Morphological, chemical and electrical characterization of thin film grown on rough and mechanically polished substrates

Abstract

Surface chemical composition and topography of thin films grown by radiofrequency (rf) reactive sputtering on two different substrates (rough and mechanically polished) were investigated by x-ray photoemission spectromicroscopy (XPSM) and atomic force microscopy (AFM). XPSM measurements showed, for both substrates, a homogeneous chemical composition of the films. The only difference was the observation of different charging in different areas of the film grown on rough alumina substrates, due, presumably, to a non-continuous film. AFM showed large topographical variations (several hundred nanometres) for the film grown on a rough alumina substrate, due to structures already present on the substrate. The estimated roughness of the sensor was 20% larger for the film grown on a rough alumina substrate. The response to carbon monoxide was 30% higher for the sensor grown on rough alumina than that on polished alumina, reflecting the larger exposed sensor area.