Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 35: Poster Session I (Scanning probe methods)

O 35.14: Poster

Dienstag, 15. März 2011, 18:30–22:00, P3

A low-noise STM equipped with a cryogenic transimpedance amplifier — •Martin Kunz and Jörg Kröger — Institut für Physik, Technische Universität Ilmenau, 98693 Ilmenau, Germany

We present the current status of a home-built scanning tunnelling microscope (STM) designed to be operated inside a helium cryostat at 4.2 K in an ultrahigh vacuum. The influence of electromagnetic interference on the tunnelling signal, which is a serious noise source in tunnelling experiments, is minimized by placing a transimpedance amplifier in close vicinity to the tunnelling probe. This custom-built amplifier has a bandwidth from DC to 100 kHz. It is thermally coupled to the cryostat and can be deployed at temperatures ranging from liquid helium to room temperature. In particular, at low temperatures the signal degradation due to Johnson noise is significantly smaller than in conventional STM setups that employ transimpedance amplifiers operated at room temperature. The microscope is primarily intended for spin-resolved spectroscopic investigations of electronic and vibrational excitations.