Nanomorphology and SERS activity in plasma prepared silver surfaces

A plasma oxidation-reduction process has been found to be suitable for producing silver surfaces showing surface enhanced Raman (SERS) activity. SERS spectra of monodisperse polystyrene films have been obtained by using these surfaces in order to study the correlation between enhancement and nanomorphology as probed by atomic force microscopy. It was found that the enhancement is strongly correlated with a coalescence of the initially present silver grains (10–50 nm in size). This coalescence leads to the formation of 100–300 nm silver hills in which each silver grain is still clearly distinguishable. The increase in the effective surface area due to the particle coalescence has been correlated to the SERS enhancement in straightforward fashion.