SCANNING TUNNELING MICROSCOPY SPECTROSCOPY INVESTIGATIONS OF THE INTERFERENCE EFFECTS CAUSED BY THE CIRCULAR PITS ON THE THERMALLY OXIDIZEDGRAPHITE SURFACE/

The thermal oxidation of the graphite leads to the removal of monoatom ic carbon layers from the surface and formation of circular pits on th e exposed plane. Near the pit edges the scanning tunneling spectroscop y measurements show a series of very narrow flat regions on the I/V ch aracteristics. The observed I/V flat regions appear only when the char acteristic is recorded very close to the pit edges. The appearance of tunneling current steps can be explained by the oscillating character of the local density of states near the pit edges. A simple quantum me chanical model in 2D based on boundary condition for an electron wave function is proposed.