Syntheses and optical properties of low-temperature SiOx and TiOx thin films prepared by plasma enhanced CVD

Abstract

SiOx, TiOx and SiOx–TiOx mixed thin films were prepared by PECVD at a substrate temperature below 80°C using tetraethoxysilane (TEOS) and ethyltrimethylsilane (ETMS) for SiOx and titaniumtetraisopropoxide (TTIP) for TiOx, respectively. Optimal deposition conditions for preparing SiOH free ETMS SiOx are control of the external magnetic field and use of Ar as a excitation gas. The refractive index of SiOx increased with the ratio of infrared absorption intensity of Si–C to that of Si–O, which is related to the stoichiometry of SiOx determined by Si–O–Si stretching absorption frequency and XPS analysis. The refractive index ( n) of SiOx varied from 1.459–1.559 with extinction coefficient ( k) lower than 3.0×10 −4. This index of TiOx was from 1.750–2.047 and k lower than 2.0×10 −3. The refractive index of mixed SiOx–TiOx thin film can be varied from 1.460–1.820 by controlling fraction constituents content.