Properties of silica and silica-titania layers fabricated from silica sols containing fumed silica

The appearance and thickness of prepared single silica and silica-titania layers have been characterized by optical microscopy and scanning electron microscopy. Optical properties of layers have been determined by spectral ellipsometry and UV-VIS-NIR transmission spectrometry. The measurements have shown that characteristics of layers fabricated from both types of the sols differ and that one can obtain stable transparent silica layers with thicknesses up to 650 nm and refractive indices in a range from 1.41 to 1.44 at 600 nm using TEOS sols containing fumed silica. It has been found that larger layer thicknesses can be achieved by using silica sols with fumed silica, by increasing the alkoxide concentration, by using increased withdrawing velocities, and by decreasing heat-treatment temperatures.