Comparison of the optical properties and UV radiation resistance of HfO2 single layers deposited by reactive evaporation, IAD, and PIAD

HfO2 is one of the most important high index thin film materials for the manufacture of interference coatings in the DUV spectral region down to 248nm. High quality coatings and multilayer interference systems in conjunction with SiO2 as low index material can be deposited by various PVD technologies including reactive e-beam evaporation (RE), ion assisted deposition (LAD) and plasma ion assisted deposition (PIAD). Thin HfO2 films with optical thickness up to 3l/4 (l=248mn) 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 HfO2 with different films was studied. LIDT at 248nm 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 invest igated films decrease with increasing thickness due to the higher absorption and defect density. Additionally, data on the radiation resistance of interference coatings containing HfO2 will be presented.