Spectroscopic ellipsometry investigations of porous SiO ₂ films prepared by glancing angle deposition

We present the optical and the structural properties of porous SiO₂ films fabricated by using a glancing angle deposition technique. The influence of the glancing angle on the pseudorefractive index of porous SiO₂ films was studied by spectroscopic ellipsometry in the UV–visible region. The relationships among the pseudorefractive index, the porosity, and the glancing angle are determined. The results show that the pseudorefractive index decreases and the porosity increases with the increase of glancing angle. The minimum pseudorefractive index is found to be 1.11 at 532 nm for the porous SiO₂ film deposited at a glancing angle of 87°. The structural and surface morphology of these samples was also investigated by using a scanning electron microscope. The results indicate that the as‐deposited SiO₂ thin films are porous with a tilted‐columnar structure and low pseudorefractive index. Copyright © 2013 John Wiley & Sons, Ltd.