  Focused electron beam induced deposition of pure materials from aqueous
solutions has been of interest in recent years. However, controlling the liquid
film in partial vacuum is challenging. Here we modify the substrate to increase
control over the liquid layer in order to conduct a parametric study of copper
deposition in an environmental SEM. We identified the transition from electron
to mass-transport limited deposition as well as two additional regimes
characterized by aggregated and high-aspect ratio deposits. We observe a high
deposition efficiency of 1 to 10 copper atoms per primary electron that is
consistent with a radiation chemical model of the deposition process.
