Showing papers in "Applied Surface Science in 2001"
TL;DR: In this article, X-ray photoelectron spectroscopic (XPS) study on carbon-supported Pt, Pt-Co and Pt-Cr electrocatalyst suggests the presence of a relatively lower Pt-oxide content on the alloys.
Abstract: Cathodic reduction of oxygen in fuel cells is known to be enhanced on platinum alloys in relation to the platinum metal The higher performance of the platinum alloys is as a result of the improved oxygen-reduction kinetics on the alloys but there is hardly any increase in the electrode platinum-surface-areas for the platinum alloys as compared to the platinum metal, and thus the higher performance is solely due to the enhanced electrocatalytic activity of the alloys as compared to the platinum metal The present X-ray photoelectron spectroscopic (XPS) study on carbon-supported Pt, Pt–Co and Pt–Co–Cr electrocatalysts suggests the presence of a relatively lower Pt-oxide content on the alloys The X-ray powder diffraction patterns for these electrocatalysts show that while the carbon-supported platinum electrocatalyst has a face-centered cubic (fcc) phase, carbon-supported Pt–Co and Pt–Co–Cr electrocatalysts exhibit a face-centered tetragonal (fct) phase But, Pt electrocatalyst has a lower particle-size and, hence, a higher dispersion Previous studies have shown higher activities on the Pt-alloys than on Pt, and have attributed it to changes in the electronic and structural characteristics of Pt These changes can be correlated with the lower oxidation-state of Pt sites, as found in this study
322 citations
TL;DR: In this article, the surface properties of ZnO ultrafine particles were studied using TEM, XRD, BET, SPS, EPR, IR, and XPS.
Abstract: We prepared ZnO ultrafine particles (UFPs) by thermal decomposition of the precursor zinc carbonate hydroxide. The surface properties of the as-prepared particles were studied using TEM, XRD, BET, SPS, EPR, IR, and XPS. The surface contains active species such as oxygen deficiencies and hydroxyl that improve photocatalytic activities. The concentrations of active species decreased as the calcination temperature increased along with the surface areas and photovoltage. The ZnO UFP have a significant EPR signal resulting from O2− deficiencies on the surface, which can capture and trap electrons. During photocatalytic degradation of phenol, the photocatalytic activities of the particles decreased as their size increased, which means that these activities depend mainly on surface properties.
319 citations
TL;DR: In this article, an attention was paid on the sputtering pressure of Ar during the film deposition, and it has been found that electrical conductivity, gas sensitivity and rising response time of the thin film depends on Sputtering pressure during the deposition process.
Abstract: Gallium oxide thin film has properties of n-type semiconductor and it is stable at high temperature. The resistivity of Ga2O3 changes with the concentration of oxygen in the thin film. An oxygen sensor was made on the basis of this principle. Gallium oxide thin film was deposited on the Si substrate from a sintered powder target by a rf magnetron sputtering using Ar as the sputtering gas. The sputtering condition is a very important factor to control the oxygen content of the Ga2O3 thin film and hence the response characteristics of the sensor. In this present paper, an attention was paid on the sputtering pressure of Ar during the film deposition. It has been found that electrical conductivity, gas sensitivity and rising response time of the thin film depends on sputtering pressure of Ar during the deposition process. It has also been clarified that gallium oxide thin film deposited in lower sputtering pressure shows better electrical conductivity and rising response time, whereas the thin film deposited in high sputtering pressure shows higher gas sensitivity. The difference in characteristics of the deposited thin films may be considered due to the surface structure as revealed from the AFM observation.
255 citations
TL;DR: The surface oxidation of polycrystalline silver foil by reaction with ozone (5 mol% O3 in O2) at 300 K and ambient pressure was investigated in this paper, where the morphology, microstructure and chemical composition of the oxide scale which developed on the foil surface during exposure to ozone was characterised by scanning electron microscopy.
