead alloys; Inhibitor; Amino acids;
Design parameters for measurements of local catalytic activity on surfaces by M. Johansson; T. Johannessen; J. Hoffmann Jørgensen; I. Chorkendorff (3673-3685).
Computational fluid dynamics in combination with experiments is used to characterize a gas sampling device for measurements of the local catalytic activity on surfaces. The device basically consists of a quartz capillary mounted concentrically inside an aluminum tube. Reactant gas is blown toward the catalytic surface through the annulus between the tubes, and the gas is sampled close to the surface by the capillary. The influence of various design parameters on the lateral resolution and sensitivity of the measurements is investigated. It is found that the outer diameter of the annulus sets the upper limit for the lateral resolution of the measurement, and that a flow rate of the order of 240 (ml/min) n is sufficient to achieve this resolution. The sensitivity is reasonable also with high flow rates, due to the presence of a pocket of stagnant gas under the tip of the capillary. Furthermore, the limits of the range in reaction rate, which can be studied are estimated.
Keywords: Heterogeneous catalysis; Local gas sampling; Local reaction rate;
Single-atom coherent field electron emitters for practical application to electron microscopy: Buildup controllability, self-repairing function and demountable characteristic by E. Rokuta; T. Itagaki; T. Ishikawa; B.-L. Cho; H.-S. Kuo; T.T. Tsong; C. Oshima (3686-3691).
We have fabricated single-atom field emission (FE) tips by annealing Rh-deposited W tips at 900 K, and the FE characteristics were investigated. Due to the formation of the nanotips, the electron beams were confined in a semi-cone angle of 3°, an indication quite different from the conventional FE beams. In repairing-function test where the FE nanotips were intentionally destroyed beforehand, they recovered the peculiar FE characteristics by means of feasible low temperature annealing. Finally, we found that the present nanotips equipped the capability of recovering the unique FE properties even after an exposure to the air. These characteristics are significantly relevant to the practical applications to electron-optics instruments.
Keywords: Filed emission; Nanotip; Emountablity; Self-repairing functions;
Temperature-dependent carbon incorporation into the Si1−y C y film during gas-source molecular beam epitaxy using monomethylsilane by A. Konno; K. Senthil; T. Murata; M. Suemitsu (3692-3696).
Coverage and adsorption state of hydrogen atoms on the growing surface of Si1−y C y film using monomethylsilane has been investigated by using temperature-programmed desorption (TPD) and multiple-internal-reflection Fourier-transform infrared spectroscopy (MIR-FT-IR). The surface hydrogen coverage decreases with the growth temperature T g until it disappears at 800 °C. All the H2-TPD spectra are well resolved into six SiH-related and one CH n -related hydrogen desorption peaks. The SiH-related FT-IR peak showed a blue shift with increasing T g, which, in conjunction with the TPD, is related to enhanced C incorporation at backbonds of SiH.
Keywords: SiC; Monomethylsilane; TPD; MIR-FT-IR; Surface hydrogen; Carbon incorporation;
The influence of implanted yttrium on the cyclic oxidation behaviour of 304 stainless steel by F. Riffard; H. Buscail; E. Caudron; R. Cueff; C. Issartel; S. Perrier (3697-3706).
High-temperature alloys are frequently used in power plants, gasification systems, petrochemical industry, combustion processes and in aerospace applications. Depending on the application, materials are subjected to corrosive atmospheres and thermal cycling. In the present work, thermal cycling was carried out in order to study the influence of implanted yttrium on the oxide scale adherence on 304 steel specimens oxidised in air at 1273 K. In situ X-ray diffraction indicates that the oxides formed at 1273 K are different on blank specimens compared to implanted specimens. Glancing angle XRD allows to analyse the oxide scale composition after cooling to room temperature.Experimental results show that yttrium implantation at a nominal dose of 1017 ions cm−2 does not improve significantly the cyclic oxidation behaviour of the austenitic AISI 304 steel. However, it appears that yttrium implantation remarkably enhance the oxidation resistance during isothermal oxidation. It reduces the transient oxidation stage and the parabolic oxidation rate constant by one order of magnitude.
Keywords: Stainless steel; Ion implantation; In situ X-ray diffraction; High temperature; Oxidation; Yttrium;
Copper sulfide coated polysulfone films by M.H. Kunita; A.W. Rinaldi; E.M. Girotto; E. Radovanovic; E.C. Muniz; A.F. Rubira (3707-3713).
The modification of polysulfone surface was used to obtain effective interactions between an organic polymeric surface and an inorganic specie. A previous treatment of the polymer surface with modifiers is required in order to provide adherence. Our objective was the synthesis and the surface characterization of copper sulfide coated polysulfone (CuS–PSf) films. SEM micrographs showed a homogeneous distribution of copper sulfide, which contributes to increasing electrical conductivity. X-ray analysis showed a decrease in copper sulfide particles (covellite porcelain) when compared with other polymeric composites prepared under similar conditions. The measured surface conductivity of the CuS–PSf films was higher than those of other similar systems, ca. 800 S cm−1.
