Deposition process and property of silica films containing organic groups from aqueous solution of alkoxides

Silica thin films containing organic groups were directly deposited from aqueous solutions of silicon alkoxides. Effects of functional groups of the alkoxides and the deposition conditions on the preparation of the films were investigated in order to clarify the deposition process. Silica films containing methyl and phenyl groups were deposited from aqueous solutions of methyl- and phenyltrialkoxysilanes, respectively, in the pH region lower than 3 or higher than 6. The composition and the property of the deposited films were influenced by pH and the temperature of the solutions and the starting materials. The adhesion of the deposited films on hydrophobic substrates was lower than that on hydrophilic ones, although the films were formed on both surfaces. The refractive index of the methyl-containing films, ca. 1.44, decreased with removal of methyl groups by heating up to 500 °C.