Abstract: The surface oxidation of a polycrystalline silver foil by reaction with ozone (5 mol% O3 in O2) at 300 K and ambient pressure was investigated. The morphology, microstructure and chemical composition of the oxide scale which developed on the foil surface during exposure to ozone was characterised by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The surface of silver foil was rapidly oxidised upon contact with ozone, initially producing a thick Ag2O protective film. After 10 min reaction, the oxide film thickness was around 8–10 μm. SEM analysis revealed that Ag2O film thickening occurred via a discontinuous film growth mechanism. Growth stresses, resulting from the large lattice volume mismatch between the oxide and the metal, caused the oxide film to crack and flake extensively during development. Spallation of the oxide film exposed fresh silver metal to ozone, which lead to further Ag2O deposition. The continued recurrence of this process resulted in the formation a thick, discontinuous Ag2O film on the silver foil. After foil exposure to ozone for 300 min, the oxide film thickness was 17–20 μm. Furthermore, Ag2O at the surface of the oxide film was slowly oxidised to AgO with prolonged exposure to ozone. The combined results of our experimental studies were used to develop a better understanding of the oxidation of silver surfaces by O3.
238 citations
TL;DR: In this article, Lanthanum oxide thin film deposition by atomic layer epitaxy (ALE) was studied at 180-425°C on soda-lime glass and Si(1-0-0) substrates using a β-diketonate type precursor La(thd) 3 and ozone.
Abstract: Lanthanum oxide thin film deposition by atomic layer epitaxy (ALE) was studied at 180–425°C on soda-lime glass and Si(1 0 0) substrates using a β-diketonate type precursor La(thd) 3 and ozone. The chemical constituents of the films were analyzed by TOF-ERDA, RBS and FTIR while XRD and AFM were used to determine the crystallinity and surface morphology. Films grown below 275°C were amorphous La 2 O 2 CO 3 , while at deposition temperatures above 300°C XRD patterns indicated that cubic La 2 O 3 phase was formed. All the films were transparent and uniform with only small thickness variations. Carbonate type impurity was found in all films, but the carbon content of the films decreased with growth temperature being 3 at.% in films grown above 400°C. Hexagonal La 2 O 3 was obtained when the films grown on silicon substrates were annealed at 800°C or above in a nitrogen flow. The as-deposited cubic and annealed hexagonal La 2 O 3 films were found to be chemically unstable in ambient air since a transformation to monoclinic LaO(OH) and hexagonal La(OH) 3 was detected, respectively.
237 citations
TL;DR: In this paper, the surface oxide films on a Co-Cr-Mo alloy located in various environments were characterized to estimate the reconstruction of the film in the human body and the results from angle-resolved XPS revealed that chromium and molybdenum were more widely distributed in the inner layer than in the outer layer of the oxide film.
Abstract: The purpose of this study was to characterize the surface oxide films on a Co–Cr–Mo alloy located in various environments to estimate the reconstruction of the film in the human body. Five kinds of specimens were prepared according to the following methods: polishing in deionized water, autoclaving, immersion in Hanks’ solution, immersion in a cell culture medium, and incubation with cultured cells. X-ray photoelectron spectroscopy (XPS) was performed to estimate the compositions of the surface oxide film and substrate and the thickness of the film. The surface oxide was about 2.5 nm thick and contained a large amount of OH − . Calcium phosphate was formed after immersion in the Hanks’ solution and the culture medium and incubation with the cultured cells. Cobalt was dissolved during immersion in Hanks’ solution and the cell culture medium and incubation in a cell culture. After the dissolution, the surface oxide consisted of chromium oxide (Cr 3+ ) containing molybdenum oxide (Mo 4+ , Mo 5+ , and Mo 6+ ). Results from angle-resolved XPS revealed that chromium and molybdenum were more widely distributed in the inner layer than in the outer layer of the oxide film. The results in this study suggest that Co–Cr–Mo alloy releases cobalt and that the surface oxide film consisting of chromium and molybdenum is reconstructed in living tissues.
235 citations
TL;DR: In this paper, a real-time quartz crystal microbalance method was used to determine the growth rate of TiCl 4/H 2 O ALD at substrate temperatures of 100-400°C.
