Optical properties of oxidized plasma-polymerized organosilicones and their correlation with mechanical and chemical parameters

Abstract

Pure tetravinylsilane and its oxygen mixture were used to deposit oxidized plasma polymer films at various effective power (0.1-10 W) and various oxygen fractions (0-0.71) using RF pulsed plasma. The optical properties (refractive index, extinction coefficient, band gap) of the deposited films were investigated by spectroscopic ellipsometry (230-830 nm) using an optical model and Tauc-Lorentz parametrization. Analyses of chemical and mechanical properties of films allowed for the interpretation of changes in optical properties with deposition conditions. The refractive index was revealed to increase with enhanced effective power due to the increased crosslinking of the plasma polymer network but decreased when increasing the oxygen fraction due to the decrease of polymer crosslinking as the number of carbon bonds in the plasma polymer network was eliminated. A very strong positive correlation was found between the Young's modulus and the refractive index for oxidized plasma polymer films. The optical properties of films correlated with their chemical properties for the specific deposition conditions used in this study. The band gap (1.9-2.9 eV) was assumed to be widened due to the increased concentration of vinyl groups in oxidized plasma polymer films.