Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 50: Time-resolved spectroscopy II
O 50.2: Vortrag
Freitag, 31. März 2006, 11:30–11:45, WIL C207
Electronic Structure of Si(100) at high excitation density: A Time-Resolved Photoemission Study with Combined Laser and Synchrotron Radiation. — •H. Prima Garcia1, T. Giessel1, R. Schmidt1, R. Weber1, W. Widdra2, and M. Weinelt1,3 — 1Max-Born-Institute, Berlin, Germany. — 2Martin Luther University, Halle, Germany. — 3Freie university, Berlin, Germany.
We have studied the dynamics of laser-induced plasma-driven
processes at the Si(100) surface. At the BESSY low-α hybrid
mode we established an overall time-resolution of 10 ps.
For 800 nm, 60 fs laser pulses induces an e-h plasma density of
1021 cm−3 and concomitant band gap narrowing in the bulk.
Band gap renormalization occurs in 50 picoseconds and is
distinguishable from photovoltage dynamics.
We observe in addition depopulation of the Dup surface state
by more than 40%, which suggests a sizeable change of the
surface electronic structure and a corresponding reduction of the
dimer buckling. A recent time-dependent DFT study predicts this to
occur on a subpicosecond time-scale [1].
Si 2p core level spectra show a transient increase of the
linewidth, with the surface component broadening stronger than the
bulk component. This is interpreted in terms of screening induced defect formation
due to the high and long-lived transient carrier density at the
surface upon IR laser excitation.
[1] Jan van Heys, Michael Lindenblatt, and Eckhard Pehlke, Phase transitions.in.press.00.May.2005)