STM OF MANIPULATED STRUCTURES - CHARACTERIZATION OF METAL-OXIDE FILMS

An overview is given on the use of scanning tunneling microscopy for characterizing metal oxide layers. We describe results on the initial stages of oxidation of Ni(100), on the preparation and measurement of a thin ordered layer of Al2O3 grown on NiAl(110), and on experiments to grow ordered NiO on Au(111) by evaporation of Ni in an O-2 atmosphere. It is demonstrated that at low sample-bias voltages tunneling is accomplished by the substrate electrons while for higher voltages the electronic states of the oxide film contribute to tunneling. This phenomenon can be used as a fingerprint for the identification of oxide species. Finally, we show characteristic results for a condensed metal (Ag) on an oxidized and on a metal surface.