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O: Fachverband Oberflächenphysik

O 78: Nanostructures at Surfaces IV: Various Aspects

O 78.1: Talk

Thursday, March 10, 2016, 10:30–10:45, S052

Charge dynamics at semiconductor surfaces investigated with time-resolved Scanning Tunneling Microscopy — •Philipp Kloth, Katharina Kaiser, Terence Thias, and Martin Wenderoth — IV. physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany

An overview on the combination of optical excitation and Scanning Tunneling Microscopy (STM) for studying the carrier dynamics at the GaAs(110) surface is given. In this system the tip-induced electric potential is very sensitive to the charge configuration composed of locally fixed dopants and ambipolar optical excited free carriers present at the surface. A detailed spectroscopic analysis [1] has shown that photo-excited charge carriers, trapped in a very local region beneath the STM tip, contribute to the tunneling current. By adjusting the current in a controlled manner we are able to actively access different screening conditions of the electric potential at the surface. Depending on the dominant tunneling channel, pump-probe excitation can resolve different recombination processes of charge in the nanoscaled Space Charge Region. By using the lateral resolution of the STM, the influence of single dopants on the relaxation dynamics of the system is investigated. We discuss the impact of these charged and surface-sided defects in terms of their varying binding energy [2] in comparison to conventional bulk-positioned donors.

[1] Kloth et al., Nat. Comm. (2015) [2] Teichmann et al., PRL (2009)