Keywords: Copper sulfide; Polysulfone; 4,4′-Oxidianiline; Composites; Electrical conductivity;
Adhesion studies of latex film surfaces on the meso- and nanoscale by Attila Oláh; Mark A. Hempenius; Shan Zou; G. Julius Vancso (3714-3728).
In this paper the effects of surface roughness and annealing temperature (T) of latex coating films on adhesion are discussed for the different stages of the film formation process. The surface free energy of latex films was assessed in terms of practical work of adhesion (W) (or adherence) using a custom-built adhesion-testing device (ATD), atomic force microscopy (AFM), and contact angle measurements. For preannealed latex films surface roughness averages (R a) were determined from AFM height images and were related to the values of W obtained from ATD measurements at room temperature. The results obtained using these tests exhibiting surface behavior on different length scales indicate a dependence of the measured adhesion on surface roughness and temperature, as well as on the length scale of the measurements.First preannealed samples were studied, which were obtained by heat treatment above the respective glass transition temperatures (T g). Increasing the temperature of preannealing resulted in a decrease of the adherence observed in ATD experiments at room temperature. However, on the nanoscale, using AFM, no significant variation of the adherence was observed. This observation can be explained by roughness arguments. Preannealing decreases roughness which results in lower adherence values measured by ATD while for essentially single asperity AFM experiments roughness has an insignificant effect. Specimens were also annealed over a constant period of time (90 min) at different temperatures. At the end of the heat treatment, adhesion was measured at the treatment temperature by ATD. The amplified effect of temperature observed in this case on adherence is attributed to the combination of roughness decrease and increasing test temperature. In a third set of experiments completely annealed samples were studied by ATD as well as by AFM as a function of temperature. With increasing T values ATD showed a decrease in adherence, which is attributed to a decreasing surface free energy of the annealed films at elevated T values. AFM, on the other hand, showed an opposite trend which is assigned to increasing penetration of the tip into the tip/wetting polymer samples versus increasing temperature. Finally, annealing isotherms as a function of time were investigated by ATD in situ at different temperatures. This last set of experiments allowed us to optimize annealing time and temperature to achieve complete curing.
Keywords: JKR contact mechanics; Core-shell latex; Thermal annealing; Atomic force microscopy; Adhesion;
Effect of N2 ion flux on the photocatalysis of nitrogen-doped titanium oxide films by electron-beam evaporation by Tien-Syh Yang; Min-Chi Yang; Ching-Bin Shiu; Wen-Ku Chang; Ming-Show Wong (3729-3736).
Nitrogen-doped titanium oxide (TiO x N y ) films were prepared with ion-assisted electron-beam evaporation. The nitrogen (N) incorporated in the film is influenced by the N2 flux modulated by the N2 flow rate through an ion gun. The TiO x N y films have the absorption edge of TiO2 red-shifted to 500 nm and exhibit visible light-induced photocatalytic properties in the surface hydrophilicity and the degradation of methylene blue. The structures and states of nitrogen in the films are investigated by X-ray diffraction patterns (XRD), and X-ray photoelectron spectroscopy (XPS) and related to their visible light-induced photocatalytic properties. The results indicate that the substitutional N in anatase TiO2 can induce visible light photocatalysis. The substitutional N is readily doped by the energetic nitrogen ions from the ion gun. The best photocatalytic activity is obtained at the largest N loading about 5.6 at.%, corresponding to the most substitutional N in anatase TiO2. The film exhibits the degradation of methylene blue with a rate-constant (k) about 0.065 h−1 and retaining 7° water contact angle on the surface under visible light illumination.
Keywords: Titanium oxide; Nitrogen-doped titanium oxide; Photocatalysis; Visible light photocatalyst; Electron-beam evaporation; Nanostructure;
Effect of [Cu]/[In] ratio on properties of CuInS2 thin films prepared by successive ionic layer absorption and reaction method by Yong Shi; Zhengguo Jin; Chunyan Li; Hesong An; Jijun Qiu (3737-3743).
CuInS2 ternary films were prepared by a soft solution processing, i.e. successive ionic layer absorption and reaction (SILAR) method. The films were deposited on glass substrates at room temperature and heat-treated under Ar atmosphere at 500 °C for 1 h. CuCl2 and InCl3 mixed solutions with different ionic ratios ([Cu]/[In]) were used as cation precursor and Na2S as the anion precursor. The effect of the [Cu]/[In] ratio in precursor solution on the structural, chemical stoichiometry, topographical, optical and electrical properties of CuInS2 thin films was investigated. XPS results demonstrated that stoichiometric CuInS2 film can be obtained by adjusting [Cu]/[In] ratios in solution. Chalcopyrite structure of the film was confirmed by XRD analysis. The near stoichiometric CuInS2 film has the optical band gap E g of 1.45 and resistivity decreased with increase of [Cu]/[In] ratios.
