Porous MgF2 antireflective λ/4 films prepared by sol–gel processing: comparison of synthesis approaches

Abstract

Porous MgF 2 is a highly promising film material for the preparation of durable antireflective coatings. Synthesis routes based on Mg(OMe) 2 and Mg(OAc) 2 precursors are described, and the resulting sol-gel films and their thermal consolidation are compared using thermal analysis (TGA/DTA), scanning electron microscopy, ellipsometric porosimetry and X-ray diffraction. Due to their constant viscosity, Mg(OAc) 2 -based coating solutions are superior from the practical point of view. The porous films are stable against degradation under the steady-state temperature humidity life test (85/85), and they can successfully be integrated into TiO 2 -MgF 2 -TiO 2 interference filters. Graphical Abstract Porous MgF 2 antireflective k/4 coatings were prepared by sol-gel processing. Synthesis routes based on Mg(OMe) 2 and Mg(OAc) 2 precursors are established, and the properties of the resulting film materials are compared, respectively.

Sol-Gel-Synthesis of Nanoscopic Complex Metal Fluorides

“…The fluorolytic sol-gel synthesis of binary metal fluorides (HS-AlF 3 , MgF 2 , and CaF 2 ) derived from different metal precursors such as metal alkoxides, [18,19] metal acetates [20], and metal chlorides [21,22] allows access to monodisperse nanoscopic particles with a broad range of potential applications including optic, catalysis, and ceramic [23]. Notably, we succeeded in the synthesis of transparent and long-time stable CaF 2 sols prepared from calcium ethoxide and calcium isopropoxide for the first time just by increasing the polarity of the solvent in the CaF 2 system.…”

Sol–gel preparation of moisture-resistant antireflective coatings from novel hollow silica nanoparticles

“…It is noteworthy that the rate of MTES hydrolysis is much higher than its condensation due to the steric hindrance effect [19]. In the MTES/TEOS onestep base-catalyzed method, when MTES and TEOS were added into the reaction solution, the hydrolysis reaction will be initiated immediately, whereas the condensation may take place in three different ways: (a) self-condensation of hydrolysis products of TEOS (Si(OH) 4 ); (b) cocondensation between Si(OH) 4 and hydrolysis products of MTES (CH 3 -Si(OH) 3 ); and (c) self-condensation of CH 3 -Si(OH) 3 . The self-condensation rate of CH 3 -Si(OH) 3 may proceed much slowly than that of (b) owing to the aforementioned steric hindrance effect.…”

“…Antireflective (AR) coatings are required to improve the light transmission in a wide variety of applications [1][2][3]. The principle of single-layer AR coatings is based on the destructive interference between the air-coating and the coating-substrate interfaces.…”

Porous MgF2-over-gold nanoparticles (MON) as plasmonic substrate for analytical applications

“…In particular, we decided to combine the favourable properties of immobilized gold nanoparticles with the optical and mechanical properties of nanoscopic magnesium uoride. Magnesium uoride, commonly applied in antireective coating, exhibits a particularly low refractive index (n MgF 2 ¼ 1.38, for comparison n SiO 2 ¼ 1.50 and n Al 2 O 3 ¼ 1.78) 16,17 and shows high transmittance across the UV-Vis to IR range ($100 nm to $8 mm). 18,19 Moreover, the properties of magnesium uoride layers, including porosity, can be controlled by the calcination temperature and the applied magnesium precursor.…”

“…18,19 Moreover, the properties of magnesium uoride layers, including porosity, can be controlled by the calcination temperature and the applied magnesium precursor. 16 Magnesium uoride lms are mechanically very resistant, e.g., even against steel wool. 19 These interesting optical and mechanical properties of magnesium uoride lms lead us to expect that it might be a benecial compound in a plasmonic substrate.…”