Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 38: Semiconductor substrates: clean surfaces

O 38.2: Vortrag

Dienstag, 23. März 2010, 15:15–15:30, H40

SHG Spectroscopy of Si(100)(2x1) Interband Transitions — Dominic Gerlach, Björn Braunschweig, Gerhard Lilienkamp, and •Winfried Daum — Institute of Energy Research and Physical Technologies, TU Clausthal, Leibnizstr. 4, 38678 Clausthal-Zellerfeld, Germany

It is well established that optical second-harmonic generation (SHG) at Si surfaces and interfaces with fundamental photon energies above 1.5 eV results from resonant excitation of Si interband transitions. Nevertheless, apart from the contribution due to electric-field-induced SHG in the space charge region the origin of SHG interband resonances is not well understood. We present results of the first SHG experiments on the bare Si(100)(2x1) surface with excitation of transitions for a wide range of energies. Much different to Si(100)/SiO2 systems, the SHG spectrum of the bare Si(100)(2x1) surface does not show interband excitations with energies different from the bulk-type E1 and E2 transitions. Moreover, the surface contribution to the E1 band observed for undoped Si(100)(2x1) is much stronger than that of oxidized surfaces and comparable to the bulk contribution from the space charge region of doped samples. Implications of our spectra for Si bonding at the bare and oxidized Si(100) surface are discussed.