INTERFACE EFFECTS FOR METAL-OXIDE THIN-FILMS DEPOSITED ON ANOTHER METAL-OXIDE .1. SNO DEPOSITED ON SIO2

The growing mode of SnO overlayers deposited on SiO2 has been studied by ISS and XPS. This study has shown that SnO spreads on the surface o f SiO2. The oxidation state of tin under different experimental condit ions of preparation has been characterized by XPS and ELS and a proced ure has been found to produce pure SnO. For comparison, SnO has been e vaporated on highly oriented pyrolytic graphite (HOPG). In this case, independent of the deposited amount of SnO, XPS and ELS did not show a ny significant difference in the photoemission and loss features of th is material as a function of coverage (i.e. there are no size effects) . On the contrary, at low coverages of SnO deposited on SiO2 XPS showe d a shift of similar to 1 eV in the BE of then 3d(5/2) peak and anothe r of similar to 1.7 eV in the values of the Auger parameter with respe ct to the values found for the bulk material. These shifts, very commo n on deposited metal particles, have been previously reported by us fo r TiO2/SiO2, and are tentatively attributed to the effect of the inter action of small deposits of SnO with the surface of SiO2. The characte rization by ELS and valence band photoemission of SnO completes the se t of results reported in this paper.