Nanoscale Electrochemistry

The lateral extension of electrochemically induced surface modifications is usually determined by the macroscopic size of the electrodes and the diffusion length of the reacting species. To overcome this constraint, we conducted an electrochemical reaction far from equilibrium. We applied short voltage pulses ( $\le 100\mathrm{ns}$, up to $\pm 4\mathrm{V}$) to a scanning tunneling microscope tip while imaging a Au(111) surface in concentrated electrolytes. They lead either to hole formation by anodic dissolution of the Au or to cathodic deposition of Cu islands (in the ${\mathrm{Cu}}^{2+}$ containing electrolyte), both of nanometer extension.