Preparation of Thin Composite Coatings by Sol-Gel Techniques

The formation and characterization of thin ceramic coatings is currently an active area in materials science. Specifically, there has been increased interest in these materials as dielectric and optical layers for advanced microelectronic circuitry [1]. This is in addition to their continued use and evaluation as protective coatings in a variety of applications [2]. One method of forming these coatings is via the sol-gel technique. However, only a few papers have been published in this area [3–7]. Dense silicon dioxide, aluminium oxide and various glass compositions have been deposited in thin film form on various substrates. Further, silicon dioxide films, formed by the sol-gel method, have been nitrided in ammonia at high temperatures and partially converted to an oxynitride [8–11]. These films were shown to be highly non-homogeneous, with a predominance of nitrogen at the surface. Despite the desirability of dense uniform well bonded coatings of the nitrided ceramics, i.e. Si3N4 and the oxynitrides, no method yet exists for the formation of nitrides by the sol-gel method.