Comparison of the optical properties and UV radiation resistance of HfO 2 single layers deposited by reactive evaporation, IAD, and PIAD

Abstract

HfO 2 is one of the most important high index thin film materials for the manufacture of interference coatings in the DUV spectral region down to 248 nm. High quality coatings and multilayer interference systems in conjunction with SiO 2 as low index material can be deposited by various PVD technologies including reactive e-beam evaporation (RE), ion assisted deposition (IAD) and plasma ion assisted deposition (PIAD). Thin HfO 2 films with optical thickness up to 3(lambda) /4 were deposited by RE, IAD and PIAD onto fused silica. The optical and structural properties of these films were investigated. The optical properties are related to the film structure and film density. The interaction of UV radiation with photon energies close to the band gap of HfO 2 with different films was studied. LIDT at 248 nm were determined in the 1- on-1 and the 1000-on-1 test mode in dependence on the deposition technology and the film thickness. LIDT values of all investigated films decrease with increasing thickness due to the higher absorption and defect density. Additionally, data on the radiation resistance of interference coatings containing HfO 2 will be presented.