Abstract

Optically transparent films of MgO, Al₂O₃, ZnS, and TiO₂ of thicknesses in the 130–200-nm range on ~1-cm thick vitreous silica substrates were examined by spectroscopic ellipsometry (SE) in the 280–800-nm wavelength range. These data were then analyzed by the linear regression analysis technique using appropriate models to yield the model parameters within 90% confidence limits. MgO films were found to be free of low density regions or voids, unlike Al₂O₃ films which had an effective void fraction f_v of 15 ± 0.4% and the TiO₂ film for which f_v was found to be 18 ± 1%. In the case of ZnS films the observed SE data could be explained satisfactorily only with a three-layer model with the following model parameters: (i) 11.6 ± 0.5-nm thick layer adjacent to the substrate with a void fraction f_v of 3 ± 1%, (ii) an intermediate layer of 4.8 ± 0.8 nm thick with f_v of 1 ± 1%, and (iii) the outermost layer 21 ± 0.3 nm thick with an effective void fraction f_v of 17 ± 2% representing the microrough surface layer of the film.

© 1986 Optical Society of America