Characterization of hafnia thin films made with different deposition technologies

Abstract

In this study, single layer hafnium dioxide thin films were prepared by electron beam deposition (EBD), ion assisted deposition (IAD) with End-Hall and APS ion sources, and ion beam sputtering (IBS). The starting materials for EBD and IAD were hafnium and granulated hafnia, whereas the target for IBS was hafnium. Comprehensive characterization of these films such as structural and optical properties, surface topography and weak absorption have been studied via Xray diffraction (XRD), Lambda 900 spectrophotometer, variable angle spectroscopic ellipsometry (VASE), scanning electron microscopy (SEM), ZYGO interferometer, and Laser Calorimeter. The results show that thin film properties have a close relationship with deposition technologies. The EBD and IBS films are largely amorphous, however, the IAD films with different ion sources are all polycrystalline but with different crystal structures. Comparison with EBD films, the IAD and IBS films, of which the structures are very compact, represent higher refractive index and weak absorption. RMS roughness and total integrated scattering (TIS) of IAD and IBS films were lower than the EBD films. All of these results are useful to investigate the laser-induced damage threshold (LIDT) of hafnium dioxide thin films and hafnia/silica high reflectors for high power laser applications.