Keywords: CuInS2; Thin films; SILAR; [Cu]/[In] ratio;
Wetting behavior of magnesite and dolomite surfaces by Nermin Gence (3744-3750).
Magnesite and dolomite are salt-type minerals that show similar chemical composition and flotation behavior due to same crystal structure, and sparingly soluble nature. The surface properties of minerals play a major role in determining their separation from each other in processes such as flotation. During flotation process, selectivity problem arises between magnesite and associated gangue minerals such as dolomite. There is a close relationship between floatability of minerals and their contact angles. Therefore, surface hydrophobicity of magnesite and dolomite minerals was investigated by contact angle measurements in the absence and presence of flotation reagents.Magnesite and dolomite show hydrophilic properties and they have got a small contact angle (magnesite ∼10.4° and dolomite ∼6.6°) in distilled water in the absence of any surfactant. The contact angle values at the magnesite and dolomite surfaces remained at 9.7°–10.9° in the presence of petroleum sulphonates (R825 and R840) while sodium oleate affected hydrophobicity of magnesite, and the contact angle value increased up to 79°. The contact angle value of 39° at dolomite surface was obtained in the solution of sodium oleate, respectively.
Keywords: Wetting; Magnesite; Dolomite; Contact angle; Sodium Oleate; Sodium silicate;
Extent of coverage of surfaces treated with hydrophobizing microemulsions: A mass spectrometry and contact angle study by Andras Nagy; Joseph P. Kennedy; Ping Wang; Chrys Wesdemiotis; Scott D. Hanton (3751-3759).
Glass surfaces were treated with various hydrophobizing microemulsions (HME) containing mineral seal oil or polyisobutylene as hydrophobes emulsified by dimethyl dicoco ammonium chloride (i.e. mimicking commercial car wash practices) and characterized by mass spectrometry (MS) and contact angle measurements. The cationic emulsifier mediates the anchoring of hydrophobes to the polar glass surface. It is demonstrated that by the use of even very low (0.3–3.0 w%) HME concentrations the surfaces become hydrophobic and repel water even after numerous (∼20) rinsing cycles. According to MS evidence, however, the surfaces are not fully saturated with hydrophobes and the unprotected areas remain vulnerable to environmental damage.
Keywords: Surface protection; Hydrophobizing microemulsions; Surface analysis; Secondary ion mass spectrometry;
Analysis of prosthetic knee wear debris extracted from synovial fluid by N. Stojilovic; J.D. Ehrman; E.T. Bender; J.C. Tokash; R.D. Ramsier; M.W. Kovacik (3760-3766).
We report on the use of X-ray photoelectron spectroscopy and scanning electron microscopy equipped with energy dispersive spectroscopy to investigate the metallic content of wear debris from prosthetic knees. Synovial fluid aspirated from patients with prosthetic knees was centrifuged, rinsed and dried, resulting in small deposits of wear debris. We identify the presence and composition of metal wear debris from the femoral, tibial, and in some cases the patellar prosthetic components. We also demonstrate the inhomogeneous size, shape, and distribution of the wear particles, and both lateral and vertical elemental inhomogeneity. This points to the necessity of using a combination of techniques for studying such wear debris. The ability to detect the presence of certain metals within the synovial fluid of patients, even when surgical inspection did not identify wear of specific components, may have far reaching implications in the biomedical and prosthetics communities.
Keywords: Knee arthroplasty; Wear debris; XPS; SEM; EDS; Ti–6Al–4V; Co–Cr–Mo;
Sorption of selenium(IV) and selenium(VI) onto magnetite by M. Martínez; J. Giménez; J. de Pablo; M. Rovira; L. Duro (3767-3773).
In this work, we have studied the sorption of selenium (79Se is one of the main radionuclides in a spent nuclear fuel repository) on magnetite (Fe3O4), a mineral present in the near-field of a nuclear waste repository that might represent an important retardation factor for the mobility of many radionuclides.The sorption of both Se(IV) and Se(VI) onto magnetite has been fitted by a non-competitive Langmuir isotherm with Γ max = (3.13 ± 0.07) × 10−6 mol m−2 and K L = (1.19 ± 0.07) × 106 dm3 mol−1 for Se(IV) and Γ max = (3.5 ± 0.2) × 10−6 mol m−2 and K L = (3.0 ± 0.1) × 105 dm3 mol−1 for Se(VI).The variation of the sorption of selenium with pH has been modeled using the Triple Layer Surface Complexation Model and the equilibrium constants between selenium and magnetite have been obtained using the FITEQL program. For the case of Se(IV), the best fitting has been obtained using two inner-sphere complexes, FeOHSeO3 2− and FeHSeO3, while for Se(VI), the best fitting has been obtained considering only an outer-sphere complex, FeOH2 + ―SeO4 2−.The surface complexation reactions derived in this work are in agreement with those stated by other authors for sorption of Se(IV) and Se(VI) on hydrous iron oxides.
