Regensburg 2007 – scientific programme

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O: Fachverband Oberflächenphysik

O 60: Time-Resolved Spectroscopies

O 60.4: Talk

Thursday, March 29, 2007, 16:30–16:45, H42

Photoemission at the Si(001)-Ga surface using femtosecond lasers — Daniel Kampa, •Andrea Melzer, Jinxiong Wang, and Thomas Fauster — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen

The Si(001) (2×2)-Ga surface was used to investigate time-dependent Ga(3d) core-level shifts by pumping electrons from the valence to the conduction band. The pump-probe experiments were done by exciting the carriers with 1.59 eV laser pulses and probing the Ga(3d) core level with higher harmonics. These were generated by focussing laser pulses with 1.4 mJ energy, 30 fs pulse length and 779 nm wavelength from a multipass amplifier at a repetition rate of 1 kHz into argon. For the 25th harmonic used, the time resolution of the experiment was ∼ 400 fs after the grating monochromator. The band bending of about 110 meV of the p-doped Si(001) (2×2)-Ga surface is completely lifted by illumination of the surface with the 1.59 eV laser pulses. The Ga(3d) core level shows a slow time-dependent shift attributed to the build-up (∼ 1 ns) and decay (∼ 100 ns) of the photovoltage. The Ga(3d) core-level shift in the subpicosecond range is determined to be < 12 meV at the used pump pulse intensity of 10 mJ/cm².