Regensburg 2004 – scientific programme

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O: Oberflächenphysik

O 36: Hauptvortrag Weinelt

O 36.1: Invited Talk

Thursday, March 11, 2004, 14:45–15:30, H36

Dynamics of electron relaxation and exciton formation on Si(001) — •Martin Weinelt — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen, Germany

Carrier dynamics in silicon is of both fundamental and technological importance. Equally relevant as the knowledge of the bulk electronic properties is the understanding of electron dynamics at interfaces. Coupling of bulk electrons to surface or interface states can dominate electron recombination and affects device performance. The underlying electron-transfer processes occur on (sub-)picosecond timescale and can be studied following the electron dynamics after femtosecond-pulse laser excitation. Identification of the individual processes of carrier scattering, trapping and recombination requires a detailed knowledge of the surface electronic structure. The necessary comprehensive information of momentum, energy and lifetime of excited electrons is obtained by means of angle-, energy-, and time-resolved two-photon photoelectron spectroscopy. Combining this experimental approach with many-body perturbation theory the dynamics of excited electronic states at the Si(100) surface is elucidated. The recombination of hot carriers at the surface is ruled by picosecond relaxation of excited electron-hole pairs, resulting in the formation of an exciton which lives for nanoseconds.