Microstructures and properties of Er-doped Al2O3 thin films synthesized by ion beam assisted deposition

Er-doped Al2O3 thin films on the substrates of silicon and glass have been deposited by ion beam assisted deposition (IBAD) at different substrate temperature. We have studied the microstructures of the films and their annealing behavior by using transmission electron microscopy (TEM) and glancing-angle X-ray diffraction (GXRD). According to the results of TEM and GXRD, the films are dominantly amorphous when deposited below 500 °C. The films became polycrystalline γ-Al2O3 after annealing at 800 and 1000 °C for 6 h and unique α-Al2O3 after annealing at 1200 °C for 2 h. The hardness of the films increases with the increase of substrate temperature in the range of 70–500 °C and the adhesion between films to substrates decreases rapidly with the increase of substrate temperature when the substrate temperature is higher than 140 °C. The refractive index of films is in the range of 1.65–1.70 and high substrate temperature can improve the distribution of refractive index and optical loss of the films.