Atomic force microscope studies of ultra thin silica film formation from adsolubilized tetra-N-butoxysilane polymerization on mica

Abstract

Admicellar polymerization is a proven method of assembling ultr thin films, which play important roles in functionally specific surface catings, catalysis, and semiconductors. However, only the formation of organic polymers throught this technique has been examined to date. In this study we utilized atomic force microsocopy to examine the admicellar polymerization of tetra-nbutoxysilane (TBOS) adsolubilization in the cetyltrimetylammonium bromide (C16TAB) admicelles to form ultra thin silica films on freshly cleaved mica surfaces in aqueous solution. The TBOS reaction on mica was examined both with and without the presence of C16TAB and in both queous conditions and in air. System variables included TBOS feed concentration and reaction time. It was found that TBOS concentration strongly affected the structure of the formed surface aggregate on mica in TBOS-C16TAB solution. Fibrous, spherical, and flat sheet-like sheet-like aggregats were observed as the TBOS concentration was increased. The structure of surface aggregates directly affected the structure of the dried silica film. Reaction times of twenty-four hours of loger were needed to obtain a stable silica film.