Paper AS-WeM4
Some Problems of Quantitative Applications of High (up to 15 keV) Energy X-ray Photoelectron Spectroscopy
Wednesday, November 11, 2009, 9:00 am, Room C2
X-ray photoelectron and Auger spectroscopy, using hard X-rays for excitation and high energy resolution (HAXPES), due to the availability of the 3rd generation synchrotrons and advanced electron spectrometers, has shown a spectacular development recently allowing to utilize its non-destructive capability for providing a deeper insight into the bulk electronic structure of solids and the chemical composition of buried layers and interfaces lying at depths of several tens of nm. Quantitative analytical applications of HAXPES e. g. for studies of materials with new, important functions and complex physical, electronic and chemical structure are highly desired, however, some conditions are significantly different compared to the case of the conventional XPS. Although surface excitations and elastic electron scattering are playing a smaller role at higher electron energy and the inelastic background becomes less important, the low photoionization cross sections request a careful design of the experiments, non-dipole effects influencing the angular distribution of photoelectrons are non-negligible and effects of atomic recoil should be taken into account in the case of low atomic number components when looking at chemical shifts or energy broadening of core photoelectron lines. In addition, the available data for parameters (e. g. parameters characterizing electron transport in solids in the 2-15 keV electron energy range) necessary for quantitative chemical analysis using HAXPES are rather sparse and our present knowledge is limited concerning the role of intrinsic (core hole induced) excitations. In this contribution the magnitude and the energy dependence of physical parameters (derived from experiment or estimated using model calculations) relevant for quantitative applications of HAXPES are discussed together with new experimental data and simple models proposed for describing high energy photoinduced electron spectra. Acknowledgements: The support of the HASYLAB/DESY and the European Community under Contract RII3-CT-2004-506008 (IA-SFS) as well as by the Hungarian project OTKA 67873 is gratefully acknowledged.