Design and sol-gel preparation of SiO2/TiO2 and SiO2/SnO2/SiO2-SnO2 multilayer antireflective coatings

摘要

Interference-type antireflective coatings with homogeneous multilayers have been designed and prepared. Optical thin film design of a 6-layer SiO2/TiO2 and a tri-layer SiO2/SnO2/SiO2-SnO2 was investigated. The optical constants of the source materials for optical design were directly extracted from the sol-gel-prepared oxide thin films. The designed 6-layer SiO2/TiO2 exhibits a high average transmittance (98.3%) over a large bandwidth (400-700 nm) compared to a starting lambda/4-lambda/2 stack of SiO2/TiO2. Sol-gel coating of sub-10 nm ultrathin film for the multilayer was circumvented by employing diluted sols. A lambda/4-lambda/4-lambda/4 stack of SiO2/SnO2/SiO2-SnO2 was also constructed, with its antireflective performance optimized by tuning the refractive index of the SiO2-SnO2 composite layer. In spite of some thickness deviation from the design value, a peak transmittance of 98.2% and 98.6% has been reached for the sol-gel SiO2/TiO2 and SiO2/SnO2/SiO2-SnO2 multilayers, respectively. The results obtained in this work demonstrate the great advantage of combining design with sol-gel preparation for antireflective coatings. (C) 2017 Elsevier B.V. All rights reserved.