Effects of H2O on structure of acid-catalysed SiO2 sol-gel films

Abstract

Abstract Thin silica films were deposited on silicon wafers by the sol-gel technique, using spin coating. The sols were prepared by HCl catalysis of tetraethylorthosilicate (TEOS) diluted in ethanol, using different molar ratios, R, of H2O:TEOS. The films were then baked at various temperatures, and characterised using ellipsometry, profilometry, optical scattering and infrared spectroscopy. It was found that the thickness, shrinkage, porosity and pore sizes all decrease with increasing R. It was also found that high water levels yield films of higher homogeneity and finer texture, and less tensile stress.