Nano-imprinting of surface relief gratings on soda-aluminosilicate and soda-lime silicate glasses

One-dimensional gratings of 700-nm period were imprinted on a sodaaluminosilicate glass (NAS) and a soda-lime silicate glass (NCS) using a platinum-coated SiO₂ mold with application of DC voltage. The migration of network modifier cations below the anode side surface to the cathode side is a necessary condition for grating formation. Glass surfaces were chemically etched using a 55% KOH solution at 70°C. The top area of the NAS grating ridge, where the non-contacted area of the mold is located, was etched preferentially. Finally, the reverse concavo-convex grating appeared by etching. Localized stress corrosion in the grating ridge is expected to be an origin of the anisotropic etching and the grating pattern formation. In contrast, such anomalous etching behavior was not observed for the NCS. The bottom of the grating groove, the mold contacted area, was etched monotonously, maintaining the initial sinusoidal grating shape.