Optical properties of hafnia and coevaporated hafnia:magnesium fluoride thin films

Mixed films of HfO(2) and MgF(2) were prepared by the e-beam coevaporation of two source materials with or without the presence of ion assistance. Optical properties and hardness of mixed films were compared among various compositions that were achieved by controlling the deposition rate of MgF(2). Results obtained from pure materials confirmed the densification of HfO(2) and the increased absorption in MgF(2) with a higher discharge voltage. A refractive index of a composite film from 1.38 to 1.91 was achievable with various HfO(2):MgF(2) deposition rate ratios. A low-index composite material with improved hardness may be substituted for the soft MgF(2).