Abstract: Atomic layer deposition (ALD) of titanium dioxide from TiCl 4 and H 2 O was studied at substrate temperatures of 100–400°C. Using a real-time quartz crystal microbalance method, it was demonstrated that although the surface reactions were self-limited, the growth rate depended on the temperature and development of the thin film structure. Relatively low growth rate which was obtained in the TiCl 4 /H 2 O ALD process, was found to be a result of a significant chlorine amount adsorbed during the TiCl 4 pulse. Surface intermediates formed in the initial stage of TiCl 4 adsorption were unstable and weakly bonded to the surface. Desorption and decomposition of these species additionally influenced the deposition rate and, especially, its dependence on the precursor pulse times.
203 citations
TL;DR: In this article, the effect of Zn on hydrogenation of formate to dioxomethylene on the Cu(1.1) surface was studied using a density functional theory-generalized gradient approximation (DFT-GGA)-pseudopotential method.
Abstract: We have studied the effect of Zn on hydrogenation of formate to dioxomethylene on the Cu(1 1 1) surface by using a density functional theory–generalized gradient approximation (DFT–GGA)-pseudopotential method. We show that substitutionally adsorbed Zn changes the stability of intermediate states and the activation barrier of the hydrogenation process only slightly. On the other hand, the Zn atom adsorbed on the Cu surface stabilizes all formate, transition state, and dioxomethylene relative to the gas-phase molecules. Our results support a previously proposed reaction scheme that the adsorption state of Zn changes from substitutional to on-surface adsorption during the methanol synthesis.
196 citations
TL;DR: In this article, the authors used the chemical vapor deposition of 2,4-pentanedionate copper(II) as a precursor and fiberglass as substrate for the purpose of utilizing copper oxides over fiberglass.
Abstract: With the purpose of utilizing copper oxides over fiberglass as a novel catalyst material in oxidation reactions, we have used the chemical vapor deposition of 2,4-pentanedionate copper(II) as a precursor and fiberglass as substrate. The deposition of copper oxides was achieved in a horizontal-flow reactor using O2 as carrier-reactant gas at several deposition temperatures. Copper species deposited on fiberglass were characterized by X-ray diffraction (XRD), UV–visible spectrophotometry (UV–VIs) and scanning electronic microscopy (SEM) techniques. The fiberglass coated with copper oxides showed a catalytic activity for the oxidation of ethanol into a stream of air at different temperatures in a pulse microreactor.
192 citations
TL;DR: In this article, mixed layers of Al and Ce oxides have been obtained in conversion coatings on two aluminum alloys (AA6061 and AA2618) and the microstructure and the chemical composition of the protective films have been examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS).
Abstract: Mixed layers of Al and Ce oxides have been obtained in conversion coatings on two aluminum alloys (AA6061 and AA2618). The microstructure and the chemical composition of the protective films have been examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The corrosion resistance in NaCl solution was investigated and a comparison with a traditional chromate conversion coating on the same alloys is given. The coatings obtained by immersion in boiling solution of Ce(III) salts cover uniformly the alloys surface with a protective layer, whereas the H 2 O 2 –cerium conversion coating process produces a thick, but cracked layer with “dry-mud” morphology, which preferentially covers the intermetallic particles on the samples surface. The boiled cerium conversion coating treatments are as effective in corrosion resistance as the traditional chromating process, but the interest for industrial purposes is limited because of long application times. The H 2 O 2 –cerium conversion coating process produces effective corrosion resistance layers, thinner than the ones obtained by traditional processing, but very interesting for industrial applications due to the limited environmental impact.
188 citations
TL;DR: In this paper, the surface properties of two carbon fibers were investigated using X-ray photoelectron spectroscopy (XPS) to determine the role of surface treatment in improving the properties of a carbon fiber composite.
Abstract: X-ray photoelectron spectroscopy (XPS) has been used to investigate the surface characteristics of two carbon fibers and determine the role of surface treatment in improving the properties of a carbon fiber composite. Carbon and oxygen were the major elements observed on the surface of the carbon fiber samples. Small amounts of lightly oxidized nitrogen amounting to about 3 at.% were detected on the surface of thermally oxidized carbon fiber in a gas mixture of O 2 /(N 2 +O 2 ). Graphitic carbon was the major carbon functional component on the surface of carbon fiber samples but other functional forms of carbon were also present such as C–O, CO, and O–CO. The biggest differences in the surface chemistry between the carbon fibers with and without surface treatment was in the carbonyl group (CO) content. Thermal oxidation processing in a gas mixture of O 2 /(N 2 +O 2 ) can be employed to increase the carbonyl functional group which is the main contributor in improving the interlaminar shear strengths of carbon fiber composite materials.
