Since then, many superior techniques have been developed for manufacturing probes for scanning tunneling microscopes. The most common method utilizes electrochemical etching. The tunneling probes need an extremely small radius of curvature at the tip. Ideally, the probe needs atomic or near atomic sharpness. Also, the probes need to be short and rigid to prevent vibrations.
Electrochemical etching produces very sharp probes.
With this technique tungsten probes with radii or curvature of less than one micron can be produced. The etching process also forms an oxide coating on the surface of the probe. This oxide prevents tunneling current from flowing, causing the probe to crash into the sample. The oxide must be removed prior to using the probe. A simple solution to this problem is to gently crash the probe into the sample so that the oxide breaks, allowing current to flow.