NCAFM2023 Programme Booklet

ON THE ORIGIN AND ELIMINATION OF CROSS COUPLING BETWEEN EXCITATION AND TUNNELING CURRENT IN SCANNING PROBE EXPERIMENTS THAT UTILIZE THE qPlus SENSOR

Michael Schelchshorn, Fabian Stilp, Marco Weiss, Alfred J. Weymouth and Franz J. Giessibl

Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany Email: fabian.stilp@ur.de

The qPlus sensor allows simultaneous measurements of scanning tunneling microscopy (STM) and atomic force microscopy (AFM). Its design for use in frequency modulation AFM (FM-AFM) involves separate electrodes, applied on an oscillating quartz cantilever, for the detection of an electronic tunneling current and the deflection signal. Cable resistance and capacities in the electronic setup can induce cross talk phenomena. We report a tunneling current-induced cross coupling observed in a combined STM/AFM setup which uses the qPlus sensor. This cross coupling can induce a positive or negative change of the amplitude excitation signal, thus acting as an apparent dissipation or drive. The experimental data is explained well by tunneling current-induced fluctuations of the electric potential on the sensor electrodes.

Fig. A Relevant section of the microscope’s STM electronics. B Tunneling current during z-spectroscopy measurements. C Excitation signal ensuring a constant oscillation amplitude showing an apparent dissipation or drive of the sensor for positive or negative bias voltages.

References [1] M. Schelchshorn, F. Stilp, M. Weiss, F. J. Giessibl, arXiv:2303.16850, 2023

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