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 of SiO2. The oxidation state of tin under different experimental conditions of preparation has been characterized by XPS and ELS and a procedure has been found to produce pure SnO. For comparison, SnO has been evaporated on highly oriented pyrolytic graphite (HOPG). In this case, independent of the deposited amount of SnO, XPS and ELS did not show any significant difference in the photoemission and loss features of this 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 showed a shift of similar to 1 eV in the BE of then 3d(5/2) peak and another of similar to 1.7 eV in the values of the Auger parameter with respect to the values found for the bulk material. These shifts, very common on deposited metal particles, have been previously reported by us for TiO2/SiO2, and are tentatively attributed to the effect of the interaction of small deposits of SnO with the surface of SiO2. The characterization by ELS and valence band photoemission of SnO completes the set of results reported in this paper.