Fast low-noise transimpedance amplifier for scanning tunneling microscopy and beyond

M. Štubian, J. Bobek, M. Setvin, U. Diebold, M. Schmid

Institut für Angewandte Physik, TU Wien, 1040 Wien, Austria
Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, 180 00 Prague 8, Czech Republic

Rev. Sci. Instrum. 91 (2020) 074701

A transimpedance amplifier has been designed for scanning tunneling microscopy (STM). The amplifier features low noise (limited by the Johnson noise of the 1 GΩ feedback resistor at low input current and low frequencies), sufficient bandwidth for most STM applications (50 kHz at 35 pF input capacitance), a large dynamic range (0.1 pA-50 nA without range switching), and a low input voltage offset. The amplifier is also suited for placing its first stage into the cryostat of a low-temperature STM, minimizing the input capacitance and reducing the Johnson noise of the feedback resistor. The amplifier may also find applications for specimen current imaging and electron-beam-induced current measurements in scanning electron microscopy and as a photodiode amplifier with a large dynamic range. This paper also discusses the sources of noise including the often neglected effect of non-balanced input impedance of operational amplifiers and describes how to accurately measure and adjust the frequency response of low-current transimpedance amplifiers.

Corresponding author: Michael Schmid (schmid at iap_tuwien_ac_at).

Users with online access to Review of Scientific Instruments can load the article from the publisher.