Regensburg 2007 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 26: Metal-Insulator Transition
TT 26.13: Talk
Thursday, March 29, 2007, 17:15–17:30, H19
Unexpected line shapes and Cross Section Effects in Hard X-ray Photoelectron Spectroscopy of transition metal oxides — •T.C. Koethe1, Z. Hu1, C. Schüßler-Langeheine1, J. Gegner1, C.F. Chang1, G. Panaccione2, F. Offi3, and L.H. Tjeng1 — 1II. Physikalisches Institut, Universität zu Köln — 2TASC, Trieste, Italy — 3Dept. Physics, University Rome III, Italy
The recent progress in Hard X-ray Photoelectron Spectroscopy (HXPES) has facilitated access to bulk sensitive spectroscopic information that was previously unavailable. The large kinetic energies of photoelectrons in HXPES yield inelastic mean free paths of the order of 100 Å, thus providing essentially bulk sensitive results. In this respect, HXPES is an important improvement over standard photoemission in the soft x-ray or UV range having considerable surface contribution to the spectra. For correlated systems, this surface sensitivity is particularly problematic due to the possibly strong modifications of the electronic structure at the surface of these systems. We have investigated a number of simple transition metal (TM) oxides in order to study the effects of variations in the photoionization cross sections for high photon energy spectra. We find that the line shapes of the valence band spectra are strongly modified as compared to lower photon energy results. In particular, we observe strongly enhanced contributions of the TM 4s which are two orders of magnitude more intense than in the soft x-ray regime. These results are of importance for the conception and interpretation of HXPES in correlated systems.