Cancelling Picometer Vibrations from a Scanning Tunneling Microscope by Post Processing

Scanning tunneling microscopy (STM), a crucial tool for atomic resolution measurements of the electronic structure of condensed matter systems, typically requires an extremely stable environment to operate. Modern ultra-low vibration laboratories are designed to reduce external vibrations from the micron scale to the nanometer scale, by employing large pneumatic isolators to float inertial blocks. Improvements beyond this benchmark require careful STM head design to minimize weight and reduce internal resonances. However, even the best microscopes experience picometer vibrations in the tip-sample junction. Here we introduce a software algorithm that can reduce residual picometer vibrations by more than 50%. Our method focusses on accurately measuring the transfer function for vibrations to reach the tip. By measuring vibrations with a sensitive geophone, the transfer function allows us to predict their induced noise at the tip. We apply this technique to topographic data acquired on a passively isolated STM, and are able to reduce the tip-sample rms displacement from 0.6 pm to 0.35 pm. We anticipate extending this method to reduce noise in spectroscopic measurements of the density of states.