Formation of Porous Silicon Oxides for Single-Layer Anti-reflection Coatings on Transparent Materials Using Atmospheric-Pressure Very High-Frequency Plasma

We study a formation process of single-layer anti-reflection coatings using porous silicon oxide (SiOx) films formed in atmospheric-pressure (AP), very high-frequency (VHF) plasma. A two-step process is proposed for forming porous SiOx films: deposition of carbon and hydrogen-containing silicon oxide (SiOCH) layers on a substrate on which polystyrene nanospheres are pre-arranged in hexamethyldisiloxane and hydrogen-fed AP-VHF plasma and subsequent removal of the polystyrene nanospheres/transformation of the SiOCH layer into inorganic SiOx one by post-oxidation in oxygen-fed AP-VHF plasma. Transmission electron microscopy and energy dispersive X-ray analyses have confirmed that the polystyrene nanospheres underlying the SiOCH layer are effectively removed by the post-oxidation and that air is introduced into the place where the polystyrene nanospheres are present, which are supported by the optical reflectance measurements. The reaction mechanism during the post-oxidation process is discussed, based on the Fourier transform infrared adsorption spectroscopy measurements.