Sharka Prokes, NRL
There is significant interest in the growth of semiconductor nanowires, due to interesting and useful optical, electrical and mechanical properties. They are attractive for a variety of applications, including optical sensing. One of the interesting aspects of these nanostructures is an enhanced plasmonic response, which has been investigated using Surface Enhanced Raman Spectroscopy (SERS). The growth and formation of several nanowire/metal composite structures, the formation of random and ordered arrays of these structures, and their surface enhanced Raman (SERS) properties will be discussed. The effect of geometry will also be examined, and we will show, both experimentally and in electric field simulations, that the intersections of these nanowires are critical in generating the high electric fields necessary for this enhancement.
In addition, we recently developed another novel plasmonic material, based on Plasma Enhanced Atomic Layer Deposition (PEALD) of Ag, which results in strong plasmonic properties of flat Ag films. It will be shown as-deposited flat PEALD Ag films exhibit unexpected plasmonic properties and the plasmonic enhancement can differ significantly, depending on the microstructure of the Ag film. Electric field simulations suggest that the plasmonic behavior is due to air gaps that are an inherent property of the PEALD growth of Ag and account for the trends observed in SERS. This unusual plasmonic behavior is very similar to what would be expected in hybrid spoof plasmonics and suggests that PEALD Ag is a metamaterial.