HfO2 single layers and HfO2/SiO2 high reflectors with standard 1/4 wavelength design were prepared by ion assisted deposition (IAD) with APS ion source and ion beam sputtering (IBS). Characterization of HfO2 single layers such as structural and optical properties, surface topography and absorption have been studied. The laser-induced damage thresholds (LIDTs) of the high reflectors with different multilayer stacks at 1064nm were tested with S-on-1 testing mode according to ISO-11254. In addition, optical properties, surface topography and absorption of these testing high reflectors have also been investigated in our experiments. All the results used to analyze the LIDTs of high reflectors have been discussed and interpreted in literature.
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.