Pattern transfer, self-organized surface nanostructuring, and nanodrilling of sapphire using nanosecond laser irradiation

Abstract

Nanostructures have a widespread field of applications. The structuring of sapphire assisted by a nanosecond laserinduced self-organized molten molybdenum layer deformation process was studied. At low laser fluence the irradiation of a thin metal layer on dielectric surface results in a melting and nanostructuring of the metal layer and partially of the dielectric surface. Furthermore, a subsequent high laser fluence treatment of the metal nanostructures results in different features: (i) pattern transfer, (ii) self-organized surface nanostructuring, and (iii) nanodrilling. (i) Pattern transfer: The irradiation of the pre-structured metal layer with high laser fluences allows the transfer of the lateral geometry of the metal nanostructures into the dielectric surface. (ii) Self-organized surface nanostructuring: The multi-pulse irradiation of the metal layer/dielectric system with moderate laser fluences results in a selforganized nanostructuring of the dielectric surface. (iii) Nanodrilling: The multi-pulse low laser fluence irradiation of the metal layer results in the formation of metal droplets and a further high fluence irradiation of the laser-generated metal droplets results in a stepwise evaporation of the metal and in a partial evaporation of the dielectric and, finally, in the formation of cone-like holes. The resultant structures were investigated by scanning electron microscopy (SEM).