Berlin 2024 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 68: Poster: Scanning Probe Techniques: Method Development

O 68.3: Poster

Mittwoch, 20. März 2024, 18:00–20:00, Poster C

On the origin and elimination of cross coupling between tunneling current and excitation in scanning probe experiments that utilize the qPlus sensor — Michael Schelchshorn, •Fabian Stilp, Marco Weiss, and Franz J. Giessibl — University of Regensburg, Institute of Experimental and Applied Physics, Universitätsstrasse 31, D-93040 Regensburg, Germany

The qPlus sensor allows for the simultaneous operation of scanning tunneling microscopy (STM) and atomic force microscopy (AFM). When operating a combined qPlus sensor STM/AFM at large tunneling currents, a hitherto unexplained tunneling current-induced cross coupling can occur, which has already been observed decades ago. Here, we study this phenomenon both theoretically and experimentally; its origin is voltage drops on the order of μV that lead to an excitation or a damping of the oscillation, depending on the sign of the current. Ideally, the voltage drops would be phase-shifted by π/2 with respect to a proper phase angle for driving and would, thus, not be a problem. However, intrinsic RC components in the current wiring lead to a phase shift that does enable drive or damping. Our theoretical model fully describes the experimental findings, and we also propose a way to prevent current-induced excitation or damping.