V.S. Raju

Investigations on the chemical states of sintered barium titanate by X-ray photoelectron spectroscopy

This study describes the surface characterisation of sintered discs of polycrystalline barium titanate (BaTiO3) of different electrical properties resulting from doping with Sb5+ in different concentrations, by X-ray photoelectron spectroscopy (XPS). It involves the chemical state identification of the constituents of the ceramic and the surface contaminants. It is observed that the Ba (3d(5/2)) electron spectrum has two components with characteristic binding energies of 778.5 and 780 eV, respectively. It is indicative of the existence of Ba in two distinct chemical environments in the perovskite surfaces. Similarly, the O (1s) spectrum has two components. The component at 529.5 eV corresponds to the ceramic whereas the other at 531.4 eV is related to surface contamination. The Ba (3d(5/2)) and O (1s) spectra undergo considerable change on surface treatments such as abrasion and sputtering with AR(+) ions. In contrast, the Ti (2p(3/2)) spectrum has only one component at 457.7 eV and remains relatively unaltered on surface treatments. The relative intensity of the lower to higher energy components of Ba (3d(5/2)) spectra varies with the electrical nature of the specimens; it is about 1.15 for semi-conducting and >2 for dielectric pristine specimens, respectively. It indicates a direct correlation between the higher energy component and the semi-conducting properties of the ceramics. The abrasion of semi-conducting specimen leads to a considerable increase in the relative intensity of the higher energy component in the Ba (3d(5/2)) spectra. Them increase is more significant for semi-conducting specimens. This observation has been explained on the basis of preferred orientation of ferroelectric domains on the abraded surfaces. The analysis of C (1s) and O (1s) spectra suggests that the abraded surfaces are prone to adsorption of atmospheric contaminants. Sputter etching of the sample with Ar+ ion bombardment, apart from removing the contaminants, induces alteration in surface layers. It is manifested in the modification of Ba spectra and reduction of some Ti4+ ions to Ti3+ ions.

Characterisation of zirconium nitride coatings prepared by DC magnetron sputtering

Abstract The composition, thickness and microhardness of zirconium nitride (ZrN) coatings deposited at different nitrogen partial pressures using DC magnetron sputtering technique have been studied. Proton elastic backscattering technique involving the 14N(p,p)14N reaction has been utilised for the determination of composition and thickness of these coatings.

Compositional characterization of CrN films deposited by ion beam-assisted deposition process on stainless steel

Abstract Thin films of technologically important chromium nitride, prepared using ion beam-assisted deposition (IBAD) on stainless steel, have been characterized for their composition and thickness by backscattering spectrometry and glow discharge mass spectrometry (GDMS). The composition of the films was determined by non-resonant 14 N(p,p) 14 N backscattering using 1.6–1.73 MeV protons. The proton resonance 14 N(p,p) 14 N scattering at E p =1.74 MeV and 3 MeV α-particle backscattering were used to measure the thickness of the films. The composition and thickness of the films estimated by the GDMS method are consistent with backscattering measurements. The factors leading to the formation of the peak observed at the iron edge of the substrate in the backscattered spectra for both projectiles have been investigated.

Polyaniline, a conducting polymer, as a standard for hydrogen profiling on material surfaces

Abstract The behaviour of polyaniline, a conducting polymer, under 15N3+ ions bombardment and its subsequent utility as a standard for hydrogen estimation using the nuclear resonance reaction 1H(15N,αγ)12C have been investigated. Polyaniline withstands higher doses of radiation compared to other polymeric materials like polyethylene, polypropylene etc. used as standards for hydrogen estimation without any special sample handling arrangements.

Ion beam analysis of porous silicon layers

Abstract The composition of porous silicon layers prepared by anodising silicon in HF–methanol medium has been studied using a combination of nuclear resonance reaction analysis (NRRA) and non-Rutherford backscattering spectrometry. The 1 H ( 15 N , αγ ) 12 C resonance reaction has been used for determining depth distribution of hydrogen in the films. The distribution of other low Z elements like C, O and Si has been probed and the ratio of their atomic concentrations determined using 12 C ( α , α ) 12 C and 16 O ( α , α ) 16 O scattering. Anodisation resulted in the formation of Si1CxHy layers. The composition and thickness of the layers depend on the conditions of preparation.

Measurement of excitation functions and radiative lifetimes of oxygen ions

Oxygen ions from a 2 MV tandem accelerator have been used in beam-foil spectroscopic studies of O II, O III and O IV in the wavelength region 2000–5000 Å. Excitation functions for relative level populations in O II, O III and O IV in the incident energy range of 1.2–3.75 MeV have been measured and interpreted in terms of the independent electron model. Mean radiative lifetime measurements for a number of levels including cascades 4631 Å feeding to 2450 Å and 4344 Å feeding to 2385 Å in O IV have resulted in consistent values. Lifetime measurements for some of the O II levels of astrophysical interest have been reinvestigated and significant deviations from earlier values were observed.

Thin film characterisation using backscattering spectrometry

The use of proton resonance backscattering spectrometry for the estimation of carbon as thin films formed on a target material is discussed. Conventional He backscattering experiments were also carried out on TiVN films formed on beryllium backing but the determination of stoichiometry of these films were difficult using conventional software for depth resolution.

Determination of stoichiometry of cadmium telluride by XPS

SummaryThe stoichiometry of cadmium telluride has been determined by the non-destructive technique of XPS. The determination has been based on differential photoionisation cross-sections, electron mean free paths and areas due to M5 electrons of Cd and Te. The stoichiometry of Cd and Te determined by XPS has been found to be in good agreement with that obtained by analysing Cd and Te independently by chemical methods.