Keywords: Sorption; Magnetite; Spent nuclear fuel; Langmuir isotherm; Surface complexation;
Polymerization of butadiene on nanoparticles’ surfaces and formation of metal/polymer nanocomposites by V. Abdelsayed; Y. Ibrahim; M.S. El-Shall; S. Deevi (3774-3782).
In this paper, we demonstrate that laser vaporization of metals in the presence of a small concentration of butadiene vapor leads to the polymerization of butadiene and incorporation of the metal nanoparticles within the polymer matrix. The metal nanocomposites are characterized by electron microscopy, X-ray diffraction and EDX. The results from high pressure mass spectrometry indicate that multiple additions of butadiene molecules on the metal cations Fe+, Ni+ and Pt+, generated by laser vaporization, take place at room temperature thus providing an efficient means of initiating further polymerization reactions. The Pt+ reactions show extensive fragmentations and elimination steps generating hydrocarbon ions. The laser vaporization/polymerization method provides the ability to encapsulate several different metals or metal oxides which undoubtedly will play a significant role in tuning the various properties of the polymer composites.
Pulsed laser deposition process of PLZT thin films using an infrared Nd:YAG laser by T. García; E. de Posada; P. Bartolo-Pérez; J.L. Peña; R. Diamant; F. Calderón; A. Pelaíz (3783-3788).
Pulsed laser depositions of PLZT thin films were performed using an Nd:YAG (1064 nm) laser. The growths took place in vacuum or in an oxygen background. Room temperature and 500 °C were the used substrate temperatures. The X-ray diffraction analysis revealed a preferential crystallographic orientation in the films grown at room temperature in vacuum. Such result is discussed. The velocity distribution functions of the species in the plasma plume were obtained from a time of flight study using optical emission spectroscopy. The maximums of these distributions functions fall around 106 cm/s, equivalent to an energy range of 18–344 eV. Ionic species of heavy elements (like lead) achieved higher velocities than other lighter species. This result is linked to the creation of an accelerating spatial charge and to the thermal nature of the target material extraction that allows some elements to be released first than others. Chemical state variations of the elements present in the films were analyzed. Under these different growing conditions, lead chemical states varied the most.
Keywords: Laser ablation; PLD; Texture; PLZT; Thin films; XPS;
Chemical alteration of poly(vinyl fluoride) Tedlar® induced by exposure to vacuum ultraviolet radiation by Michael L. Everett; Gar B. Hoflund (3789-3798).
In this study the chemical alteration of poly(vinyl fluoride) Tedlar® by vacuum ultraviolet radiation (VUV) (115–400 nm) has been examined using X-ray photoelectron spectroscopy (XPS). The initial F/C atom ratio of 0.34 decreases to 0.17 after a 2-h exposure. The F/C atom ratio is further reduced to a steady-state value of approximately 0.04 after a 24-h exposure. Similarly, the O/C atom ratio is reduced from 0.08 to 0.05 and then to 0.02 during these two exposures. As the F and O are removed by VUV exposure, the C concentration increases from 70.5 to 82.0 and then to 94.6 at.% thus forming a graphitic or amorphous carbon-like layer which erodes more slowly than the virgin Tedlar surface. Exposure of the VUV-damaged surface to O2 results in chemisorption of O, indicating that reactive sites are formed during the chemical erosion by VUV. Further exposure to VUV removes this chemisorbed oxygen but a subsequent exposure to air at atmospheric conditions causes a three-fold increase in O chemisorbed at the surface. Comparison of XPS data indicates that the mechanisms of chemical alteration by VUV radiation and hyperthermal (∼5 eV) atomic oxygen (AO) are similar.
Keywords: Fluoromers; Fluoropolymers; Teflon; Tedlar; Tefzel; XPS; AO; VUV; Low earth orbit; LEO;
Asymmetric surface modification of poly(ethylene terephthalate) film by CF4 plasma immersion by Chun-Hsiang Wen; Miao-Ju Chuang; Ging-Ho Hsiue (3799-3805).
Poly(ethylene terephthalate) (PET) films were treated with CF4 plasma immersion. The samples were processed at different RF powers and treatment time. The surface modification of PET films was evaluated by water contact angle (CA), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). Decrease in contact angle of both sides of PET films was observed under mild treatment conditions. However, as raising treatment power and/or time, the change in contact angle between the two sides of PET films was different. The relatively hydrophobic and hydrophilic surfaces were being in situ formed on the two sides of PET films, respectively. And the extreme values of water contact angle reached 108.63 and 7.56°, respectively. XPS analyses revealed that there was a substantial incorporation of fluorine and/or oxygen atoms in both side surfaces. The relative chemical composition of the C (ls) spectra's showed the incorporation of non-polar fluorine-based functionalities (i.e. ―CF―CF n ―, ―CF2 ― or ―CF3 groups) and polar oxygen-based functionalities (i.e. ―COOH or ―OH groups) in the surfaces. Correlation between the plasma parameters and the surface modification of PET films is also discussed.