TL;DR: In this article, c-axis oriented lithium-doped zinc oxide (ZnO:Li) thin films were prepared on Pyrex borosilicate glass substrates by a sol-gel method starting from zinc acetate dihydrate, lithium chloride, 2-methoxyethanol and monoethanolamine.
Abstract: Preferentially, c -axis-oriented lithium-doped zinc oxide (ZnO:Li) thin films were prepared on Pyrex borosilicate glass substrates by a sol–gel method starting from zinc acetate dihydrate, lithium chloride, 2-methoxyethanol and monoethanolamine. Decomposition and crystallization behavior of dip-coated amorphous precursor films during post-annealing treatments were investigated by thermogravimetry–differential thermal analysis (TG–DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), optical transmittance measurements, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). It was revealed that the films contained the organic compounds at temperatures up to 300°C, which was the key to the transformation from the amorphous to the crystalline state. Thermodynamical consideration of nucleation and crystal growth was made taking account of surface energies of the film and the glass substrate and an interfacial energy between them. Mechanisms underlying the c -axis orientation were proposed based upon the initial orientation due to nucleation and final growth orientation.
TL;DR: In this paper, the binding energies associated with the 2p 3/2, 3d, and Auger lines in the X-ray photoemission spectra were measured and an assignment of the photoelectron peaks to various chemical states was proposed.
Abstract: In this paper, by the use of X-ray photoelectron spectroscopy, we unequivocally identify the oxides present on GaAs surfaces and accurately measure the binding energies associated with the 2p 3/2 , 3d, and Auger lines in the X-ray photoemission spectra. These measurements intended to provide reliable reference data for further work. We conducted an extensive analysis of the oxidation states of Ga metal and oxide powder reference samples, air exposed GaAs wafers, and wafers subjected to various surface treatments (argon plasma treatments and boiling). Based on this experimental evidence, an assignment of the photoelectron peaks to various chemical states is proposed.
TL;DR: In this article, self-assembled 3-mercaptopropyltrimethoxysilane (MPTMS) layers on hydroxyl-terminated silicon oxide (SiO2) were prepared at MPTMS concentrations ranging from 5×10−3 to 4×10 −2 M.
Abstract: Self-assembled 3-mercaptopropyltrimethoxysilane (MPTMS, (CH3O)3SiCH2CH2CH2SH) layers on hydroxyl-terminated silicon oxide (SiO2) were prepared at MPTMS concentrations ranging from 5×10−3 to 4×10 −2 M . The surface structure and morphology of MPTMS layers were characterized by X-ray photoelectron spectroscopy (XPS), contact angle measurements, scanning electron microscopy (SEM), and atomic force microscopy (AFM). We found that the MPTMS layers on SiO2 consisted of dispersed domains 20–200 nm in diameter, instead of continuous, flat monolayers. With increasing MPTMS concentration, the domain shape changed from flat to steep. Flat domains were composed of well-ordered monolayers with thiol headgroups uniformly distributed on the uppermost surface, whereas steep domains were composed of disordered polymers with randomly distributed thiol headgroups on the uppermost surface. These results indicate that MPTMS molecules show good self-assembly at an MPTMS concentration of 5×10 −3 M , but not above this concentration. The effect of MPTMS concentration on the structure and morphology of MPTMS layers might be due to the competition between self-polymerization and surface dehydration reactions, which depends on the trace quantity of water in the solvent and on the SiO2 surface. Our research further indicates that MPTMS and water concentrations are the controlling parameters for preparing well-ordered, self-assembled MPTMS monolayers on SiO2.
TL;DR: In this article, the surface modification of silicas using silane coupling agents is described and the best modifiers were selected, which inducted a change of the silica surface from hydrophilic to hydrophobic.
