Mar 6, 2013
UV curing prints photonic nanodevices
Researchers at aBeam Technologies and the Molecular Foundry at Lawrence Berkeley National Laboratory in the US have developed a new and robust way to fabricate printable nanophotonic structures with a high refractive index and sub-10 nm resolution. The nanostructures are directly imprinted onto a functional titania-based resist film using an ultraviolet curing technique. The process opens the way to fabricating low-cost printable photonic integrated devices.
Nanoimprint Lithography (NIL) is a promising technique for fabricating high-throughput, high-performance printable nanodevices. We have demonstrated that NIL is suitable for making large-area nanophotonic structures with high refractive index and good optical transparency.
We developed a specific hybrid organic-inorganic NIL resist for imprinting large-area films in a robust process that allows us to pattern functional films over large areas without the cracks inherent in sol-gel films. Optical titania-based resist films are directly imprinted at low pressure with UV light for two minutes – a process that allows to imprint sub-10 nm titania structures in a new state-of-the-art technique.
The optical properties of the imprinted films are controlled by a post-annealing treatment. We measured a refractive index and optical transparency for the nanostructures as high as 2.1 and 95% respectively in the visible wavelength range. We have already tested simple imprinted structures and have shown that the process is suitable for making photonic devices and creating novel nanophotonic structures.
Our approach could help in the development of novel applications based on photonic nanostructures and open the way to printable photonic devices. We believe that direct imprinting of functional films at the nanometre scale opens up a lot of opportunities and that it could one day it be used to fabricate printable integrated nanophotonic devices.
More information about the technique can be found in the journal Nanotechnology.
About the author
The work was led by Dr Christophe Peroz and Dr Stefano Cabrini at the Molecular Foundry, LNBL, in Berkeley, California. The Molecular Foundry is one of five United States Department of Energy (DOE) Nanoscale Science Research Centers, national user facilities for interdisciplinary research at the nanoscale, supported by the DOE Office of Science. The nanoimprint technology was developed by Carlos Pina Hernandez, research scientist and Christophe Peroz, Director at aBeam Technologies Inc. Masters student Valeria Lacatena helped to develop the imprint process; the etching process was developed by Deirdre Olynick, and Giuseppe Calafiore, also master students. Optical characterization of the printed structures was carried out by Konstantin Kravtsov, Alexander Goltsov and Vladimir Yankov, scientists at NanoOptic Devices. Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under contract no. DE-AC02- 05CH11231. The work is also supported by the Air Force Office of Scientific Research (AFOSR), Air Force Material Command, USAF, under grant/contract number FA9550-12-C-0055 in the framework of a STTR project.