Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 63: Posters: Scanning Probe Methods

O 63.19: Poster

Mittwoch, 2. April 2014, 17:30–21:00, P2

Laser induced Time Resolved Scanning Tunneling Microscopy — •Philipp Kloth, Christian Werner, Karen Teichmann, and Martin Wenderoth — IV. physik. Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen

We present a detailed description of a combined setup of a pulsed laser source and a Scanning Tunneling Microscope (STM) in Ultra High Vacuum. The most demanding issue of light excitation in STM is the handling of thermal effects. For time resolved operation this challenge results in a transformation of standard pump-probe pulses into complex laser pulse patterns. Triggered by the groundbreaking results of Shigekawa [1] our intention was to develop a setup with a stronger focus on the flexibility.

We generate pulsed laser light in a pure electronic way. A diode laser in combination with a high-bandwidth electro-optical modulator produces light excitation from continuous-wave mode to single nanosecond pulses. The voltage pulses are supplied by a commercial function generator. This allows to adapt the pulse pattern exactly to the timescale needed in the experiment.

Results on the GaAs(110) surface show a huge impact on the spectroscopic properties due to the light excitation. Electron-hole pair generation is not only affecting the always present charge region in the sample but also opens new tunnel channels resulting in extra current. Time resolved studies allow to probe these processes individually revealing characteristic decay constants in the nanosecond regime.

[1]Terada et al., Nature Photonics, 4(12), 12 2010.