Laser processing of metal thin films using transparent microsphere arrays

We present results on a microsphere-assisted laser processing method that allows the parallel ablation and printing of metal, leading to the formation of negative patterning (nanopinholes) and positive patterning (nanodroplets). High density packed monolayers of transparent microspheres on quartz substrates are covered with thermally evaporated silver films of controlled thickness. When back-illuminated using picosecond laser pulses, the laser interaction with the microsphere near-field mask produces periodic local detachments of the films that can be collected on a receiving substrate. We report on the resulting metal nanostructures, as our experiments lead to well-defined nanohole arrays with characteristics that can be controlled with the type of spheres and the laser energy. We characterize the ablated narrow-size-distribution nanodroplets that are randomly distributed on a receiving surface, as these aspects reveal some of the challenges associated to downscaling to the nanometer scale of laser printing techniques. (C) 2014 Elsevier B.V. All rights reserved.