Reproducible electrochemical etching of silver probes with a radius of curvature of 20 nm for tip-enhanced Raman applications

The performance of tip-enhanced Raman spectroscopy (TERS) largely depends on probe optimisation. An electrochemical etch using nitric acid and ethanol produces sharp silver probes with radius of curvature between 20 and 60 nm. Optimisation also identified controllable tapers; rough or smooth. Boundary element method simulations comparing the response to 532 nm excitation of silver and gold probes reveal no discernable field enhancement at the gold apex, but strong localised enhancement is observed at the silver apex. The motivation for employing this method of etching silver probes can also be seen in the signal enhancement observed in preliminary TERS data presented. (C) 2011 American Institute of Physics. [doi:10.1063/1.3646106]