Electrochemical etching using surface carboxylated graphite electrodes in ultrapure water

Electrochemical etching enables processing with an atomic-level accuracy, without deteriorating the physical properties of the workpiece; however, contamination of its surface with electrolytes is unavoidable. If it is possible to carry out electrochemical etching without using electrolytes, such a process will be applicable to electronic device manufacturing and precision nanoscale processing of semiconductor materials. In addition, this process does not require the use of chemicals, cleaning after processing or disposal of waste fluid, which results in a low-cost and environmentally friendly process. To develop an electrochemical etching process that does not require the use of electrolytes, we proposed a method in which a functional-group-modified electrode is used as the cathode. A carboxylated graphite electrode was prepared by treating a graphite electrode with sulfuric acid. Electrolysis of ultrapure water was carried out using the obtained electrode as a cathode. The results indicate that the electrolysis current obtained using the modified electrode is approximately six-fold that obtained using an unmodified electrode. Furthermore, we can etch a Cu surface conically in ultrapure water. The current efficiency increases by 70% at maximum, and the minimum current required for electrochemical etching decreases compared with that in the case of using an unmodified electrode.