Detection of ion implantation in focused ion beam processing by scattering-type scanning near-field optical...

We employed scattering-type scanning near-field optical microscopy (s-SNOM) to explore the implantation of gallium ions in a silicon substrate after focused ion beam (FIB) etching. Different ion doses were applied, and the s-SNOM amplitude image contrast between the processed and unprocessed regions was investigated. The results demonstrate that the contrast decreases along with the increase of the ion dose. A similar dependence of the residual gallium element concentration on the ion dose is found from the energy dispersive spectroscopy. Such comparisons imply that s-SNOM imaging is sensitive to the implanted ions. The s-SNOM aided analysis of FIB etching can benefit the fabrication optimization, especially when the processed materials' properties are of critical importance.