Overview of optical properties of Al2O3 films prepared by various techniques

► Optical properties of Al2O3 films significantly depend on the preparation technique. ► Furthermore, for a given technique they depend on preparation conditions. ► We present optical properties of 13 Al2O3 samples prepared by 5 different techniques. ► We show how to prepare amorphous or γ-Al2O3 with n550 in the range of 1.46-1.69.