Electrochemical Etching Method to Fabricate Tips for Scanning Tunnelling Microscopes using Tungsten

Abstract

The goal of this project was to create a tungsten tip for use in STM machines. This project started with the research of existing methods for creating STM tips through electrochemical etching. During initial testing, the electrolyte solution was identified as a powerful variable. Once a suitable solution had been found and optimized, we made changes to the etching procedure while observing the difference between outcomes. In this way we developed a method, which could create consistently sharp tips. The focus moved from finding a method for constant power etching to pulse etching. The advantage of constant power etching was that it gave a good indication of how sharp the tips could get while being very fast, allowing for rapid testing of variables and their impact on the outcome. The advantage of pulsed etching was the ability to control how sharp the tips created were. The final procedure was to pass 4V through the equipment (see figure 9), pulsed on for 1 second and off for 8 seconds. When the wire breaks the voltage is to be turned off and the tip retrieved. Excellent tips have been produced using this method, as evidenced in this report.