Evaluation of an Electric Field over Sample Surfaces by Electron Standing Waves in a Vacuum Gap of Scanning Tunneling Microscopy

Electric field intensities over sample surfaces have been evaluated from peak intervals of differential conductance oscillation due to electron standing waves, which are excited in a vacuum gap of scanning tunneling microscopy. By comparing the intervals measured for different samples of Au(111), Si(111), Si(001) and Ge(001) with tips of similar radius, we have demonstrated that the electric field intensities are different on these surfaces. This study provides a new method to evaluate the electric field near surface regions on a nanometer scale.