溶胶凝胶中独立的厚膜讲解.doc

Self-Standing Thick Films INTRODUCTION One of the most important technological aspects of sol–gel processing is the preparation of thin films by common techniques such as dip- or spin-coating. A wide variety of materials with special functions of optical and opto-electronic importance have been produced to date by the application of these coating methods. However, the dip- and spin-coating methods include the experimental experience that inorganic films thicker than 1 μm are virtually impossible to dry without cracks regardless of the drying rate (Brinker and Scherer, 1990). On the other hand, there are various economical demands for oxide films with a thickness of the order of several micrometers formed on substrate materials in the field of electrical, optical and opto-electronic devices (Kawachi, 1990; Moilanen, 1994). The formation of such oxide films have been made by repetitive spin-coating and rapid thermal annealing (Syms and Holmes, 1994), flame hydrolysis (Kawachi, 1983), plasma CVD (Grand, 1990), screen printing (Fernandes, 1995; Futakuchi, 1999; Akiyama, 1999), hydrothermal process (Shimomura, 1991), gas deposition process (Ichiki, 1997), electrophoresis (Nishimori, 1995), etc. But each process has drawback inherent to the method. Some of them are time-consuming and less economical. Others require high sintering temperature and sometimes give the films of low density or poor flatness. Recently a new technique of forming oxide gel films corresponding to oxide films of several to 20 μm in thickness based on interfacial polymerization was developed by a research group of Tokyo Institute of Technology (Yamane, 1994). The technique originally developed aiming the formation of a thick silica glass film on a silicon substrate for the purpose of the fabrication of a planer wave guide enlarged the restricted film thickness related to conventional sol–gel processing and was extended to the formation of thick PZT films used for piezoelectric devices in MEMS such as