Production of centimeter-scale sub-wavelength nanopatterns by controlling the light path of adhesive photomasks

Abstract

The capability of generating sub-wavelength nanostructures in a low-cost and high yield fashion is important for many areas of research. In this work, a facile parallel near-field photolithography strategy was developed to enable centimeter-scale nanopatterns with sub-wavelength feature size and variable feature shapes by utilizing a metal coating to manipulate the light path of polydimethylsiloxane (PDMS) structure based photomasks. The thin metal coating and microscale apertures created on PDMS structures not only imparted the adhesive and conformal merits to the elastomeric photomasks, but are also capable of making the nanoscale regions below V-shape PDMS tips apexes or vertical sidewalls of flat PDMS reliefs be selectively exposed by controlling the light path. Thus, sub-100 nm nanostructures were generated over large areas on the substrate. For the first time, two under exposures in near-field photolithography were employed to fabricate sub-wavelength nanorod arrays with adjustable length to width ratios by rotating the photomask in the second exposure. Besides generation of the smallest 70 nm photoresist features and 80 nm metal nanostructures, this technique was also exploited to fabricate self-assembled monolayers (SAMs) molecular nanopatterns with sub-wavelength feature size. This nanolithography strategy combines the advantages of low-cost, high productivity, sub-wavelength feature size and flexible feature geometries, making it a facile and general nanofabrication tool to enable various functional nanostructures for academic research.