Mvh. Rao et Bk. Mathur, SHARP TUNGSTEN TIPS FOR SCANNING TUNNELING MICROSCOPE PREPARED BY ELECTROCHEMICAL ETCHING PROCESS, Indian Journal of Pure & Applied Physics, 31(8), 1993, pp. 574-576
Tips for scanning tunnelling microscope (STM) are now more frequently
made by electrochemical etching of tungsten wire in an aqueous solutio
n of an alkaline base. In this method it is observed that to get a sha
rp tip the etching voltage has to be cut off as quickly as possible wh
en there is a sudden drop in etch current. We have designed an electro
nic circuit that can cut off the voltage within a time limit of 500 ns
and employed it successfully to get very sharp tips with a radious of
curvature of less than 1000 angstrom. Tips produced by this process h
ave been characterized by scanning electron microscope (SEM) and are u
sed successfully for STM applications. Atomic resolution image of (000
1) surface of graphite scanned with these tips is given as an example.