Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 47: Poster Tuesday: Scanning Probe Techniques

O 47.7: Poster

Dienstag, 2. April 2019, 18:00–20:00, Poster D

Modelling Photo-Assisted Scanning Tunneling Microscopy — •Ole Bunjes, Benjamin Schröder, Lara Wimmer, Claus Ropers, and Martin Wenderoth — Georg-August-Universität, IV. Physikalisches Institut, Friedrich-Hund-Platz 1, 37077 Göttingen

Scanning Tunneling Microscopy (STM) offers unique capabilities in imaging and spectroscopy on the atomic scale. A promising approach to observe surface dynamics faster than electronic sampling speeds is the combination of STM with pulsed laser excitation.
Typically, the tunnel current I(z) depends mono-exponentially on the tip-sample distance z. In recent experiments, we found a strong deviation from this typical exponential decay upon femtosecond laser illumination of the tunnel junction.
We explain this observation by modelling the vacuum barrier including a one-dimensional image potential and an effective electron energy distribution. We simulate the energy-, distance- and bias-voltage-dependent transmission probabilities. In combination with a series of fermionic distributions of different amplitudes, temperatures and energy intervals, we model the measured I(z) curves. This approach allows us to quantify the contributions of hot electrons as well as multi-photon excited electrons to the tunneling current. We provide a comprehensive picture including voltage- and laser-power-dependent data.

This project is financially supported by the DFG in the SFB 1073 (project C4).

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