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O: Fachverband Oberflächenphysik

O 79: Electronic structure II

O 79.7: Vortrag

Donnerstag, 17. März 2011, 16:30–16:45, WIL C107

Energetics and dynamics of hot electrons at GaP and InP surfaces — •Philipp Sippel, Robert Schütz, Klaus Schwarzburg, Thomas Hannappel, and Rainer Eichberger — Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany

The surface electronic structure and dynamics of hot electrons was investigated for InP(100) and GaP(100) samples with time-resolved 2PPE (TR-2PPE). The In- and Ga-rich grown surfaces were prepared via metal organic chemical vapour deposition, exhibiting (2x4) reconstruction checked by in-situ reflectance anisotropy spectroscopy. The samples were transferred to the experimental setup with a contamination-free UHV commuting system. TR-2PPE spectroscopy was used, applying laser pulses of 40fs duration. The technique allowed for detection of surface states for this GaP(100) reconstruction and a comparison with the similar surface electronic structure of InP(100) was made. For InP, the dynamics of unoccupied surface states was studied, varying excitation energies. Using 4.66eV pump-photons, we excited hot electron bulk states and observed subsequent filling of surface states by scattering of electrons. Furthermore, we excited electrons from the valence band to bulk levels that were isoenergetic with the well known C2 surface state. This energy also corresponds to a potential excitation scheme, involving a direct optical transition from an occupied surface state (V1) to C2. Since we could not observe a noticable magnification of the surface state peak in the photoelectron spectra, we assume that this resonant transition is not allowed.