Anisotropic nanoscale wrinkling in solid state substrates

Abstract

Pattern formation induced by wrinkling is a very common phenomenon exhibited in soft-matter substrates. In all these systems wrinkles develop in presence of compressively stressed thin films lying on compliant substrates. Here we demonstrate the controlled growth of self-organized nanopatterns exploiting a wrinkling instability on a solid-state substrate. Soda-lime glasses are modified in the surface layers by a defocused ion beam which triggers the formation of a compressively stressed surface layer deprived of alkali ions. When the substrate is heated up near its glass transition temperature, the wrinkling instability boosts the growth rate of the pattern by about two orders of magnitude. High aspect ratio anisotropic ripples bound by faceted ridges are thus formed which represent an optimal template for guiding the growth of large area arrays of functional nanostructures. We demonstrate the engineering over large square cm areas of quasi-1D arrays of Au nanostripe dimers endowed with tunable plasmonic response, strong optical dichroism and high electrical conductivity. These peculiar functionalities allow to exploit these large area substrates as active metamaterials in nanophotonics, biosensing and optoelectronics.