Regensburg 2007 – scientific programme
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O: Fachverband Oberflächenphysik
O 44: Poster Session II (Semiconductors; Oxides and Insulators: Adsorption, Clean Surfaces, Epitaxy and Growth; Surface Chemical Reactions and Heterogeneous Catalysis; Surface or Interface Magnetism; Solid-Liquid Interfaces; Organic, Polymeric, Biomolecular Films; Particles and Clusters; Methods: Atomic and Electronic Structure; Time-resolved Spectroscopies)
O 44.48: Poster
Wednesday, March 28, 2007, 17:00–19:30, Poster C
Unbuckling dimers at the Silicon(100) surface — •Christian Eickhoff1,2, Cornelius Gahl1, Tanja Giessel1, Jens Kopprasch1,2, Irina Ostapenko1, Helena Prima Garcia1, Roland Schmidt1,2, and Martin Weinelt1,2 — 1Max-Born-Institut, Max-Born-Straße 2A, 12489 Berlin — 2Freie Universität Berlin, Arnimallee 14, 14195 Berlin
Electronic structure and electron dynamics at the
Si(100) surface have been studied by means of time-resolved
photoemission spectroscopy. For low IR pump-laser intensity, i.e.
in the limit of single-electron dynamics, electrons excited to the
Ddown dangling-bond band decay exponentially with a lifetime
of ≃ 200 ps. At larger excitation densities the decay rate
scales quadratically with the population which indicates an
effective phonon- and/or defect-assisted surface recombination
between the occupied and unoccupied Dup and Ddown
dangling-bond bands. Having established significant depletion of
the Dup and corresponding population of the Ddown-bands,
we observe spectroscopic signatures of atomic motion of the
buckled dimers at the Si(100) surface. Time-dependent density
functional theory predicts this electronically driven motion to
occur on a femtosecond time-scale and to effectively lift the
ground-state Peierls distortion of the buckled silicon dimers [1].
[1] J. van Heys, M. Lindenblatt, and E. Pehlke, Phase Transitions 78, Nos. 9-11 (Sept.-Nov. 2005), 773-786