Keywords: Hydrophilic; Hydrophobic; PET; Plasma; XPS;
Ultraviolet photoelectron spectroscopy investigation of interface formation in an indium–tin oxide/fluorocarbon/organic semiconductor contact by S.W. Tong; K.M. Lau; H.Y. Sun; M.K. Fung; C.S. Lee; Y. Lifshitz; S.T. Lee (3806-3811).
It has been demonstrated that hole-injection in organic light-emitting devices (OLEDs) can be enhanced by inserting a UV-illuminated fluorocarbon (CF x ) layer between indium–tin oxide (ITO) and organic hole-transporting layer (HTL). In this work, the process of interface formation and electronic properties of the ITO/CF x /HTL interface were investigated with ultraviolet photoelectron spectroscopy. It was found that UV-illuminated fluorocarbon layer decreases the hole-injection barrier from ITO to α-napthylphenylbiphenyl diamine (NPB). Energy level diagrams deduced from the ultraviolet photoelectron spectroscopy (UPS) spectra show that the hole-injection barrier in ITO/UV-treated CF x /NPB is the smallest (0.46 eV), compared to that in the ITO/untreated CF x /NPB (0.60 eV) and the standard ITO/NPB interface (0.68 eV). The improved current density–voltage (I–V) characteristics in the UV-treated CF x -coated ITO contact are consistent with its smallest barrier height.
Effect of the dispersibility of ZrO2 nanoparticles in Ni–ZrO2 electroplated nanocomposite coatings on the mechanical properties of nanocomposite coatings by Fengyan Hou; Wei Wang; Hetong Guo (3812-3817).
ZrO2 nanoparticles was uniformly co-deposited into a nickel matrix by electroplating of nickel from a Watts bath containing particles in suspension which were monodispersed with dispersant under DC electrodeposition condition. It was found that morphology, orientation and hardness of the nanocomposite coatings with monodispersed ZrO2 nanoparticles had lots of difference from the nanocomposite coatings with agglomerated ZrO2 nanoparticles and pure nickel coatings. Especially, the result of hardness showed that only a very low volume percent (less than 1 wt.%) of monodispered ZrO2 nanoparticles in Ni–ZrO2 nanocomposite coatings would result in higher hardness of the coatings. The hardness of Ni–ZrO2 nanocomposite coatings with monodispersed and agglomerated ZrO2 nanoparticles were 529 and 393 HV, respectively. The hardness value of the former composite coatings was over 1.3 times higher than that of the later. All these composite coatings were two–three times higher than that of pure nickel plating (207 HV) prepared under the same condition. The strengthening mechanisms of the Ni–ZrO2 nanocomposite coatings based on a combination of grain refinement strengthening from nickel matrix grain refining and dispersion strengthening from dispersion state of ZrO2 nanoparticles in the coatings.
Keywords: Nanocomposites; Electroplating; Coatings; Hall-Patch; Orowan;
Self-assembled monolayers on magnesium alloy surfaces from carboxylate ions by Yali Liu; Zhanfeng Yu; Shuxue Zhou; Limin Wu (3818-3827).
Self-assembled monolayers (SAMs) of carboxylate salts (C n−1H2n−1COONa, n = 12, 16, 18) were successfully formed on Mg alloy substrate in ethanol solution and characterized by the contact angle measurement, ATR-FTIR, ellipsometry and XPS. The SAMs were regularly and densely anchored to the Mg alloy substrate via monodentate bonding with the tilting angles of about 40°, 33° and 27° for C12, C16 and C18 monolayers, respectively. Electrochemical impedance spectroscopy (EIS) proved the corrosion protection of SAMs for Mg alloy substrate with protective efficiency (PE) of even up to 98.5%.
Keywords: Self-assembled monolayer; Magnesium alloy; Alkylcarboxylate; Corrosion protection;
Electrical screening of ternary NiO–Mn2O3–Co3O4 composition spreads by D.A. Kukuruznyak; P. Ahmet; T. Chikyow; A. Yamamoto; F.S. Ohuchi (3828-3832).
The compositional optimization of infrared-transparent conducting oxides was performed using high throughput screening of combinatorial libraries. Complete ternary composition spreads of NiO–Mn2O3–Co3O4 alloys were deposited onto conducting Nb-doped SrTiO3 substrates using the pulsed laser deposition technique. Resistance–temperature relations of each composition in the spread were determined using a custom-designed scanning probe. The binary NiCo2O4 oxide showed the lowest electrical resistivity of about 0.1 Ω cm but unacceptably large resistance–temperature dependence (3.5%/°C). Electrically conducting ternary alloys along the line Mn0.45Ni0.63Co1.92O4–Mn0.60Ni0.72Co1.68O4–Mn0.69Ni0.81Co1.50O4 exhibited much lower temperature sensitivity (of about 1.5%/°C) as well as electrical resistance comparable to that of NiCo2O4. From this screening we propose new compounds for the thin-film ITCO sensors.
