Berlin 2012 – wissenschaftliches Programm
DS 35.4: Vortrag
Donnerstag, 29. März 2012, 18:30–18:45, H 2032
3h-Auger decay in the π-band of HOPG — •Matthias Richter, Daniel Friedrich, and Dieter Schmeißer — Brandenburg University of Technology Cottbus, Applied Physics and Sensors, K.-Wachsmann-Allee 17, 03046 Cottbus, Germany
In this contribution we report on the electronic structure of highly oriented pyrolitic graphite (HOPG). HOPG is a model system because of the clear separation between π- and σ-bands in the valence band regime. X-ray based measurements were done at the U49/2-PGM2 beam line at BESSYII in Berlin. The resonant photoemission spectra (resPES) at the carbon K-edge give a complete picture of the occupied and unoccupied states in these sp2 hybridized system. Above the K-edge the resPES data are dominated by the Auger process causing a C2p4 final state. The Auger lines appear at constant kinetic energy (spectator, 2h) or constant binding energy (participator, 1h). For the features right at the resonance we observe a different Auger decay mechanism. We attribute it to the decay out of an excitonic intermediate state with a long lifetime. It involves three valence hole states. The original primary core hole is filled by a normal KLL Auger decay. The excited electron rests in the excitonic intermediate state and decays later. We discuss the spectral features of such combined spectator-participator decays in detail which are found only close to resonance and only in the localized valence states of excitonic excitation i.e.C1s - 1π* transitions [1, 2, 3].  Richter et al. (2011) BioNanoScience, submitted.  Michling et al. (2011) IOP C Ser Mater Sci Eng, submitted.  Schmidt et al. (2011) Solid State Ionics, submitted.