STM tip induced local etching and deposition on Cu surfaces

At cathodic potential of bulk copper deposition in dilute Cu 2+ solution, tip was found to be able to induce local dissolution of copper by applying a rather positive tip potential, although meanwhile the copper was still deposited on the surface far from the tip area. The more positive the tip potential or the electrode potential is, the faster induced dissolution rate is. At a rather negative tip potential, deposition of Cu was enhanced by the tip while in the case Cu was dissolved locally with a more positive tip potential. A mechanism based on overlap of double layers between tip and substrate was proposed.