Micro/nanolithography of transparent thin films through laser-induced release of phase-transition latent-heat

Abstract

Large-area micro/nanolithography of transparent thin films is critical for metasurface-based optical elements, where the feature size of micro/nanostructures is generally required to be submicrometer or even nanoscale. In this work, micro/nanolith`ography through laser-induced release of phase-transition latent-heat is proposed. AgInSbTe and ZnS-SiO2 are chosen as light absorption layer and transparent thin film layer, respectively. The theoretical simulation reveals that the release of phase-transition latent-heat of AgInSbTe can heat the ZnS-SiO2 thin film to above the temperature of structural change and form micro/nanopatterns, and the thermal threshold effect of AgInSbTe thin film can confine the pattern to submicrometer or even nanoscale. The micro/nanopatterns on ZnS-SiO2 thin films can be further etched into micro/nanostructures in hydrofluoric acid solution. Using a GaN-diode-based direct laser writing lithography system, the minimum lithographic linewidth can experimentally be as low as 120 nm, which is only about 1/7 the writing spot size. The edge of obtained lithographic structure is steep and the surface is also smooth, and arbitrary lithographic structures have also been fabricated. The laser-induced release of phase-transition latent-heat is a good pathway to micro/nanolithography of transparent thin films, and has potential application in the fabrication of metasurface-based optical element.