Etching an STM Tip

1. Set up a 1M solution of KOH (.5 L of DI water and 56 g of KOH pellets).
2. Find tungsten wire of a diameter that matches your tip holder.
3. You want to make a stand with some sort of fine adjustment for holding the tungsten wire.
4. Using an AC power supply, connect one voltage to the wire you will etch. Connect the other to a metal/wire loop you will dip in solution.
5. Barely just dip with tip into the solution by using the fine adjustment and back out of the solution a bit so that the tip is just barely submersed in the surface (pulled upwards via capillary action).
6. Turn the voltage on (4-14V, but you can play around with this to see what works) and leave for about 4 minutes.
7. When the wire breaks, turn off the voltage. Collect the bottom tip using tweezer to pick it up from the solution.  Snip the top tip off with cutters.

Setup (from http://goliath.emt.inrs.ca/surfsci/docs/sc04/Olfert.pdf)

More information than you could ever really want here.