Optical characterization of silicon dioxide thin films prepared by ion-assisted electron beam deposition

A single-layer SiO2 film is deposited using ion-assisted electron beam evaporation technique, and the deposited film is characterized using variable angle spectroscopic ellipsometry, UV–Vis–NIR spectrophotometer, coherence correlation interferometer, and Abbe refractometer as well as image processing techniques to investigate its optical and surface properties. The surface quality of the film in terms of average roughness, kurtosis, skewness, and power spectral density (PSD) is analyzed using interferometer and image processing. The refractive index of the SiO2 film is found to increase from 1.452 to 1.482 at 550 nm with increase in film thickness. This is corroborated by Abbe refractometer findings where the film refractive index is found to be 1.46490 and 1.48226 for a film thickness of 100 and 400 nm, respectively. The SiO2 film also results in reduction in average surface roughness from 35 nm of the uncoated substrate to 0.15 nm of the coated surface. Statistical indicators of surface quality extract from interferometric images such as kurtosis, skewness, and PSD and also exhibit sharp decline in their respective values of the coated surface as compared to the uncoated substrate indicating improvement in the surface quality after coating.