Properties of fluorinated silica glass deposited at low temperature by atmospheric plasma-enhanced chemical vapor deposition

The atmospheric pressure plasma-enhanced chemical vapor deposition of fluorinated silica glass was demonstrated at a temperature of 120 °C. The process was carried out by simultaneously feeding tetramethylcyclotetrasiloxane (TMCTS) and triethoxyfluorosilane (TEOFS) into the afterglow of helium and oxygen plasma. The effect of the flow rate of the fluorinated precursor on the growth rate, composition, and optical properties was examined. The ratio of atomic fluorine to atomic silicon increased up to 10% at a TEOFS/TMCTS atomic Si feed ratio of 1.3 and then leveled off. Coatings made from pure TMCTS and both precursors showed higher surface roughness and porosity, and more hydroxyl content compared to coatings made from pure TEOFS. The refractive indices at 633 nm of films produced using pure TMCTS, a TEOFS/TMCTS atomic Si feed ratio of 1.3 and pure TEOFS were 1.457, 1.449, and 1.411, respectively.