X-ray photoelectron spectroscopic studies on pyrolysis of thin films of plasma-polymerized acrylonitrile

X-ray photoelectron spectroscopy is used to elucidate the chemical environments of the atoms in as-deposited plasma-polymerized acrylonitrile (PPAN) thin film and PPAN films pyrolysed at the temperatures 573 and 773 K. The photoelectron spectra are collected at the electron take-off angles of 20° and 70°. The C 1s, N 1s, and O 1s spectra of all the samples demonstrate clearly that the structural modifications take place owing to pyrolysis in the PPAN structure. Apart from the structural modifications, a decrease of nitrogen and an uptake of oxygen are evidenced. A few chemical species other than the usual ones are also detected.     

X-ray photoelectron spectroscopic studies of carbon fibre surfaces

Carbon fibres were anodically surface treated by passing them continuously through an electrochemical bath, thus simulating a possible industrial surface-treatment process. Composites were made from these fibres with an epoxy resin and their interlaminar shear strength (ILSS) tested. The surfaces of the fibres were examined by X-ray photoelectron spectroscopy after treatment. Both golvanostatic and potentiostatic cell control led to treated fibres that produced composites with high interlaminar shear strengths (80 to 90 MPa). The effect of potential, reaction time, electrolyte and subsequent heating of the fibres in a vacuum on the ILSS of the composites is reported. The rise in ILSS with surface treatment is not dependent upon the O-1 s: C-1 s ratios or the amount of carboxyl functionality present on the surface. This suppors the view that mechanical keying of the resin to the fibre surface plays an important role in forming the fibre-resin bond.     

X-ray photoelectron spectroscopic studies of partially coked HZSM-5 catalysts

XPS studies of partially coked HZSM-5 catalysts have been carried out. As a result of the coke deposition Si(2s) and O(1s) binding energies were decreased by 1.0 eV due to the electron charge transfer from the coke to the framework atoms. The electron energy loss peaks were observed for Si(2s) of coked HZSM-5 catalyst. The results suggest that the coke was deposited on SiO₄ tetrahedra.     

X-ray photoelectron spectroscopic studies of flux grown CsMnFeF6 single crystals

This letter is a dedication to Professor R. Srinivasan, Department of Crystallography and Biophysics, University of Madras, on his sixtieth birthday.     

The optical properties of sprayed CdS thin films

In the study presented in this paper we attempted to interpret the reflectance and the transmittance of sprayed CdS films. Assuming a model based on multilayer film theory we showed that sprayed CdS film is a combination of multilayer stacks of crystallites and gaseous inclusions.     

Auger and X-ray photoelectron spectroscopic depth profiling techniques applied to ultra-thin titanium films

Auger electron spectroscopy and X-ray photoelectron spectroscopy in combination with sputter profiling techniques were employed to study ultra-thin (100–500 Å) titanium films. The composition of the films was studied as a function of substrate, deposition temperature and heating. Particular attention was given to the interfacial region.The data indicated that the films were a mixture of titanium and TiO₂. At no point was a pure titanium phase present. At a deposition temperature of 450°C the interface was composed of titanium, TiO₂, silicon and SiO₂ when quartz was the substrate and titanium, TiO₂, aluminum and Al₂O₃ when sapphire was the substrate. The silicon and aluminum resulted from reduction of the substrate. When the deposition temperature was approximately 25°C the reductive interaction was minimized.     

Photoacoustic and X-ray photoelectron spectroscopic studies in reduced lead zirconate titanate ceramics

Lead zirconate titanate (PZT) is known to become a semiconductor after reduction in a hydrogen atmosphere. An attempt is made here to characterize the reduced, as well as the unreduced, PZT system with the help of photoacoustic (PA) spectroscopy and X-ray photoelectron spectroscopy (XPS) and to obtain useful information regarding its electronic behaviour.The band gap of the unreduced PZT is estimated to be 3.56 eV from PA spectra which is observed to remain unaffected after doping with lanthanum, niobium and strontium. XPS results indicate the presence of metallic lead in PZT after hydrogen reduction whereas other elements remain unaffected. This becomes responsible for the change in its conductivity and also for the increased absorption in the visible range which is reflected in the PA spectra. The electronic structure based on PA spectra is also presented for the reduced and unreduced PZT systems.     

