Dresden 2006 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

O: Oberflächenphysik

O 29: Poster session II (Nanostructures, Magnetism, Particles and clusters, Scanning probe techniques, Time-resolved spectroscopy, Structure and dynamics, Semiconductor surfaces and interfaces, Oxides and insulators, Solid-liquid interfaces)

O 29.56: Poster

Mittwoch, 29. März 2006, 14:30–17:30, P2

TDDFT simulation of Si(001) dimer excitation by intense fs laser-pulses — •Eckhard Pehlke and Jan van Heys — Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität Kiel, 24098 Kiel

The surface band-structure of the Si(001) surface is characterized by either fully occupied or fully unoccupied dangling-bond orbitals located at the Si-dimer atoms. The population dynamics of the initially unoccupied states after laser excitation and the surface response has been studied by Weinelt et al. [1]. Here we present simulations of the dynamics of the Si(001) surface atoms, in particular the dimer-buckling angle, after very strong electron-hole pair excitation in the surface states by an intense fs laser-pulse. The dynamics of the electrons is described within time-dependent density functional theory while the nuclei follow classical Ehrenfest dynamics. The electric field representing the laser excitation is restricted to the direction perpendicular to the surface. Different laser-pulse shapes and intensities have been studied. The buckling angle decreases on a timescale of about 150 fs. A coupling between the dimer buckling angle and the total number of excited electrons is observed. Initial state contributions to the time-dependent surface core-level shifts have been calculated (screening effects, however, are still lacking). Additionally, the lifetime of the induced surface-atom vibrations has been investigated by molecular dynamics simulations on the Born-Oppenheimer surface.

[1] M. Weinelt et al., Phys. Rev. Lett. 92, 126801 (2004) and Appl. Phys. A 80, 995 (2005).