Characterisation of sol-gel-derived silica films

Sol-gel-derived silica films were fabricated by dip-coating onto silicon and glass substrates. Film properties such as thickness and temporal stability were monitored as a function of dip speed, water:precursor ratio, sol aging time and time after dipping. Film behaviour was interpreted in terms of the dependence of hydrolysis and condensation rates on the interplay between sol pH and water:precursor ratio. Film thickness was found to increase by approximately a factor of two as water:precursor ratio increased from two to six. Film thickness also increased with sol pre-polymerisation time. The time to achieve film stability was decreased at higher water:precursor ratios. Surface quality was correlated with processing conditions.