Note: Controlling the length of plasmonic tips obtained by pulsed electrochemical etching.

We present a method to control the length of plasmonic gold tips through pulsed electrochemical etching. This method uses a cut-off circuit to interrupt the etching when the desired length is achieved, paving the way to tune the plasmonic properties of these tips through their shape. The control of the tip length by monitoring the cell voltage is the result of a study of the etching dynamics. The resulting tips possess a low apex radius and a small opening angle, allowing for high spatial resolution both in topography and in near-field imaging. The plasmonic behavior was confirmed in tip-enhanced Raman spectroscopy.