L. Kövér

The role of oxide layer formation during corrosion inhibition of mild steel in neutral aqueous media

Abstract The influence of phosphonic acid with Ca cation on iron surfaces in neutral aerated media (0.5 mol dm − NaClO 4 ) has been studied by electrochemical and surface analytical methods. X-ray induced photoelectron (XPS) and Auger electron spectroscopy (XAES) provided the possibility for identification of different chemical states of the constituents of the corrosion protective layers. The presence of certain cations led to a synergistic effect. It was found that calcium ions were incorporated into the film that developed on the mild steel surface, containing a mixed oxide and hydroxide complex. Electrochemical Impedance Spectroscopy (EIS) was used to determine the inhibitor efficiency of phosphonic acid at different concentrations. The data obtained were fitted and modelled by an equivalent circuit model.

High-Resolution Photoemission and Auger Parameter Studies of Electronic-Structure of Tin Oxides

The electronic structure of metallic Sn, polycrystalline Sn oxides, and (110) natural single crystal SnO2 (cassiterite) was studied by high resolution measurements of core and valence photoemission, photoinduced Auger spectra, and energy loss spectra. The advantage of in vacuo scraping in obtaining SnO surfaces is shown in comparison with surface cleaning by ion sputtering. Valence band x‐ray photoemission spectroscopy spectra are interpreted by a cluster‐type discrete variational Xα molecular orbital model, revealing the change in the electronic structure which leads to an increased conductivity. The use of the Auger parameter approach in gaining information on the initial and final state effects, ligand polarizability, and final state hole–hole repulsion energies are demonstrated for the case of tin oxides.

The effect of calcium ions on the adsorption of phosphonic acid: a comparative investigation with emphasis on surface analytical methods

Abstract The influence of calcium ions on the adsorption of 1-hydroxy-ethane-1,1-diphosphonic acid (HEDP) on Fe electrodes has been examined. Surface analytical methods (XPS and XAES) have been applied in order to obtain direct information on the structure of the surface layer. On the surfaces of electropolished samples, various Fe 2+ , Fe 3+ and FeOOH compounds as well as the metallic state of Fe could be identified in the surface layers. HEDP was adsorbed on the iron surface in almost the same extent, when the basic solutions were bidistilled water or 0.5 mol dm −3 NaClO 4 , respectively. The presence of Ca 2+ cations increased the quantity of phosphonate adsorbed on the metal surface considerably. Varying the Ca/HEDP molar ratio in the solution between 0.5 and 4.0, the Ca/HEDP molar ratio on the metal surface remained under a limit close to one, corresponding to what could be expected on the basis of the results obtained by radiotracer method.

The KLL and KLM Auger spectra of 3d transition metals, Z = 23–26

Abstract High resolution (1.0–1.6 eV) X-ray excited KLL and KLM Auger spectra and the respective Auger parameters of V, Cr, Mn and Fe, obtained from thin metallic layers, are reported. The corresponding experimental (Auger) transition energies (the first high resolution experimental data except for Mn) and relative Auger intensities are compared with data obtained earlier following electron capture in the decay of radioactive isotopes, and also with available theoretical estimates. Differences in the surface chemical states of the samples and in the methods applied for evaluation of the spectra could explain the considerable deviations between the two sets of experimental results, rather than differences in the Auger process following photoionization and electron capture. The number of Auger transitions identified in the KLL spectra shows the applicability of the intermediate coupling model for these cases.

Monte Carlo modelling of the backscattered electron spectra of silver at the 200 eV and 2 keV primary electron energies

Abstract The electron energy distribution of the backscattered electrons from a polycrystalline silver sample was studied in the direction of the surface normal of the specimen, at the 200 eV and 2 keV energy of the primary beam. The angle of the incident electron beam was 50° with respect to the surface norm. For simulation of the backscattered electron energy distributions the Monte Carlo technique was used and the computed spectra were compared to the measured reflected electron spectra in the energy range of few times 10 eV from the elastic peak. The probable reasons of the observed discrepancies between the measured reflected electron energy loss spectra and the calculated spectra are discussed. In addition, the yield of the backscattered electrons as a function of the number of elastic and inelastic collisions is compared for different parts of the backscattered electron spectra.

