Microstructural characterization of sol-gel derived PbTiO₃ thin films

Abstract

A process has been developed for the fabrication of continuous, crack-free layers, of a series of compositions in the PbO-La 2 O 3 -TiO 2 -ZrO 2 system. These layers were formed by spin-casting solutions of complex alkoxides onto platinum, silicon, silica, and a variety of substrates. The dried layers were amorphous gels which could be densified and converted to ceramic films at relatively low temperatures (e.g., 350-500°C). Gellation was caused by the condensation polymerization of alkoxide molecules, and was initiated by hydrolysis of the alkoxy groups. Gel structures were manipulated by controlling hydrolysis conditions (catalyst and amount of water) in an effort to control pyrolysis behaviour, optimize microstructures, and minimize firing temperatures. Lower processing temperatures increased the compatibility with substrates such as Si wafers. Structural control was possible because the polymerization reactions become site-specific under certain hydrolysis conditions. As discussed below, microstructures of thin films were influenced considerably by both the type of catalyst, and by interactions with silicon substrates.