Abstract: Silicas of highly dispersion degree were obtained. This process includes formation of silica particles and their aggregation. The ethylene glycol solution was used in precipitation process, resulting in a partial blocking of the silica surface hydroxyl groups (silanol groups) and, thus, in a decreased hydrophilicity of silica. Studies on the surface modification of silicas using silane coupling agents are described. The best modifiers were selected, which inducted a change of the silica surface from hydrophilic to hydrophobic. Basic physicochemical analyses of the obtained silicas were performed. The methods of evaluating the degree of surface modification of the silica were presented. Near infrared spectroscopy (NIR) was used to determine the degree of condensation of the silica surface silanol groups. The degree of hydrophobization of silica surface was determined by a calorimetric method. Moreover, studies on morphology and microstructure using transmission electron microscopy (TEM) were performed. Size distribution of primary particles and aggregates and agglomerates structures were determined by ZetaPlus instrument using dynamic light scattering (DLS) method.
TL;DR: In this article, the sulphur surface sites of pristine marcasite surfaces and their reactivity during initial air oxidation were investigated for the first time using synchrotron radiation excited photoelectron spectroscopy (SRXPS).
Abstract: The sulphur surface sites of pristine marcasite surfaces and their reactivity during initial air oxidation were investigated for the first time using synchrotron radiation excited photoelectron spectroscopy (SRXPS). Both S 2p and Fe 2p spectra were collected and compared to those of the polymorph pyrite. A new sulphur surface component is found additionally to the two known pyrite surface signals. Due to the non-isotropic character of the orthorhombic marcasite structure, its peak intensity depends strongly on the surface orientation. Its binding energy is close to the region of short-chained polysulphides. The signal is assigned to sulphur trimers produced by electron transfer between surface near sulphur dimers and S− formed after ruptures of SS bonds which results in S2− and S32−. In the cubic crystal arrangement of pyrite the stabilisation of S− to S2− is realised by an electron transfer from iron to sulphur only. A confirmation of this assumption is found in the Fe 2p spectra. The contribution of Fe3+ species — a result of the electron transfer process — is considerably less pronounced for marcasite. The mechanism of initial oxidation is different for marcasite and pyrite. The sulphur species responsible for the new spectroscopic component are the most reactive sites at the marcasite surface, while S2− is oxidised first in case of pyrite. The signals indicating the products of marcasite oxidation in the S 2p spectrum are less intense as expected from the intensity decreasing of the trimer peak. Therefore, an oxidation of sulphur trimers to elemental sulphur is assumed which could not be detected because of its volatility in the vacuum of the air lock system.
TL;DR: The reducibility and characteristics of CO microreactor gas chromatography, specific surface area, pore volume, H 2 -temperature-programmed reduction (TPR), and X-ray diffraction Rietveld analysis were examined by means of a CO micro reactor.
Abstract: The reducibility and characteristics of CuO, CeO 2 and CuO/CeO 2 catalysts were examined by means of a CO microreactor gas chromatography, specific surface area, pore volume, H 2 -temperature-programmed reduction (TPR), and X-ray diffraction Rietveld analysis. Experimental results showed that the specific surface area and pore volume of the CuO/CeO 2 catalysts decreased with an increase in CuO loading, whereas the average pore diameter was the same. TPR data exhibited two peaks, a low-temperature one due to the reduction of highly dispersed copper oxide and a high-temperature one due to the reduction of bulk CuO. Micro-structural analysis showed that the lattice constant of pure CeO 2 is 0.54103 nm. In contrast, when CuO/CeO 2 was formed, the cell parameter values of CeO 2 for various loading were all smaller than that of pure CeO 2 , indicating that some CuO entered the CeO 2 lattice. At a CuO loading of 5.0 wt.%, the crystalline size of CuO became minimal and the micro-strain maximal, indicating crystalline CuO and a high surface energy with a resulting best activity for CO oxidation. CuO/CeO 2 catalysts are stable to 750°C, but at 900°C the crystallite size increased rapidly and the CuO and CeO 2 phase-separated.