An electrochemical study of sprayed CdS and CdZnS films

Thin films of cadmium sulphide and cadmium zinc sulphide were prepared by the airless spray method. Their electrical and optical properties were studied using photoelectrochemical techniques. The films showed a very high donor concentration (N_D ≈ 10¹⁷) irrespective of the ZnS content. Thermal treatments decreased this concentration. The addition of a copper salt to the sprayed solution improved the crystalline quality of the film but did not change the values of N_D. The band gap energies of the films were in good agreement with those reported for evaporated films of similar compositions.     

X-ray photoelectron spectroscopic analysis of barium-labelled carbon fibre surfaces

A technique for labelling acidic functional groups on carbon fibre surfaces with barium has been developed for X-ray photoelectron spectroscopy analysis of the surface acidity of commercial Type II fibres, with differing degrees of oxidation. As the dibasic barium is believed to label adjacent monobasic groups, the results show that up to 58% of the surface oxygen, on the commercially treated fibres, is present in the acidic form.     

Mössbauer and X-ray photoelectron spectroscopic studies of heat-treated calcium borate glasses containing iron

⁵⁷Fe Mössbauer and X-ray photoelectron spectroscopic studies have been carried out on a number of iron-containing calcium borate glasses which show large changes in d.c. conductivity upon annealing. The Mössbauer spectra of the unannealed glass samples are compatible with the presence of predominantly ferric iron in a six-co-ordinate oxygen environment. Upon annealing a partial ordering of the glassy phase is found as indicated by a reduction in the linewidth of the Mössbauer resonances. Longer annealing times lead to the precipitation ofα-Fe₂O₃ clearly identified by the gradual appearance of a six-line magnetically split pattern in the Mössbauer spectra. These changes are qualitatively correlated with changes in d.c. conductivity of the samples. The binding energies and full width at half maxima of representative core levels of each element present show a remarkable consistency for all samples. Moreover the 2p spectra of iron incorporated in the glassy phase are essentially similar to that of the precipitated Fe₂O₃.     

X-ray photoelectron spectroscopic studies of evaporated V2O2and co-evaporated V2O5/B2O3 films

X-ray photoelectron spectra of evaporated V₂O₅ and co-evaporated V₂O₅/B₂O₃ thin films have been investigated. The photoelectron spectrum of a simple V₂O₅ film shows the splitting of the V 2p level in accordance with the spins. The values of binding energies corresponding to V 2p and O1s are comparable with those reported previously. For co-evaporated V₂O₅/B₂O₃ films a chemical shift in the O 1s level has been observed which has been attributed to the changed chemical environment of oxygen as a result of the presence of boron and vanadium atoms. The values of binding energies for V 2p_3/2 and O 1s corresponding to simple evaporated V₂O₅ and co-evaporated V₂O₅/B₂O₃ show the presence of V₂O₄ species in the films.     

Cubic CdS thin films studied by spectroscopic ellipsometry

CdS polycrystalline films were grown onto glass substrates by chemical bath deposition (CBD) and characterized by spectroellipsometry, X-ray diffraction and transmission electron microscopy. The X-ray diffraction patterns of the samples showed the presence of a CdS cubic phase (β-CdS) and of Cd2SiO4 as interfacial material. Using electron diffraction it was possible to index the films as cubic CdS. From effective dielectric function measurements and from reported optical data for the dielectric function of cubic CdS crystals, grown by vapour phase epitaxy, it was possible to fit the experimental data to an effective medium approximation, and to deduce the film thickness, the void fraction and the field screening. This revised version was published online in August 2006 with corrections to the Cover Date.