Fabrication of silica nanopillars by templated etching using bimetallic nanoparticles for anti-reflection applications

We report on the anti-reflection characteristics of silica nanopillars fabricated using bimetallic copper-silver nanoparticles as an etch mask. The particles were formed by dewetting and their size and shape were controlled by the film thickness and annealing conditions. Our results showed that annealing of a copper-silver film results in formation of segregated bimetallic nanoparticles. Using these bimetallic nanoparticles as a mask for reactive ion etching produced dual diameter nanopillars, compared to single diameter nanopillars for monometallic nanoparticles. The height and shape of the nanopillars were controlled by the initial film thickness, annealing temperature, and etching parameters. The fabricated silica nanopillars showed a reduction in reflectance as compared to the bare substrate in the UV–Vis-NIR range, and dual diameter nanopillars were better as compared to single diameter nanopillars. Increasing etch duration resulted in increase in pillar height and a further reduction in reflectance. These silica nanopillar structures can be used as anti-reflection coatings.