Non-invasive fabrication of plasmonic nanostructures on dielectric substrates coated with transparent-conductive oxide

Abstract

Modern photonics demands for high-resolution (HR) and deterministic lithography on transparent substrates. Thermal scanning-probe lithography (t-SPL) is a mask-less approach that couples a nanoscopic patterning resolution with the possibility to perform morphological characterizations without damaging delicate substrates unlike it happens for other techniques of similar resolution. In order to operate at its maximum performances, an electric bias between the scanning micromachined cantilever and the sample is needed thereby preventing, in principle, the patterning of transparent materials (that are usually insulators). In this work we demonstrate that by intercalating an ultrathin layer of a transparent conductive oxide (TCO) between an insulating and transparent substrate and the polymeric thin layer it is possible to exploit all the benefits of t-SPL also on challenging optically transparent substrates. Taking advantage of this particular lithographic configuration, we were effectively able to obtain a family of different gold plasmonic nanostructures resonating in the spectral range from the Visible to the Near-Infrared. The ensemble of the different resonators shows optical properties that encourage their exploitation in fields like sensing and thermoplasmonics.