Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 37: Scanning Probe Techniques

O 37.3: Poster

Tuesday, March 17, 2015, 18:15–21:00, Poster A

Development of a compact pulsed laser system for Scanning Tunneling Microscopy — •Terence Thias, Philipp Kloth, Ole Bunjes, and Martin Wenderoth — IV. physikalisches Instut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen

Pulsed laser excitation in STM allows resolving processes on surfaces beyond the bandwidth of the current amplifier. A major challenge of optical excitation in STM is controlling the influence of thermal effects. We implemented a sub-micrometer precise stage that allows the scanning of the focus point of the laser beam along the tip-surface junction - even during tunnel conditions. Thereby we assure to find the spot of maximum excitation in a standardized manner guaranteeing reproducible conditions. To keep the thermal power at the tip constant, standard pump-probe pulses must be transformed into complex laser pulse patterns [1]. We have developed a compact and convenient laser setup that can be added to any STM with optical access to the sample surface. Using an optical modulator with a bandwidth in the gigahertz range and a high frequency function generator, we process a continuous wave laser beam into nanosecond pulses. By generating pulse series exclusively in an electronic way we can easily adapt parameters like pulse width or repetition rate to the demands of the experiment. [1] Terada et al., Nature Photonics, 4(12), 2010.