Etching gold tips suitable for tip-enhanced near-field optical microscopy.

We describe a simple method of fabricating gold tips for tip-enhanced near-field optical microscopy using a single step direct current electrochemical etch. Smooth gold tips with a radius of curvature approximately 40 nm and with an aspect ratio suitable for shear force measurement have been produced in a few minutes. A detailed analysis of the etching process has enabled production of reproducible high quality tips. Near field images of single quantum dots using tips etched with this technique are shown.