Sep 26, 2011
Playing Lego bricks with nanostructures
Scientists have demonstrated a fast and easy nanoimprint lithography (NIL)-based process for stacking negative index structures such as fishnet and Swiss-cross metamaterials. Materials are referred to as negative index materials (NIMs) when the designed structures provide resonances for the electric and magnetic field such that negative refraction occurs. 3D negative index materials promise to enable numerous novel and breakthrough applications like perfect lenses and cloaking devices. Developers are looking to fabricate such structures with a fast and cost-efficient technique over large areas, which suits industrial production.
Nanoimprint lithography (NIL) allows the patterning of large areas within a few seconds using a nanostructured stamp. First, single functional NIM layers were fabricated on silicon substrates using a two-layer lift-off process. Next, these single layers were peeled off from the substrate using a UV-curable hybrid polymer Ormocomp as "glue". Repeating this process several times and stacking the single layers on top of each other leads to 3D NIM.
The stacking process can be performed on quartz, glass and also flexible substrates and takes only a few minutes. It is applicable to a very wide and general class of nanostructured thin films as well as optical metamaterials.
The group has demonstrated NIMs with a resonance frequency in the infrared. Further experiments will follow to achieve 3D NIMs within the visible regime.
Additional information can be found in the journal Nanotechnology.
About the author
Most of the work was carried out within the EC Project NIM_NIL no. 228637 (www.nimnil.org) and within the national project NILmeta (www.nilaustria.at). Iris Bergmair is based at PROFACTOR GmbH. She coordinates the projects and has been working in the field of nanoimprint lithography since 2006. The results of this study were obtained by cooperation between different partners: Iris Bergmair, Michael Mühlberger and Rainer Schöftner from PROFACTOR GmbH fabricated the structures by NIL. Babak Dastmalchi, Michael Bergmair and Kurt Hingerl simulated the structures, SEM images were taken by Guenter Hesser and Ahmad Saeed, and Wolfgang Hilber performed thin-film deposition for test samples. Christian Helgert, Ekaterina Pshenay-Severin, Bernhard E Kley and Thomas Pertsch from the University of Jena, Germany, fabricated NIL stamps and characterized the NIMs by transmission and reflection measurements. Uwe Hübner from the Institute of Photonic Technology, Jena, deposited the thin films for the NIM samples. Nian-hai Shen, Raluca Penciu, Maria Kafesaki and Costas Soukoulis from the Foundation for research and technology Hellas, University of Crete, Greece, calculated the NIM properties.