Regensburg 2016 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 71: Scanning Probe Techniques and New Experimental Methods

O 71.5: Poster

Mittwoch, 9. März 2016, 18:15–20:30, Poster A

Combining Scanning Tunneling Microscopy and pulsed optical excitation — •Judith von der Haar, Philipp Kloth, Terence Thias, Ole Bunjes, and Martin Wenderoth — IV. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen

The combination of Scanning Tunneling Microscopy (STM) and optical excitation merges two of the most successful experimental techniques in solid-state physics. Especially pump-probe excitation gives the prospect to resolve surface dynamics on the atomic scale. A serious challenge of optical excitation in STM is controlling the thermal load at the tunnel junction. We present a very compact and versatile laser setup that addresses various requirements of this experimental technique. First of all, the laser source must provide a very low-noise and stable output power. Next, in order to find the spot of maximum excitation in a standardized manner, it is important to implement 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. At last, standard pump-probe pulses must be transformed into complex laser pulse patterns [1]. Using an optical modulator with a bandwidth in the gigahertz range and a high frequency function generator, we process the continuous wave laser beam into nanosecond pulses. [1] Terada et al., Nature Photonics, 4(12), 2010.