In-situ atomic force microscopy (AFM) is shown to locally enhance the electrochemical deposition of copper (Cu) onto single-crystal Cu surfaces. The tip-sample interaction increases the growth rate of Cu, resulting in the localized formation of nanometer scale epitaxial deposits. The results are consistent with a heterogeneous nucleation and growth mechanism in which the tip-sample interaction creates surface defect sites in a passivating layer which are active toward the electrochemical adsorption of Cu species. This protection-deprotection scheme enables precise control of feature sizes and allows this technique to be used for fabrication and constructive modification of solid-liquid interfaces.