Ultrafast direct imprinting of nanostructures in metals by pulsed laser melting

We report a method of one-step direct patterning of metallic nanostructures. In the method, termed laser assisted direct imprinting (LADI), the surface of a metal film on a substrate is melted by a single excimer laser pulse and subsequently imprinted within approximately 100 ns using a transparent quartz mold, while the substrate is kept at a low temperature and in a solid phase. Using LADI, we imprinted gratings with approximately 100 nm linewidth, 100 nm depth, and 200 nm pitch, as well as isolated mesas of approximately 20 microm size, in Al, Au, Cu and Ni thin films. We found that the quartz mold was able to imprint metals even at temperatures higher than its melting point. The technique could be extended to other metals regardless of their ductility and hardness, and would find applications in photonic and plasmonic device production.