Conductance oscillations in scanning tunneling microscopy as a probe of the surface potential

A free-electron model of the device is used to study oscillations in the differential conductance as a function of applied voltage, observed when the microscope is operated in constant current mode. These oscillations are found to be sensitive to the shape of the potential at the sample surface, giving a new method to study surfaces with the tunneling microscope. The rapid damping of the oscillations seen experimentally is suggested to result, from roughness of the probe tip.