  The surface-enhanced Raman scattering (SERS) signal from an AgFON plasmonic
substrate, recoated with benzenethiol, was observed to increase by about 100%
upon heating for 3.5 min at 100C and 1.5 min at 125C. The signal intensity was
found to increase further by about 80% upon a 10 sec exposure to a
high-intensity (3.2 kW/cm^2) 785-nm cw laser, corresponding to 40 mW in a
40+/-5-um diameter spot. The observed increase in the SERS signal may be
understood by considering the presence of benzenethiol molecules in an
intermediate or 'precursor' state in addition to conventionally ordered
molecules forming a self-assembled monolayer. The increase in the SERS signal
arises from the conversion of the molecules in the precursor state to the
chemisorbed state due to thermal and photo-thermal effects.
