Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 79: Scanning Probe Techniques: STM

O 79.3: Talk

Thursday, March 19, 2015, 11:00–11:15, HE 101

Laser induced charge dynamics at the GaAs(110) surface investigated with Scanning Tunneling Microscopy — •Philipp Kloth, Katharina Kaiser, Ole Bunjes, Terence Thias, and Martin Wenderoth — IV. physikalisches Instut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen

Using optical pump probe excitation and Scanning Tunneling Microscopy we have studied the carrier dynamics at the GaAs(110) surface. We have developed a compact and convenient laser setup that provides any Tunnel Microscope with time resolution in a range from nanoseconds to microseconds. Detailed spectroscopic analysis shows that photo-excited charge carriers, trapped in a very local region beneath the STM tip, contribute to the tunneling current. By changing the bias voltage or the set point current we are able to actively select whether this optically induced tunnel channel or the common tunneling channel, present under dark conditions, dominates the overall tunneling process. This allows us to distinguish between the dynamics of inter-band recombination of the electron and hole pairs and the dynamics of the charge annihilation of the photo-excited carriers via the tunnel current.