Optical properties of cubic and monoclinic Y2O3 films prepared through radio frequency magnetron sputtering

Y2O3 films with different microstructures were deposited through radio frequency magnetron sputtering. The optical properties and the antireflection effects of the cubic and the monoclinic Y2O3 films on diamond substrates were investigated. Results showed that the cubic Y2O3 film had denser and more uniform grains with larger grain size. The band gap energies of the cubic and the monoclinic Y2O3 films were 5.79 and 5.88 eV, respectively. This finding was mainly attributed to the decrease in grain size from 30.1 nm to 20.6 nm. Meanwhile, the reflective indices of the cubic and the monoclinic films were 1.887 and 1.817, respectively. Furthermore, the monoclinic and the cubic Y2O3 films that have the same thickness generated antireflection effects on diamond at the 8-12 μm long-wave infrared (LWIR) range. However, due to the lower reflective index of the monoclinic Y2O3 film compared with that of the cubic Y2O3 film, the maximum antireflection effects of the Y2O3 films on diamond shifted to lower wavelengths.