Laser direct nano-structuring assisted by water droplets

Abstract

Nano-structuring using laser direct writing technology has shown a great potential for industrial applications. A novel application of water droplets to this technology is proposed in this paper. With a hydrophobic layer and a controlled substrate temperature, a layer of randomly distributed water droplets with a high contact angle is formed on the substrate. These liquid droplets can be used as lenses to enhance the laser intensity at the bottom of the droplets. As a result, nanoscale holes can be fabricated on the substrate by controlling the laser energy density. We successfully fabricate holes with a diameter of 600nm at a substrate temperature of 12°C and a power density of 1.2×108 mW/cm2 in our experiments.