MORPHOLOGICAL, CHEMICAL AND ELECTRICAL CHARACTERIZATION OF PT-SNO2 THIN-FILM GROWN ON ROUGH AND MECHANICALLY POLISHED AL2O3 SUBSTRATES

Surface chemical composition and topography of Pt-SnO2 thin films grow n by radiofrequency (rf) reactive sputtering on two different Al2O3 su bstrates (rough and mechanically polished) were investigated by x-ray photoemission spectromicroscopy (XPSM) and atomic force microscopy (AF M). XPSM measurements showed, for both substrates, a homogeneous chemi cal composition of the Pt-SnO2 films. The only difference was the obse rvation of different charging in different areas of the film grown on rough alumina substrates, due, presumably, to a non-continuous Pt-SnO2 film. AFM showed large topographical variations (several hundred nano metres) for the Pt-SnO2 film grown on a rough alumina substrate, due t o structures already present on the substrate. The estimated roughness of the sensor was 20% larger for the Pt-SnO2 film grown on a rough al umina substrate. The response to carbon monoxide was 30% higher for th e sensor grown on rough alumina than that on polished alumina, reflect ing the larger exposed sensor area.