title: Room-temperature formation of low refractive index silicon oxide films using atmospheric-pressure plasma.
abstract: This study aims to apply atmospheric-pressure (AP) plasma to the fabrication of single-layer anti-reflection (AR) coatings with porous silicon oxide. 150 MHz very high-frequency (VHF) excitation of AP plasma permits to enhance the chemical reactions both in the gas phase and on the film-growing surface, increasing deposition rate significantly. Silicon oxide films were prepared from silane (SiH4) and carbon dioxide (CO2) dual sources diluted with helium. The microstructure and refractive index of the films were studied using infrared absorption and ellipsometry as a function of VHF power density. It was shown that significant increase in deposition rate at room temperature prevented the formation of a dense SiO2 network, decreasing refractive index of the resulting film effectively. As a result, a porous silicon oxide film, which had the lowest refractive index of 1.24 at 632.8 nm, was obtained with a very high deposition rate of 235 nm/s. The reflectance and transmittance spectra showed that the low refractive index film functioned as a quarter-wave AR coating of a glass plate.
authors.affiliation: Department of Precision Science and Technology, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Nakamura
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Keiji
authors.initials: K
authors.lastname: Yokoyama
authors.forename: Kosuke
authors.initials: K
authors.lastname: Higashida
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Ohmi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kakiuchi
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Yasutake
mesh_terms: D001274:Atmospheric Pressure; D003460:Crystallization / Q000379:methods*; D008422:Materials Testing; D008567:Membranes, Artificial; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D058626:Plasma Gases / Q000737:chemistry*; D012031:Refractometry; D012822:Silicon Dioxide / Q000737:chemistry*; D013696:Temperature
chemical_list: D008567:Membranes, Artificial; D058626:Plasma Gases; D012822:Silicon Dioxide