Surface-enhanced Raman scattering (SERS) is emerging
as a powerful technique for the trace level detection
of various biological and chemical species and is
believed to make a huge impact in life sciences, environmental
monitoring, and homeland security (1-7). Numerous
SERS substrates from roughened noble metal surfaces
to e-beam patterned metal nanostructures with enhancement
factors ranging from 1 × 104 to 1 × 1010 have been
demonstrated over the last two decades (6, 8-11).