Keywords: Infrared-transparent oxide (ITCO); High-throughput combinatorial methods; Composition spreads; PLD; Scanning probe;
Wear-out of Al–Ta2O5/SiO2–Si structures under dynamic stress by N. Novkovski; E. Atanassova (3833-3836).
Wear-out of Al–Ta2O5/SiO2–Si stacked layers under dynamic current stresses was studied. It was found that a detrapping of negative charges occurs between the pulses, similarly to SiO2 and SiO x N y films. Additional consumption of the SiO2 interfacial layer results in a decrease of the gate voltage in some stages of the stress, depending upon the stress time and current density.
Keywords: ac stress; High-k dielectric; Charge trap; Metal gate;
Silane overpressure post-implant annealing of Al dopants in SiC: Cold wall CVD apparatus by S. Rao; F. Bergamini; R. Nipoti; S.E. Saddow (3837-3842).
We report on the successful post-implantation annealing of 4H-SiC samples that were implanted at elevated temperature with high-dose Al implants. Anneals at temperatures up to 1700 °C were conducted in a silane ambient at a process pressure of 150 Torr using a cold wall CVD reactor. A series of 30 min anneals were performed in 3% silane premixed in 97% UHP argon (Ar), which was further diluted in a 6 slm Ar carrier gas. The surface morphology of the samples was studied via plan-view secondary electron microscopy (SEM) and atomic force microscopy (AFM). The resulting surface morphology showed no evidence of step bunching or any other surface degradation. We also report the electrical characterization of Al+ implanted p+/n 4H-SiC diodes realized on samples that were annealed at 1600 °C. The current–voltage characteristics of the p+/n diodes and the resistivity of the implanted layer were measured at room temperature. Most of the diodes had a turn-on voltage of 1.75 V, with ideality factors of up to 1.2 and very low reverse leakage current at −100 V, corresponding to an average reverse leakage current density of (9.7 ± 0.4) × 10−9 A/cm2. The breakdown voltage was near the theoretical value for an epitaxial 4H-SiC layer. However, the resistivity value of the implanted Al+ layer was 11 Ω cm, which was an order magnitude higher than the expected value.
Keywords: Silicon carbide; Al implantation; Silane; Annealing; p+/n Junction diode;
Adsorption and desorption of Ca and PO4 species from SBFs on RF-sputtered calcium phosphate thin films by E. van der Wal; S.J. Oldenburg; T. Heij; A.W. Denier van der Gon; H.H. Brongersma; J.G.C. Wolke; J.A. Jansen; A.M. Vredenberg (3843-3854).
RF magnetron sputtering of calcium phosphate (CaP) coatings is a promising technique to apply thin bioactive films on bulk implant materials. In this paper the properties of the interface between RF sputtered coatings and simulated body fluids (SBFs) are related to the ability to form CaP crystals on the coating surface. Two types of coatings were compared: coatings with a low Ca over P ratio (∼0.8; CaPlow), which remain inert when immersed in SBF2 (i.e. SBF with twice the Ca and PO4 concentrations), and coatings with a high Ca over P ratio (1.6; CaPhigh), which show the formation of CaP crystals on their surface within 2 h. Low energy ion scattering (LEIS) and radioactive labeling of the SBFs combined with liquid scintillation counting (LSC) allowed us to study very accurately the composition of the adsorbates of both coating groups after 10 min of immersion in SBF2. For the adsorbate on CaPhigh and CaPlow coatings coverages were found consistent with ionic adsorption and Ca/P ratios of 1.24 ± 0.02 and 2.17 ± 0.10, respectively. Adsorption was found to be reversible over the studied immersion period. After an induction period of 40 min a CaP precipitate started to form on the CaPhigh coatings with a Ca/P ratio of 1.30 ± 0.02. Further, no significant desorption of coating species was observed during this induction period.
Keywords: Adsorption; Bioactivity; Calcium phosphate coating; Crystallisation; SBF (simulated body fluids); Surface analysis;
Theoretical analysis of optical properties of dielectric coatings dependence on substrate subsurface defects by Jian Shen; Shouhua Liu; Zicai Shen; Jianda Shao; Zhengxiu Fan (3855-3860).
