title: Films Consisting of Innumerable Tapered Nanopillars of Mesoporous Silica for Universal Antireflection Coatings.
abstract: Films with a fine structure consisting of innumerable nanopillars of mesoporous silica (MPS) are formed by a reactive ion etching process with a fluorine-containing gas. Each nanopillar has a tapered shape with a uniform height, which effectively suppresses reflection by the formation of an ideal graded refractive index structure. The nanopillars are spontaneously formed under low-pressure conditions, wherein locally deposited Al-F compounds, originating from an alumina plate in the etching chamber, work as a fine etching mask. The high etching rate of the MPS film allows a very high aspect ratio of the nanopillars. The refractive index of the MPS nanopillars can be universally tuned by a controlled incorporation of TiO2 into the mesopores, which results in effective reduction of reflectance on a given substrate. The outstanding antireflection performance is experimentally demonstrated for glass substrates with a wide refractive index range.
authors.affiliation: Corporate R&D Headquarters, Canon Inc., 3-30-2, Shimomaruko, Ohta-ku, Tokyo, 146-8501, Japan. miyata.hirokatsu@canon.co.jp.
authors.forename: Hirokatsu
authors.identifier: http://orcid.org/0000-0002-6698-7237
authors.initials: H
authors.lastname: Miyata
authors.affiliation: Corporate R&D Headquarters, Canon Inc., 3-30-2, Shimomaruko, Ohta-ku, Tokyo, 146-8501, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Kitamura
authors.affiliation: Corporate R&D Headquarters, Canon Inc., 3-30-2, Shimomaruko, Ohta-ku, Tokyo, 146-8501, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Corporate R&D Headquarters, Canon Inc., 3-30-2, Shimomaruko, Ohta-ku, Tokyo, 146-8501, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Takahashi
keywords: mesoporous materials; nanostructures; refractive index matching; silicates; thin films