Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 3: New Methods and Developments I: Scanning Probe Techniques

O 3.10: Vortrag

Montag, 1. April 2019, 12:45–13:00, H5

Near-field driven photo-assisted Scanning Tunneling Microscopy — •Benjamin Schröder1, Ole Bunjes1, Lara Wimmer1, Katharina Kaiser2, Martin Wenderoth1, and Claus Ropers11Georg-August-Universität, IV. Physikalisches Institut, Friedrich-Hund-Platz 1, 37077 Göttingen — 2IBM Forschungslabor, Säumerstrasse 4, 8803 Rüschlikon

Recent developments in Scanning Tunneling Microscopy (STM) pave the way towards a controlled optical excitation of the tunnel junction with ultrafast laser pulses. This promises the local observation of surface dynamics, including photochemical reactions, phase transitions and optical manipulations of surface defects on the atomic scale.
Here, we combine an ultra-high-vacuum low-temperature STM with femtosecond laser excitation. The laser is focused directly into the tunneling junction formed by a gold tip and a Cu(100) surface. The strongly enhanced optical near field in the vacuum gap results in an additional photocurrent, evident by comparing current-distance measurements with and without laser illumination. Specifically, current-distance dependencies exhibit a contribution with a spatial decay length about ten times larger than for regular tunneling.
We employ a one-dimensional model to extract an effective energy distribution of tunneling electrons from the experimental data. We discuss contributions from multiphoton excitation and hot electron tunneling.
This project is financially supported by the DFG in the SFB 1073 (project C4).

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