On refractive index of optical radiation of polycrystalline silicon films

Transmission spectra of layers of polycrystalline silicon on sapphire with a thickness of 0.1 … 0.8 µm were investigated. The refractive indices were determined in the range of 0.5 … 2.7 μm. An increase in the refractive index with decreasing wavelength was established. An increase in the film thickness from 0.1 to 0.8 μm led to a decrease in the refractive index from 3.2 to 2.8 at λ = 1.5 μm. Compared to single crystals, the refractive indices of polycrystalline films were lower. The data obtained can be used to build models for calculating the optical characteristics of complex compositions.