Noise in vacuum tunneling: Application for a novel scanning microscope

Abstract

The noise in the tunneling current of a scanning tunneling microscope (STM) has been investigated. At gap voltages above a few mV the current noise shows a 1/f spectral distribution over a range of 1 Hz to 100 kHz. However, at zero bias white noise scaling like thermal noise for the equivalent gap resistance is found. Due to its exponential distance dependence, this noise at zero bias can be used to adjust the tip-to-sample distance with an accuracy similar to the conventional STM method. The performance of a scanning microscope based on this principle is demonstrated.