XPS ANALYSIS OF THE INTERFACE OF CERAMIC THIN-FILMS FOR HUMIDITY SENSORS

MgAl2O4 thin films, deposited on Si/SiO2 substrates, were studied as h umidity sensors. This paper discusses the evaluation of the chemical c omposition at increasing depths, carried out by a combination of Ar+ i on etching and XPS analysis. These analyses showed the simultaneous pr esence of Mg, Al and Si at the film/substrate interface. The thickness es of the interfaces were calculated between 7 and 10 nm. The shift in tl.e binding energies of the XPS peaks observed at the interface seem s to demonstrate the occurrence of a chemical interaction between film and substrate. At the interface, Si 2p binding energy values are char acteristic of a silicate, and this effect may be responsible for the g ood adhesive properties of MgAl2O4 filMs to silica, as demonstrated by peel tests with Scotch tape.