Scattering phenomena in porous sol-gel-derived silica films

Abstract

This paper presents the results of investigations of optical scattering phenomena in porous silica films. SiO2 films were prepared by the sol-gel method and deposited on polished silicon wafers by the dip-coating technique. Fabricated films were studied using integrating sphere reflectometry, spectroscopic ellipsometry, atomic force microscopy, scanning electron microscopy, and angular resolve scattering. The spectral characteristics of the refractive and extinction indices and scattering extinction coefficients are presented. Additionally, the depolarization of reflected beam from samples was measured. The tested films were characterized by a thickness of 500 to 900 nm, a porosity of 50%, and refractive indices of less than 1.24. The observed depolarization of light reflected from SiO2 films resulted from surface and bulk scattering. This phenomenon resulted from the presence of surface and closed pores located in the bulk of SiO2 film.