Armin Meisel

Auger parameters and relaxation energies of phosphorus in solid compounds

Abstract The 1s, 2s and 2p photoelectron binding energies and the KL 2,3 L 2,3 ( 1 D 2 ) Auger electron energies of phosphorus in 28 solid compounds have been measured using a mixed X-ray source (Al—Ag). The modified Auger parameters, α, are presented in two-dimensional chemical state plots. Extra-atomic static relaxation energies have been calculated using Auger parameters ξ.

X-ray photoelectron spectroscopic core level shifts of phosphorus in phosphates and native oxide layers on InP(100). Applications of the Auger parameter concept

Abstract Solid phosphorus compounds have been investigated by X-ray photoelectron spectroscopy (XPS) and X-ray Auger electron spectroscopy. The core level shifts have been separated into initial and final state shifts by employing the Auger parameter concept. Although strong chemical trends in general dictated the shifts, the significant differences between compounds with fourfold oxygen coordination could essentially be attributed to environmental effects. We have been able to demonstrate that the extra-atomic or environmental contributions to the shifts of relaxation and initial state terms may be semiquantitatively estimated by dielectric screening and the Madelung potential models, respectively. The investigations were extended to native oxide layers on InP(100). The chemical state plots have been found to provide information on the nature of the layers beyond a conventional XPS analysis. In a similar way to that for bulk samples, the initial state-related shift contributions indicate the condensation of phosphates in the layers, and the Auger parameter shifts are sensitive to the composition of the layers and to substrate screening.

Investigation of soft X-ray emission and K-edge absorption spectra of V2O5 and LixV2O5 electrodes

The investigation of electrode materials based on Li-V2O5/MoO3 was performed by V Lα soft X-ray emission, V K-absorption, and photoelectron spectroscopies. During the discharge process lithium is inserted into the electrodes accompanied by a surface enrichment of LiO− groups. As the X-ray absorption spectrum obtained by excitation with synchrotron radiation, the emission band recorded with a laboratory spectrometer is also sensitive to reduction processes of the vanadium atom and to changes of bond lengths in the first coordination sphere.

Soft X-ray photoelectron spectroscopy studies of the initial oxidation of AlxGa1−xAs(100) surfaces

Core level shifts and intensity ratios of the spectra of Zr Mζ excited photoelectrons were used to describe the oxide growth on AlxGa1−xAs(100) surfaces with different x values. The chemisorption of oxygen at exposures up to 109 L was studied at room temperature. In highly surface sensitive experiments (λ ⋍ 0.6 nm) we could show that oxygen interacts first with the aluminium atoms. During the further oxidation an outdiffusion of aluminium takes place leading to the formation of a surface aluminium oxide layer which hinders the oxidation of the other semiconductor elements.

XPS satellite structure of nickel complex compounds as an analytical tool for studies of ground state properties

Abstract Reliability of iterative EHT method to reproduce (i) the energy and the atomic character of electronic molecular states of large nickel complex compounds, (ii) the energy separation between main Ni 2p photoeleotron line and satellites, and (iii) their relative intensities is studied comparing EHT data and SCF-DV-Xα results with experimental Ni Lα and S Ks X-ray emission bands and Ni 2p Apectra. The results of EHT calculations applying Larssons charge-transfer concept suggest meaningful relationship between satellite parameters and electronegativity in NiX n± 6 ions contrary to a more complex correlation due to back bonding and charge delocalization in large chelate systems.

The Relaxation of Photoelectron and Auger Energies in Solid Phosphorus Compounds

Relaxation energies, recently published by Franke et al. [13] will be discussed together with physical and chemical quantities, related to the properties of the initial and final state of the photoemission process in solid phosphorus compounds. Nearest neighbour contributions and effects of higher coordination spheres on core hole screening have been identified by comparison to molecules and systematic variations of the environment in solids. A local approach to the polarization energy has been successfully applied to predict the nearest neighbour effects in polar-covalent compounds. Contributions from second and higher coordination of the photoinized atom are reasonably reflected in the dielectric model using macroscopic quantities. Correlations of extraatomic relaxation to gap energies and electronegativities of the chemical environments are reported for phosphorus compounds and will be addressed qualitatively to dielectric and ground state properties.