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O: Fachverband Oberflächenphysik

O 2: Scanning probe techniques: Method development I

O 2.1: Vortrag

Montag, 12. März 2018, 10:30–10:45, MA 004

Near-field driven nonlinear photoemission from the tunnel junction of a Scanning Tunneling Microscope — •Benjamin Schröder, Katharina Kaiser, Thomas Kotzott, Murat Sivis, Claus Ropers, and Martin Wenderoth — IV. Physikalisches Institut, Georg-August-Universität Göttingen, Germany

Scanning Tunnelling Microscopy (STM) is a vital tool for surface chemistry: It gives access to the molecular configuration and the highly site-specific dependencies of chemical reactions. Furthermore, it can drive chemical reactions of individual molecules by applying static fields or injecting electrons by the tunnel current. A desirable extension is the excitation by strongly localized light fields providing intensities that are suitable to trigger nonlinear optical processes.
Here, we present the combination of an ultra-high vacuum low-temperature STM with a femtosecond laser oscillator. The strongly confined optical near-field at the apex is generated by using plasmonic gold nanotips as tunnelling probes. As a demonstration of the field localization, we drive multiphoton photoemission from the tunnel junction under STM operation. The unique capability of the STM to control the tip-sample distance on a sub-Ångström scale allows for the disentanglement of tunnel- vs. photocurrent. We show that the photocurrent gives a topographic contrast of nanometer-scaled surface features.
This project is financially supported by the DFG in the SFB 1073 (project C4).