A distorted field cylindrical mirror electron spectrometer: I. Calculation of the analyzer

Abstract A new “box” type cylindrical mirror electrostatic analyzer (CMA) with second order focusing properties is presented. The effect of the fringing field was taken into consideration in the design, resulting in some advantage (e.g. better dispersion) compared to the classical CMA.

KLL Auger transitions in metallic Cu and Ni

Abstract The X-ray excited KLL Auger spectra of polycrystalline Cu and Ni films, measured with high energy resolution and presented here, show intensive satellite structures of intrinsic origin. A good agreement is between the determined relative KL 23 L 23 energies or KL 3 L 3 relative intensities and their experimental (Cu) and theoretical (free atoms) values obtained earlier. However, the deviation is significant for the absolute Auger transition energies and very large for the relative intensity of the Ni KL 2 L 2 ( 1 S 0 ) line or of the initial state shakeup satellites.

Line shape analysis of high energy X-ray induced Auger- and photoelectron spectra of thin Cu and Ni films

Abstract A detailed study of the line shape of high energy Cu X-rays excited Auger- and photoelectron spectra of layered samples is presented. The samples consisted of polycrystalline Cu and Ni overlayers of various thicknesses deposited on a Si substrate. The raw data show that the contribution caused by bulk inelastic scattering in the spectra increases significantly with overlayer thickness. Employing a general deconvolution procedure, the contribution of bulk inelastic scattering was consistently eliminated. The resulting spectra are in excellent agreement. The contribution caused by surface excitations has a very moderate effect at these high energies, while intrinsic losses were estimated to make up ∼30–50% of the total intensity. The true energy distribution at the source as seen by the spectrometer was established by elimination of the features due to surface excitations and the contribution from intrinsic excitations of the delocalized electronic states was determined.

Determination of the inelastic mean free path of electrons in polythiophenes using elastic peak electron spectroscopy method

Abstract The inelastic mean free path (IMFP) is an important parameter for quantitative surface characterisation by Auger electron spectroscopy, X-ray photoelectron spectroscopy or electron energy loss spectroscopy. An extensive database of the IMFPs for selected elements, inorganic and organic compounds has been recently published by Powell and Jablonski. As it follows from this compilation, the published material on IMFPs for conductive polymers is very limited. Selected polymers, such as polyacetylenes and polyanilines, have been investigated only recently. The present study is a continuation of the research on IMFPs determination in conductive polymers using the elastic peak electron spectroscopy (EPES) method. In the present study three polythiophene samples have been studied using high energy resolution spectrometer and two standards: Ni and Ag. The resulting experimental IMFPs are compared to the respective IMFP values determined using the predictive formulae proposed by Tanuma and Powell (TPP-2M) and by Gries (G1), showing a good agreement. The scatter between the experimental and predicted IMFPs in polythiophenes is evaluated. The statistical and systematic errors, their sources and the possible contributions to the systematic error due to influence of the accuracy of the input parameters, such as the surface composition and density, on the IMFPs derived from the experiments and Monte Carlo calculations, are extensively discussed.

Origin of the satellites in the high resolution KLL Auger spectra of the 3d metals, Cu and Ni, and their alloys

The understanding of the structure of high energy Auger spectra in metals and alloys of practical interest is relevant for studying solid state effects on core potentials, charge transfer and localization in these systems. In previous work evidence was found for the presence of intrinsic satellites in the LMM Auger spectra of 4d metals. Here we report the results of a study of the satellite structure identified in the high resolution KLL spectra of 3d metals Cu, Ni and some of their alloys. KLL spectra excited by Cu X-rays from polycrystalline Cu, Cu-noble metal and Ni-Fe alloy samples, were measured by a high luminosity hemispherical electron spectrometer. The satellite structures revealed in the spectra are compared to the structures obtainable on the basis of the spectator vacancy model. For the case of these metals and alloys, our results show that the KLL satellites can be attributed to intra-atomic 3d shake-up processes.