XPS studies on the interaction of CeO2 with silicon in magnetron sputtered CeO2 thin films on Si and Si3N4 substrates

CeO2 thin films were deposited on silicon and silicon nitride substrates by magnetron sputtering at room temperature and annealed at 400 and 600 °C in air and vacuum. Interaction between deposited CeO2 and Si in CeO2/Si and CeO2/Si3N4 systems was investigated by XPS. The results show that Ce is present as both Ce4+ and Ce3+ oxidation states in CeO2 film deposited on Si substrate, whereas Ce4+ is the main species in as-deposited CeO2/Si3N4 film. Detailed analyses of Ce3d, Si2p and O1s core level spectra demonstrate that Ce2O3 and SiOx or cerium silicate type of species are formed at the interface of CeO2 and Si. Concentrations of Ce3+ species increase drastically in CeO2/Si thin films after annealing at 400 °C in vacuum due to enhanced interfacial reaction. On the other hand, interfacial reaction between CeO2 and Si3N4 substrate is limited in as-deposited as well as heat treated films.