Control of surface charge for high‐fidelity nanostructuring of materials

The universal problem of surface charging during focused ion milling has been fully resolved using a flood‐gun approach based on simultaneous co‐illumination with a UV light‐emitting diode (LED). Non‐distorted as‐designed nano‐patterns were milled using Ga + ions on dielectric materials which charge up strongly. Deep‐UV (250–280 nm) LED co‐illumination during the ion beam milling fully discharges optically the surface under standard Ga + ion‐milling conditions. Photo‐ionization of electrons trapped at the sub‐surface defects to the free vacuum state is a key to the phenomenon ( nm corresponds to a photon energy eV). The method is applicable as a solution to other charging problems where electrons (primary or secondary) and their spatial redistribution affect nanofabrication or imaging.