Coating of transparent water-repellent thin films by plasma-enhanced CVD

Abstract

Transparent water-repellent thin films are prepared by rf and microwave plasma-enhanced CVD (PECVD) methods using organosilicon compounds and fluoro-alkyl silanes (FASs) as source gases. First we prepare the water-repellent films by using three kinds of FASs by rf PECVD. The obtained contact angles depend on the length of perfluoro-alkyl groups (-C n F 2 n + 1 − , n = 1, 6 and 8) in FASs. The maximum contact angle is about 108° which is comparable to that for polytetrafluoroetylene (PTFE). Next we prepare the water-repellent films by mixing FAS and trimethylmetoxysilane (TMMOS) using microwave PECVD. The films consist of silicon oxide containing CF and SiCH 3 bonds and has high water repellency. The fluorine concentration at the surface does not relate directly to the contact angle. The films prepared by both PECVD methods are transparent in the visible region. PECVD is a suitable technique to prepare transparent water-repellent thin films at low substrate temperatures (below 100°C.