Design and preparation of high-transmittance broadband antireflection coatings with tailored refractive indices deposited by PECVD

The design and preparation of conventional optical films are mainly limited by the refractive indices of available materials. Here, a simple-operation antireflection coatings (ARCs) design method was developed based on the tailored refractive index characteristics of thin-film materials. High-transmittance, broadband (400–800 nm), three-layer single- and double-sided ARCs with tailored refractive indices and transmittances of 99.2% and 98.5%, respectively, were designed. The sensitivity of the ARCs system was simulated, which predicts the variable range of the transmittance affected by the random manufacturing errors in the refractive index (±0.5%) and film thickness (±2.5%) of each layer. The ARCs consisted of nonstoichiometric silicon oxynitride and silicon nitride films formed on glass substrates by PECVD techniques. The crystallite state, relative atomic concentration, and Si-centered tetrahedral phase Si–Si4-(ν+η)OνNη of each layer were determined. The morphology images of top and cross-section views and elemental mapping of ARCs were displayed. The designed and measured transmittances were compared; the average transmittance deviations of the single- and double-sided amorphous ARCs over the visible were 0.1% and 0.4%, respectively, which show good agreement. Furthermore, the reproducibility, repeatability, and stability of PECVD were evaluated. These results are detail discussed and are expected to serve as a reference for the preparation of optical films formed via PECVD.