Optical properties of Fe2O3 deposited by IBAD and its usage in interference filters

This paper deals with thin films of Hematite (Fe2O3) deposited by ion beam assisted deposition (IBAD). It describes variation of optical properties with deposition parameters, especially oxygen flow and deposition rate. Optimal deposition parameters for Fe2O3 thin film were identified with criterion of the highest possible refractive index and lowest absorption. Film properties were measured and modelled by spectroscopic ellipsometry. Design of Fabry-Perot interference filter was used as a case study to compare properties of a Fe2O3 and TiO2 as a high refractive index materials. The first design uses combination of TiO2 and SiO2 layers, which is considered as a standard solution. The second design consists of Fe2O3 and YF3 layers. Comparison of these two designs shows that the design with SiO2 and Fe2O3 has considerably lower layer count. Due to the fact that Fe2O3 has significant absorption in the visible spectra its use is limited to red and infrared wavelengths. The paper describes deposition of designed filter (Fe2O3 and YF3) and measurement of its properties. Measured data are compared with the design.