Photoluminescent properties of undoped and Ce-doped HfO2 thin films prepared by magnetron sputtering

The undoped and Ce-doped HfO2 thin films synthesized by magnetron sputtering on silicon substrates were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL). XRD measurements of these films showed that the crystalline structure depends on the doping concentration. The samples underwent a crystallographic change from monoclinic to cubic phase with increasing doping concentration. A violet PL band associated with oxygen vacancies was observed in undoped HfO2 at room temperature. While a blue PL band appeared after introducing cerium ion into the HfO2 host, which is ascribed to the well-known 5d-4f emission band of the cerium ion.