ATOMIC-FORCE MICROSCOPY CHARACTERIZATION OF SPUTTERED VANADIUM-OXIDE THIN-FILMS GROWN ON AL2O3 SUBSTRATE

Vanadium oxide (V2O5) thin films, which are good candidates for the re alization of gas detectors, have been grown on rough alumina substrate s and characterized by atomic force microscopy (AFM). The films were p repared by radiofrequency reactive sputtering, with different concentr ations of oxygen in the growth atmosphere; after deposition the sample s were thermally treated in order to get the best sensitivity to diffe rent gases. Because of the structures already present on the rough alu mina substrate, AFM showed large topographical variations (several hun dred nanometers) for V2O5 films grown on a rough alumina substrate. Fo r both thermally treated and untreated samples, the roughness increase s with increasing percentage of oxygen, but the sample with the best s ensing properties (15% of oxygen) shows a characteristic minimum. More over, we observe that the thermal treatment also produces a general de crease in roughness, which is especially marked in samples with a low percentage of oxygen. The sensor has been tested with NO2, and the bes t sensitivity was obtained for an operating temperature around 300 deg rees C.