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

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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.