LOCAL TRANSPORT-PROPERTIES OF THIN BISMUTH-FILMS STUDIED BY SCANNING TUNNELING POTENTIOMETRY

Charge transport in 20-30-Angstrom-thick Bi films is studied by scanni ng tunneling potentiometry at room temperature. Deposition at T=140 K onto InP-based multilayer substrates leads to flat and continuous film s that are subjected to a lateral current density of up to 8 X 10(6) A /cm(2). We find that scattering at surface defects and grain boundarie s gives rise to discontinuities in the local electrochemical potential . In particular, we observe dipole-shaped potential variations near sm all holes in the film. The influence of diffusive and ballistic transp ort on the formation of these dipoles is discussed.