A model for refractive index of stratified dielectric substrate was put forward according to theories of inhomogeneous coatings. The substrate was divided into surface layer, subsurface layer and bulk layer along the normal direction of its surface. Both the surface layer (separated into N 1 sublayers of uniform thickness) and subsurface layer (separated into N 2 sublayers of uniform thickness), whose refractive indices have different statistical distributions, are equivalent to inhomogeneous coatings, respectively. And theoretical deduction was carried out by employing characteristic matrix method of optical coatings. An example of mathematical calculation for optical properties of dielectric coatings had been presented. The computing results indicate that substrate subsurface defects can bring about additional bulk scattering and change propagation characteristic in thin film and substrate. Therefore, reflectance, reflective phase shift and phase difference of an assembly of coatings and substrate deviate from ideal conditions. The model will provide some beneficial theory directions for improving optical properties of dielectric coatings via substrate surface modification.
Keywords: Subsurface defects; Optical coatings; Dielectric coatings; Polarization;
Dry etching of ITO by magnetic pole enhanced inductively coupled plasma for display and biosensing devices by T. Meziani; P. Colpo; V. Lambertini; G. Ceccone; F. Rossi (3861-3870).
The dry etching of indium tin oxide (ITO) layers deposited on glass substrates was investigated in a high density inductively coupled plasma (ICP) source. This innovative low pressure plasma source uses a magnetic core in order to concentrate the electromagnetic energy on the plasma and thus provides for higher plasma density and better uniformity. Different gas mixtures were tested containing mainly hydrogen, argon and methane. In Ar/H2 mixtures and at constant bias voltage (−100 V), the etch rate shows a linear dependence with input power varying the same way as the ion density, which confirms the hypothesis that the etching process is mainly physical. In CH4/H2 mixtures, the etch rate goes through a maximum for 10% CH4 indicating a participation of the radicals to the etching process. However, the etch rate remains quite low with this type of gas mixture (around 10 nm/min) because the etching mechanism appears to be competing with a deposition process. With CH4/Ar mixtures, a similar feature appeared but the etch rate was much higher, reaching 130 nm/min at 10% of CH4 in Ar. The increase in etch rate with the addition of a small quantity of methane indicates that the physical etching process is enhanced by a chemical mechanism. The etching process was monitored by optical emission spectroscopy that appeared to be a valuable tool for endpoint detection.
Keywords: Ion etching; Plasma processing; Sputtering; Indium tin oxide; Atomic force microscopy; X-ray photoelectron spectroscopy;
Surface state of TiO2 treated with low ion energy plasma by Jin Jun; Joong-Hyeok Shin; Marshal Dhayal (3871-3877).
The effect of low pressure radio frequency (rf) plasma treatment on TiO2 surface states has been studied using X-ray photoelectron spectroscopy. Three different oxidation states of oxygen in untreated TiO2 powder were observed, which suggests the existence of adsorbed water and carbon on the surface. The ratio of oxygen to titanium (O/Ti) was decreased for the low ion dose plasma treated samples due to desorption of water from the surface. In the case of Ti 2p about 20% of surface states were converted to Ti3+ 2p3/2 state after plasma treatment with a very good stability, whereas untreated TiO2 remained mostly as Ti4+ state. A rapid decrease in the ratio of carbon to titanium (C/Ti) at TiO2 surface was also observed after plasma treatment and more than 90% of carbon atoms were removed from the surface. Therefore, the plasma treatment of TiO2 has advantages to surface carbon cleaning, increasing O− and Ti3+ surface states, hence improving the activity of TiO2 for different environmental, energy and biological applications.
Keywords: Plasma; Surface modification; TiO2; XPS;
Structural and tribological responses of phenolphthalein poly(ether sulfone) on electron irradiation by Xianqiang Pei; Qihua Wang; Jianmin Chen (3878-3883).
The blocks of phenolphthalein poly(ether sulfone) (PES-C) were prepared by hot pressing. Then the blocks were irradiated with electron beams under N2 atmosphere at room temperature. The structural and tribological responses of PES-C on electron irradiation were investigated. Results showed that partial degradation took place on the surface of PES-C after electron irradiation. Even so, the infrared spectra (FTIR) of PES-C after electron irradiation maintained much memory of the pristine sample, the reason for this might be due to the radiation-resistant property of PES-C and the less damage caused by the lower liner energy transfer of electron with respect to other ions. In addition, amorphous carbon and carbides formed on the surface of PES-C after electron irradiation. Friction and wear tests revealed that with increasing irradiation dose, it took more time for the friction coefficient to decrease from a higher value to a lower one and level off. And the wear rate decreased with the increase of irradiation dose. It was concluded that the variation of the tribological behavior of PES-C resulted from its structural responses on electron irradiation on the surface.
Keywords: Phenolphthalein poly(ether sulfone) (PES-C); Electron irradiation; Structure; Tribological properties;
Immobilization of pyrene via diethylenetriamine on quartz plate surface for recognition of dicarboxylic acids by Lining Gao; Yu Fang; Fengting Lü; Meiwen Cao; Liping Ding (3884-3893).
