Abstract: Preparation of hydrophobic SiO2 thin film is reported.The solution is prepared by a acid/base 2-step method and then modified by TMCS (trimethylchlorosilane).Ellipsometry,FTIR,SEM,and contact angle instrument were used to measure the physical properties of the thin films.The results show that the refractive index of thin film is controlled between 1.33 and 1.18,OH groups on the surface of SiO2 particles have been partly replaced by CH3 groups,the contact angle is increased to 120 degree of modified films from 40 degree of unmodified films.

Key words: Sol-gel process, Silica, Surface modification, Hydrophobic films