Ultrasmooth Patterned Metals for Plasmonics and Metamaterials
Prashant Nagpal,1
Nathan C. Lindquist,2
Sang-Hyun Oh,2
David J. Norris1,*
Surface plasmons are electromagnetic waves that can exist at
metal interfaces because of coupling between light and free
electrons. Restricted to travel along the interface, these waves
can be channeled, concentrated, or otherwise manipulated by
surface patterning. However, because surface roughness and other
inhomogeneities have so far limited surface-plasmon propagation
in real plasmonic devices, simple high-throughput methods are
needed to fabricate high-quality patterned metals. We combined
template stripping with precisely patterned silicon substrates
to obtain ultrasmooth pure metal films with grooves, bumps,
pyramids, ridges, and holes. Measured surface-plasmon–propagation
lengths on the resulting surfaces approach theoretical values
for perfectly flat films. With the use of our method, we demonstrated
structures that exhibit Raman scattering enhancements above
10
7 for sensing applications and multilayer films for optical
metamaterials.
2 Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
* To whom correspondence should be addressed. E-mail: dnorris{at}umn.edu
