AN IMPROVED CONTROL TECHNIQUE FOR THE ELECTROCHEMICAL FABRICATION OF SCANNING-TUNNELING-MICROSCOPY MICROTIPS

The electrochemical etching technique has been widely used in the fabr ication of microtips. In this article, an improved feedback control te chnique for the de electrochemical fabrication of scanning tunneling m icroscopy microtips is presented. Distinguished from the conventional control techniques. this newly developed method directly uses the etch ing current as the only control signal instead of comparing it with th e reference current. Therefore, the control process is more accurate. The tungsten tips with radius of curvature down to 20 nm can be produc ed reproducibly. By varying the cutoff time of the control circuit, ti ps with different radii of curvature can be fabricated. (C) 1997 Ameri can Institute of Physics.