TL;DR: In this paper, the authors present results on the ablation rates of metals (such as Al, Cu, Ni, Ti, Mo, Pt, Zn, Cr and Si), the SRM NIST 600 series glasses and natural calcium fluoride for laser fluencies between 3.5 and 35 J/cm2 using argon or helium as ablation environment together with two fundamentally different types of lasers (193 nm Excimer and 266 nm Nd:YAG).
Abstract: Laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS) is a versatile micro-analytical technique for the determination of major, minor and trace elements in solid materials. Recent interest has concentrated on using the technique for layer analysis or depth profiling. However, little data has been published on the rates of ablation which provide essential information for determining depth resolution. Knowledge of the ablation rates is essential for the selection of optimum laser parameters for different target materials. It also provides estimates of uncertainties for quantification on materials where no internal standard is available to correct for differences in ablation volume. This work presents results on the ablation rates of metals (such as Al, Cu, Ni, Ti, Mo, Pt, Zn, Cr and Si), the SRM NIST 600 series glasses and natural calcium fluoride for laser fluencies between 3.5 and 35 J/cm2 using argon or helium as ablation environment together with two fundamentally different types of lasers (193 nm Excimer and 266 nm Nd:YAG).
TL;DR: In this paper, the authors investigated the electroless Cu coating of fly-ash cenosphere particles in detail using focused ion beam spectroscopy (FIB) and X-ray diffraction.
Abstract: Electroless Cu coating process involving Sn–Pd catalyst system is successfully utilized to coat Cu on the surface of fly-ash cenosphere particles to impart electrical conductivity to these non-conducting oxide ceramic particles. The low density Cu-coated cenosphere particles may be utilized for manufacturing conducting polymers for EMI shielding applications. This is the first report in the open literature to investigate the electroless Cu coating of fly-ash cenosphere particles in detail. Extensive characterization of coated particles is carried out by scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), focused ion beam spectroscopy (FIB), and X-ray diffraction (XRD) techniques to study the coating process and to show successful deposition of pure Cu. The mechanism of electroless Cu coating is mainly studied with the help of XPS, which shows the reduction of PdCl 2 (activator) catalyst on the surface of cenosphere particles by SnCl 2 (sensitizer) to produce pure Pd 0 clusters, which subsequently act as nucleation sites for Cu deposition. The concept of XPS core-level binding energy (BE) shift due to small cluster size is utilized to predict the size of pure Pd 0 clusters deposited on the fly-ash particle surface after the activation step. For the first time, the use of FIB technique is described and demonstrated to determine directly the Cu coating thickness.
TL;DR: In this article, the effects of rare earth oxide CeO2 and La2O3 on the microstructure and wear resistance of laser-clad nickel-based alloy coatings were investigated.
Abstract: The effects of rare earth oxide CeO2 and La2O3 on the microstructure and wear resistance of laser-clad nickel-based alloy coatings were investigated. The nickel-based alloy powders with different contents of CeO2 or La2O3 were laser-clad on to a steel substrate. The coatings were examined and tested for microstructural features, compositions, phase structure, and wear resistance. The results were compared with those for coatings without CeO2 and La2O3. The comparison indicated that the additions of rare earth oxide CeO2 or La2O3 can refine and purify the microstructure of coatings, reduce the dilution of clad material from base metal, form some new hard crystallographic phase and increase the microhardness of the coatings. As a result, by CeO2 or La2O3 addition, the friction coefficient of the coatings was decreased and the wear resistance of the coatings was enhanced significantly. The mechanism of these effects is also discussed in this paper.
TL;DR: In this paper, the micro-Raman scattering spectra of the films were compared to the results obtained by annealing the as-deposited VO 2 (B) film and the surface of the annealed film consisted of three regions of the black V 6 O 13 region, the yellow VO 2(B) region and the white non-crystalline region.
Abstract: Highly oriented VO 2 (B), V 6 O 13 , and V 2 O 5 thin films have been deposited on fused silica substrates by RF magnetron sputtering. X-ray diffraction characterization revealed that all the three films were single phases and strongly oriented with the (0 0 1) planes parallel to the substrates. The micro-Raman scattering spectra of the films were reported. The results were compared to the micro-Raman scattering spectra of the film obtained by annealing the as-deposited VO 2 (B) film. It was found that the surface of the annealed film consisted of three regions of the black V 6 O 13 region, the yellow VO 2 (B) region and the white non-crystalline region.
