High aspect-ratio sub-500 nm UV-PDMS bilayer stamps by means of hybrid thermal-ultraviolet curing for resonant nanopillars fabrication through soft UV-NIL

A novel protocol for the fabrication of bilayer stamps for soft UV-NIL is presented. The patterned layer is composed of a commercially available UV-curable PDMS, while a quartz backplane acts as support layer. The pattern reproduced in the stamp through direct casting comes from a hard template and is composed of nanopillar arrays with 250–300 nm of diameter and 300–400 nm in height. The master template with nanoholes is treated with a self-assembled monolayer before pattern reproduction for improved separation of UV-PDMS layer. The hybrid cross-linking protocol includes a thermal and a UV process, and parameters of the former are investigated for best results. The pattern was reproduced in a resist on a Si sample by means of soft UV-NIL, and the imprinted nanohole arrays show dimensions coherent with the stamp. Finally, its application in the fabrication of resonant nanopillars for sensing purposes is briefly described. This is, to the best of our knowledge, the first time a hybrid thermal-ultraviolet curing of UV-PDMS has been reported and that protruding nanostructures with aspect-ratio higher than 1 in soft UV-NIL stamps have been demonstrated.