DIPOLE TIP MODEL INVESTIGATION OF RESONANCE EFFECTS IN SCANNING-TUNNELING-MICROSCOPY

The distribution of the tunneling current in the semiclassical mode of operation of the scanning tunneling microscope is studied using an ax ially symmetric 3-D tip. The tip is taken as an equipotential of a dip ole, thus giving an analytical form for the potential and the field li nes between the tip and the surface, with the latter taken to be atomi cally flat and corresponding to the zero equipotential plane. Field em ission resonance calculations are made, allowing conductance and tip-t o-surface separation to be determined as functions of bias voltage at constant current. Results are compared with the measurements of Becker , Golovchenko, and Swartzentruber [Phys. Rev. Lett. 55, 987 (1985)]. ( C) 1996 American Institute of Physics.