TL;DR: In this paper, ZnS/Ag/ZnS nano-multilayers for transparent electrodes in flat display application have been prepared by thermal evaporation in vacuum.
Abstract: In this paper, ZnS/Ag/ZnS nano-multilayers for transparent electrodes in flat display application have been prepared by thermal evaporation in vacuum. The sheet resistance of the films was low as 3 Ω/cm2. And they can be applied as good selective filters with the luminous transmittance Tlum about 90% and IR reflectance above 90%. The merit FTC for revaluing transparent electrodes reached 7.3×10 −2 Ω −1 at 550 nm wavelength. Among the prepared films, some extreme asymmetrical structures having good performances were firstly reported. The influence of thickness of layers on the optic and electrical performance and thermal stability of multilayers was analyzed. Spectroscopic ellipsometry analysis indicated that the interlayers between Ag and ZnS layer contained a physical mixture layer and a compound semiconductor layer. After heat treatment, there existed a vulcanized Ag layer and the further diffusion and chemical combination between layers, which reduced the transmittance and the conductivity of the whole system.
TL;DR: In this article, a model for dopant distribution in the fine powders was proposed, where the doping element is built into the lattice of SnO 2 partially and the residue substitutes Sn atoms in the topmost layer.
Abstract: Various doped tin oxide (dopants Sb, Nb, In) were prepared. By means of X-ray photoelectron spectroscopy (XPS) the dependence of the surface concentration on doping element, doping concentration and preparation technique was determined. Simultaneously, the electrical and morphological properties are strongly influenced even by low doping concentration. The dopant distribution was studied by XPS and SIMS depth profiling. A model for dopant distribution in the fine powders was proposed. At low concentrations, the doping element is build into the lattice of SnO 2 partially and the residue substitutes Sn atoms in the topmost layer. Particles of the second phase are found at higher doping concentrations. Additionally, the analysis of Sb 3d 3/2 peak position and shape in Sb doped samples shows a decrease of oxidation state of antimony with increasing doping concentration.
TL;DR: In this article, a cubic phase of HfO2 was observed by reflection high-energy electron diffraction in nanocrystalline thin films grown by atomic layer deposition from HfCl4 and H2O at substrate temperatures of 880-940°C.
Abstract: High-temperature cubic phase of HfO2 was observed by reflection high-energy electron diffraction in nanocrystalline thin films grown by atomic layer deposition from HfCl4 and H2O at substrate temperatures of 880–940°C. The phase was formed at properly chosen precursor doses and it was observed on the surface of films, which according to X-ray diffraction data consisted of monoclinic HfO2. The thickness of the surface layer, in which the cubic phase appeared, was estimated to be 5–10 nm. According to Auger electron spectroscopy data, formation of the cubic phase was accompanied with an increase in the ionicity of O–Hf bonds.
TL;DR: The thickness dependence of structural, optical and electrical properties of ZnO:Al films on polypropylene adipate (PPA) substrates have been studied in this paper, where it was observed that with an increase in film thickness, the crystallite sizes and the density of the films were increased, the resistivity was decreased, and the average transmittance in the wavelength range of the visible spectrum was also slightly decreased.
Abstract: The thickness dependence of structural, optical and electrical properties of the ZnO:Al films on polypropylene adipate (PPA) substrates have been studied. It was observed that with an increase in film thickness, the crystallite sizes and the density of the films were increased, the resistivity was decreased, and the average transmittance in the wavelength range of the visible spectrum was also slightly decreased.
TL;DR: In this paper, the surface chemical state of two carbon nanotube materials and the evidence of surface modification from a reaction with dichlorocarbene were determined using X-ray photoelectron spectroscopy (XPS).
