Ultralow Index\nSiO₂ Antireflection Coatings Produced via Magnetron Sputtering

Abstract

Antireflection (AR) coatings with graded refractive index\nprofiles\napproaching air offer unparalleled AR performance but lack a scalable\nfabrication process that would enable them to be used more widely\nin applications such as architecture and solar energy conversion.\nThis work introduces a sputtering-based sacrificial porogen process\nto fabricate multilayer nanoporous SiO₂ coatings with tunable\nrefractive index down to <i>n</i>_eff = 1.11.\nUsing this approach, we demonstrate a step-graded bilayer AR coating\nwith outstanding wide-angle AR performance (single side average reflectivity\nin the visible spectrum ranges from 0.2% at normal incidence to 0.7%\nat 40°), good adhesion, and promising environmental durability.\nThese results open up a path to produce ultrahigh performance AR coatings\nover large area by using industrial-scale magnetron sputtering systems.