Anisotropic Nanoscale Wrinkling in Solid-State Substrates.

Pattern formation induced by wrinkling is a very common phenomenon exhibited in soft-matter substrates. In all these systems, wrinkles develop in the presence of compressively stressed thin films lying on compliant substrates. Here, the controlled growth of self-organized nanopatterns exploiting a wrinkling instability on a solid-state substrate is demonstrated. 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. The engineering over large square centimeter areas of quasi-1D arrays of Au nanostripe dimers endowed with tunable plasmonic response, strong optical dichroism, and high electrical conductivity is demonstrated. These peculiar functionalities allow these large-area substrates to be exploited as active metamaterials in nanophotonics, biosensing, and optoelectronics.