Structure and physical properties of W-doped HfO2 thin films deposited by simultaneous RF and DC magnetron sputtering

The W-doped HfO2 (HfO2:W) films were prepared by simultaneous RF magnetron sputtering of HfO2 and DC magnetron sputtering of W. The advantage of this method is that the W content could be independently controlled. The coexistence of W compounds and HfO2 was observed by XPS. Increasing the ratio of O2 to Ar pressure made the HfO2:W film be more stoichiometric. A control of the presence of HfWO5 is a way to enhance strongly the hydrophilicity of HfO2:W film. By decreasing the W content or increasing the ratio of O2 to Ar pressure, HfO2:W film exhibited lower surface roughness, higher visible transmission, a higher linear refractive index and a lower stress-optical coefficient.