title: Sequential Infiltration Synthesis for the Design of Low Refractive Index Surface Coatings with Controllable Thickness.
abstract: Control over refractive index and thickness of surface coatings is central to the design of low refraction films used in applications ranging from optical computing to antireflective coatings. Here, we introduce gas-phase sequential infiltration synthesis (SIS) as a robust, powerful, and efficient approach to deposit conformal coatings with very low refractive indices. We demonstrate that the refractive indices of inorganic coatings can be efficiently tuned by the number of cycles used in the SIS process, composition, and selective swelling of the of the polymer template. We show that the refractive index of Al2O3can be lowered from 1.76 down to 1.1 using this method. The thickness of the Al2O3coating can be efficiently controlled by the swelling of the block copolymer template in ethanol at elevated temperature, thereby enabling deposition of both single-layer and graded-index broadband antireflective coatings. Using this technique, Fresnel reflections of glass can be reduced to as low as 0.1% under normal illumination over a broad spectral range.
authors.affiliation: Materials Science and Engineering Department, University of North Texas , Denton, Texas 76203 United States.
authors.forename: Diana
authors.initials: D
authors.lastname: Berman
authors.affiliation: Institute for Molecular Engineering, University of Chicago , Chicago, Illinois 60637 United States.
authors.forename: Supratik
authors.initials: S
authors.lastname: Guha
authors.forename: Byeongdu
authors.identifier: 0000-0003-2514-8805
authors.initials: B
authors.lastname: Lee
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Elam
authors.affiliation: Institute for Molecular Engineering, University of Chicago , Chicago, Illinois 60637 United States.
authors.forename: Seth B
authors.initials: SB
authors.lastname: Darling
authors.forename: Elena V
authors.identifier: 0000-0002-5565-2060
authors.initials: EV
authors.lastname: Shevchenko
keywords: antireflective; block copolymer; low refractive index; polymer swelling; porous; sequential infiltration synthesis