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O: Oberflächenphysik

O 36: Postersitzung (Elektronische Struktur, Grenzfl
äche fest-flüssig, Halbleiteroberfl
ächen und -grenzfl
ächen, Nanostrukturen, Oberfl
ächenreaktionen, Teilchen und Cluster, Struktur und Dynamik reiner Oberfl
ächen)

O 36.75: Poster

Montag, 7. März 2005, 15:00–18:00, Poster TU F

Molecular dynamics simulations of Si(001) surfaces excited by fs laser pulses — •Jan van Heys and Eckhard Pehlke — Institut für Theoretische Physik und Astrophysik, Universität Kiel

The ultrafast dynamics of Si(100) surface atoms in response to strong electron-hole pair excitation by fs laser pulses has been simulated ab initio. The time-dependent Kohn-Sham equations are integrated numerically, while the atomic positions follow Ehrenfest dynamics. The adiabatic approximation is applied to the time-dependent exchange-correlation functional.

The excitation frequency has been chosen in such a way as to maximize the absorption by electronic transitions involving surface dangling-bond states. It turned out that the wave-vector dependence of the optical absorption plays a crucial role for the magnitude of electron-hole pair excitation. The effect of different laser-pulse shapes, widths, and intensities on the dynamics of the Si(001) dimer-buckling angle has been studied in detail. Notably, the magnitude of the electronic excitation as well as the buckling-angle amplitude vary non-monotonically with, e.g., laser intensity.