Note: Electrochemical etching of sharp iridium tips

We describe an etching procedure for the production of sharp iridium tips with apex radii of 15-70 nm, as determined by scanning electron microscopy, field ion microscopy, and field emission measurements. A coarse electrochemical etch followed by zone electropolishing is performed in a relatively harmless calcium chloride solution with high success rate. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3662473]