How to select fast scanning frequencies for high-resolution fast STM measurements with a conventional microscope

The implementation of fast measurement modes in conventional scanning tunneling microscopes (STM) generally implies that at least the fast scanning frequency reaches or exceeds the first resonance frequency of the scanning stage. We present a straightforward protocol for the determination of accessible frequency windows, where high spatial resolution can be routinely achieved and maintained during the fast scanning movement. This protocol relies on a simple, in situ method to locate these frequency windows by measuring the response in the characteristic probe signal while varying the tip-sample distance. The method is compared to other approaches used to characterize the resonant behavior of STMs. In principle, the protocol can also be applied to other types of scanning probe microscopes with sufficiently fast probe signal detection, as a general approach to upgrade these instruments to faster imaging rates.