Regensburg 2004 – scientific programme

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O: Oberflächenphysik

O 14: Postersitzung (Adsorption an Oberflächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Phasenübergänge, Rastersondentechniken, Struktur und Dynamik reiner Oberflächen)

O 14.52: Poster

Monday, March 8, 2004, 18:00–21:00, Bereich C

Ultrafast dynamics of the Si(001) surface after electronic excitation — •Jan van Heys and Eckhard Pehlke — Institut für Theoretische Physik und Astrophysik, Universität Kiel

Due to the strong Jahn-Teller coupling between the buckling angle and the electronic structure of the dimers on the Si(001) surface, this surface represents a promising model system for studying ultrafast surface atomic motion in response to electronic excitation. Depending on excitation density, due to the creation of electron-hole pairs in the dangling-bond surface-states the energy preference for buckled dimers as opposed to symmetric dimers can be nearly lost.

We present first results from ab initio molecular dynamics simulations of the non-adiabatic motion of the electrons and ions at the Si(001) surface after strong electronic excitation. Electrons are described within the time-dependent density functional theory while the motion of the ions follows from classical Ehrenfest dynamics.

We find that, provided the excitation exceeds order of 1/2 electron per dimer, the buckling angle flips on a timescale of about 150 fs.