Surface-enhanced Raman spectroscopy (SERS) substrates
are of utmost
interest in the analyte detection of biological and chemical diagnostics.
This is primarily due to the ability of SERS to sensitively measure
analytes present in localized hot spots of the SERS nanostructures.
In this work, we present the formation of 67 ± 6 nm diameter
gold nanoparticles supported by vertically aligned shell-insulated
silicon nanocones for ultralow variance SERS. The nanoparticles are
obtained through discrete rotation glancing angle deposition of gold
in an e-beam evaporating system. The morphology is assessed through
focused ion beam tomography, energy-dispersive X-ray spectroscopy,
and scanning electron microscopy. The optical properties are discussed
and evaluated through reflectance measurements and finite-difference
time-domain simulations. Lastly, the SERS activity is measured by
benzenethiol functionalization and subsequent Raman spectroscopy in
the surface scanning mode. We report a homogeneous analytical enhancement
factor of 2.2 ± 0.1 × 107(99% confidence interval
forN= 400 grid spots) and made a comparison to
other lithographically derived assemblies used in SERS. The strikingly
low variance (4%) of our substrates facilitates its use for many potential
SERS applications.