Study on the Hydrophobic Modification of MTES/NH₃ Vapor Surface Treatment for SiO₂ Broadband Anti-Reflection Coating

In this article, ammonia and methyltriethoxysilane (MTES) were chosen as vapor phase modifiers for the base-catalyzed SiO2 film. The surface of the film became more dense because of the hydroxyl condensation under the catalyst of ammonia, while the introduction of methyl groups by MTES of vapor treatment hindered the condensation to avoid over-change in film thickness. The hydrophobic of film was improved while the surface roughness of the film increased after treatment. The treated double-layer broadband anti-reflection (AR) coating retains high optical properties with the transmittance of 99.61%, 98.85%, and 99.16% at 355 nm, 532 nm, and 1064 nm, respectively. After exposing to the high humidity condition for 30 days, the broadband AR coating after treatment shows good optical durability, and the transmittance at 355 nm only drops by 0.12%. This vapor surface treatment can find potential application in high-power laser systems and solar cells.