A novel photo-luminescence film has been prepared by immobilizing pyrene on a quartz plate surface via diethylenetriamine. Imino structure was intentionally introduced into the long flexible spacer due to their hydrogen bond forming abilities with carboxylic acids. It has been found that the film shows combined monomer and excimer emission of pyrene both in wet and dry states. Steady-state and time-resolved fluorescence emission measurements demonstrated that the excimer emission mainly came from direct excitation of ground state dimers, and/or monomers in aggregated state. The structures of the excimers formed during the excitation are mixtures of “standard excimers” and “distorted excimers” of the fluorophore moieties. Fluorescence lifetime measurements showed that the decay of the film is complex, and a four exponential fit is necessary for getting a satisfied result. The photophysical behavior of the present film could be rationalized by employing the model proposed before. Sensing property studies showed that the emission of the film is sensitive to the presence of dicarboxylic acids, including ethanedioic acid, malonic acid, etc. In contrast, presence of monocarboxylic acids, such as formic acid and acetic acid, had little effect upon the fluorescence emission of the film. Compared with the films taking ethylenediamine or 1,3-diaminopropane as their spacer component, introduction of diethylenetriamine into the spacer improved the performance of the film greatly. In addition, the sensing process is reversible, and the film is stable within a number of months provided it is properly preserved. These characteristics showed that the film is worthwhile for further exploration.
Keywords: Pyrene; Fluorescence; Sensing; Dicarboxylic acids;
Cr–Ni–Mo–Co surface alloying layer formed by plasma surface alloying in pure iron by Xiaoping Liu; Yuan Gao; Zhonghou Li; Zhong Xu; Wenhuai Tian; Bin Tang (3894-3902).
Using double glow plasma alloying technique, a multi-elements alloyed layer containing elements of Cr, Ni, Mo and Co was formed on the surface of pure iron. After undergoing suitable aging treatment followed solid solution treatment, the formed alloying layer keeps a good combination of corrosion resistance and wear resistance. The relationship between the process parameters of heat treatments and the properties of the formed Cr–Ni–Mo–Co alloying layer, such as the chemical composition, hardness, corrosion resistance and wear resistance, was investigated in this study. It was revealed that the formed alloying layer exhibits a better behavior than that of 304 stainless steel and pure iron by employing a suitable heat treatment system. The temperature employed in solid solution treatment is 1453 K (1180 °C) followed by water quenching and the aging temperature is 813 K (540 °C) followed by water cooling.
Keywords: Plasma surface alloying; Solution treatment; Aging; Corrosion resistance; Wear resistance;
Electronic properties of nanoporous TiO2 films investigated in real space by means of scanning tunnelling spectroscopy by Volker Jacobsen; Michael Dürr; Bettina Wendling; Akio Yasuda; Gabriele Nelles; Wolfgang Knoll; Maximilian Kreiter (3903-3911).
Nanoporous TiO2 films with a thickness between 100 nm and 8 μm were studied by scanning tunnelling spectroscopy. The bias voltage of significantly increased differential conductivity, indicating the conduction and valence bands, was found to be strongly dependent on layer thickness and the underlying substrate material. This effect is traced back to the high resistivity of the oxide films and the formation of Schottky barriers at the TiO2–substrate contact. All films showed a strong hysteresis as a function of sweep direction of the bias voltage pointing towards the existence of a high number of localized electronic trap states. This effect is getting even more pronounced upon sample ageing. Laterally resolved measurements show that the major part of the surface exhibits similar I(V) characteristics with minor deviations, while smaller areas with significantly different response are identified. These areas are comparable in size to the individual crystals the material is composed of.
Keywords: Titanium dioxide; Nanocrystalline film; Scanning tunneling spectroscopy; Intraband states; Solar cell;
Plasma-polymerized thiophene films for enhanced rubber–steel bonding by James L. Delattre; Riccardo d’Agostino; Francesco Fracassi (3912-3919).
Thin films of plasma-polymerized thiophene (PPTh) were deposited on cold-rolled steel substrates to improve adhesion to rubber compounds. PPTh films were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and atomic force microscopy. The ratio of carbon-to-sulfur found in PPTh films is 4:1, suggesting the monomer structure is generally intact, which was supported by FT-IR absorptions characteristic of polymerized thiophene rings. However, some fragmentation did occur to give acetylenic and aliphatic groups. Steel–rubber adhesion measurements, performed in accordance with the ASTM 429-B peel test, strongly depended on cleaning and pretreatment methods as well as film thickness. Best results were obtained on polished steel samples that were cleaned with acid, pretreated with a hydrogen/argon plasma, then coated with 50 Å of PPTh film. These samples exhibited a peel force of 14.3 N/mm, which is comparable to that of polished brass control samples. Depth-profiling XPS analysis of the rubber–steel interface showed the existence of an iron sulfide layer which is likely responsible for the strong adhesion.
Keywords: Thiophene; Plasma-assisted CVD; Adhesion-solid surfaces and interfaces; Depth-profiling; Rubber; Steel;