THE ELECTRIC-FIELD UNDER A STM TIP APEX - IMPLICATIONS FOR ADSORBATE MANIPULATION

For a given bias voltage, a self-consistent calculation of the electrostatic polarization of the STM tip apex at tunneling distance to a conducting surface is presented. An effective atomic structure of the tip apex during a scan is constructed by fitting calculated and experimental STM scans on the Au(110) surface. The local electric field in the tip-sample gap is calculated. This leads to the inductive electrostatic potential energy gained by a physisorbed atom like xenon when the STM tip apex is approaching this adsorbate. Field induced diffusion processes of this adsorbate are discussed.