title: Remarkable birefringence in a TiO2-SiO2 composite film with an aligned mesoporous structure.
abstract: Mesoporous titania-silica composite films with highly aligned cylindrical pores are prepared by the sol-gel method using a substrate with structural anisotropy. The strong alignment effect of a rubbing-treated polyimide film on a substrate provides a narrow alignment distribution in the plane of the film regardless of the fast condensation rate of titania precursors. The collapse of the mesostructure upon the surfactant removal is effectively suppressed by the reinforcement of the pore walls with silica by exposing the as-deposited film to a vapor of a silicon alkoxide. The existence of a silica layer on the titania pore wall is proved from the distributions of Ti and Si estimated by the elemental analysis in high resolution electron microscopy. The obtained mesoporous titania-silica composite film exhibits a remarkable birefringence reflecting the highly anisotropic mesoporous structure and the high refractive index of titania that forms the pore wall. The Δn value estimated from the optical retardation and the film thickness is larger than 0.06, which cannot be achieved with the conventional mesoporous silica films with uniaxially aligned mesoporous structure even though the alignment of the pores in the films is perfect. These inorganic films with mesoscopic structural anisotropy will find many applications in the field of optics as phase plates with high thermal/chemical/mechanical stabilities.
authors.affiliation: Frontier Research Center, Canon Inc., 3-30-2 Shimomaruko, Ohta-ku, Tokyo 146-8501, Japan. miyata.hirokatsu@canon.co.jp
authors.forename: Hirokatsu
authors.initials: H
authors.lastname: Miyata
authors.forename: Yuta
authors.initials: Y
authors.lastname: Fukushima
authors.forename: Kohei
authors.initials: K
authors.lastname: Okamoto
authors.forename: Masahiko
authors.initials: M
authors.lastname: Takahashi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Watanabe
authors.forename: Wataru
authors.initials: W
authors.lastname: Kubo
authors.forename: Atsushi
authors.initials: A
authors.lastname: Komoto
authors.forename: Shin
authors.initials: S
authors.lastname: Kitamura
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Kanno
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Kuroda