VARIATION OF THE THERMOVOLTAGE ACROSS A VACUUM TUNNELING BARRIER - COPPER ISLANDS ON AG(111)

If there is a temperature difference between tip and sample of a scann ing tunneling microscope a thermovoltage is generated which is very se nsitive to the electronic states involved in the tunneling process. Th is has been used, e.g., to distinguish between different metals of a h eterogeneous metallic surface. To demonstrate the capability of this m ethod it has been applied to copper islands on a Ag(lll) surface. Know ing the thermopower for chemically homogeneous silver and copper surfa ces of -45 and -15 mu V/K, respectively, islands of copper on the silv er substrate can be well identified with a lateral resolution of 1 nm. (C) 1995 American Institute of Physics.