Analysis of carbon content in direct-write plasmonic Au structures by nanomechanical scanning absorption microscopy

In this work, a novel chemical composition characterization method of direct-write focused electron beam-induced deposition (FEBID) gold nanostructures is presented. The reliable determination of the chemical content for nanostructures has been challenging due to its limited interaction volume. We hereby propose an alternative technique for measuring the chemical composition of nanostructures with limited volume. By measuring the differences in the optical absorption of the nanostructure due to the differences in the chemical composition with the resonance frequency detuning of a nanomechanical resonator and the assistance of analytical optical modeling, we demonstrate the possibility of characterizing the carbon content in the (FEBID) gold nanostructures. From our characterization method, the post-purification process with water successfully reduced the carbon content from ∼65 at. % to ∼20 at. %. This method presents a new technique for the chemical analysis of nanostructures.