Abstract: X-ray photoelectron spectroscopy (XPS) has been used to investigate the surface chemical state of two carbon nanotube materials and determine the evidence of surface modification from a reaction with dichlorocarbene. Carbon and oxygen were the major elements observed on the surface of the pristine carbon nanotube produced by electric arc discharge. After reaction with dichlorocarbene, chlorine atoms amounting to about 1.6 at.% were detected and the peak position of Cl 2p was at 201.3 eV, which can be attributed to existence of organic chlorocarbons. A new intense peak addition to the peak at 285 eV for the elemental sp 2 and sp 3 carbon atoms appears at the binding energy of about 287.5 eV in the C 1s narrow scan spectrum. This binding energy is typical for C 1s ionization of sp 3 carbon in organic chlorocarbons. It was found that CC was the major carbon functional component in the surface modified carbon nanotube but other functional forms of carbon were also present such as CCl, CO, and OCO. With Ar + ion sputtering, the atomic percent concentration of chlorine decreased by 65%, the carbon concentration increased significantly and the oxygen surface concentration decreased from 20.7 to 5.5 at.%. The surface chemical treatment with dichlorocarbene has thus modified the surface of the carbon nanotube with localization of small amounts of chlorine atoms on the carbon surface without disrupting the single walled nanotube bundles.
TL;DR: In this article, the behavior of polypyrrole and carboximethylcellulose (Ppy/CMC) prepared by different methods in order to prevent the corrosion of steel was described.
Abstract: This report describes the behaviour of polypyrrole and polypyrrole/carboximethylcellulose (Ppy/CMC) prepared by different methods in order to prevent the corrosion of steel. Potentiodynamic polarization curves and open circuit potential were used to evaluate the capacity of these materials to protect the surface. The results obtained allowed to assume that Ppy/CMC is better material to prevent corrosion than polypyrrole (Ppy) and potentiostatic method better than galvanostatic to obtain the deposit.
TL;DR: In this paper, the influence of tip size on surface roughness measurements by atomic force microscopy (AFM) was evaluated experimentally, and two different trends were observed for measured surface roughs as a function of tip sizes.
Abstract: The influence of tip size on surface roughness measurements by atomic force microscopy (AFM) was evaluated experimentally. Images of quartz over a lateral scan range of 125–5000 nm were measured by AFM utilizing tips of different sizes. Tip size was quantified by transmission electron microscopy before and after AFM imaging. Only tips whose size remained relatively constant during imaging were used in this study. Two different trends were observed for measured surface roughness as a function of tip size. At small lateral scan sizes (≤500 nm), the image root mean square roughness decreased as tip size increased. However, at larger scan sizes (e.g. 5000 nm), the roughness increased with increasing tip size. A simple two-dimensional model was developed to explain both trends.
TL;DR: In this paper, a self-assembly method was used to protect magnetic nanoparticles via surfactant-mediated selfassembly and their stable suspension in a variety of appropriate liquid media.
Abstract: Protectively and functionally coated magnetic nanoparticles are of special interest because of their important technological applications in diverse fields, ranging from biotechnology to transportation. In this paper, monolayer and bilayer surfactant coating on magnetite (Fe3O4) nanoparticles has been obtained using the self-assembly method. Magnetic properties such as magnetization, ZFC and FC curves, blocking temperature, hysteresis loop, coercivity and remanent magnetization of the SAM and bilayer coated magnetite nanoparticles have been investigated. The results show the efficacy of our synthesis approach not only to protect magnetic nanoparticles via surfactant-mediated self-assembly but also their stable suspension in a variety of appropriate liquid media. The superparamagnetic nature of the magnetic nanoparticles remains unchanged with self-assembled coatings and paves the way for their use in colloid suspension for device applications.
TL;DR: In this paper, CdS, ZnS and ZnCdS nanoparticles of various sizes (1-10 nm) were synthesized using a wet chemical route including passivation by organic capping molecules.
Abstract: CdS, ZnS and ZnCdS nanoparticles of various sizes (1-10 nm) are synthesized using a wet chemical route including passivation by organic capping molecules. The particles can also be doped with transition metal ions. The optical properties of the particles are investigated using UV absorption and photoluminescence spectroscopies. High resolution photoelectron spectroscopy using variable photon energy from a synchrotron source is performed to obtain detailed information about the nanoparticle surfaces. These investigations are able to reveal the termination of the nanoparticles and the nature of bonding between the surface atoms and stabilizing organic molecules.