Abstract
Using high-resolution electron-beam lithography and lift-off, Au structures with sub-10 nm dimensions or spacings were fabricated on 30-nm-thick silicon-nitride (SiN) membranes. Fabricating metal nanostructures on electron-transparent SiN membranes permitted their surface plasmon resonances to be measured using electron energy-loss spectroscopy in a scanning transmission electron microscope (STEM). The surface plasmons that were excited by the 300 keV electron beam exhibited spatially and spectrally distinct longitudinal and transverse modes in elongated Au nanostructures. As the plasmonic response of the nanoparticle was dependent on the point of excitation of the STEM beam, a surface plasmon map could be obtained with nanometer resolution for nanostructures with various geometries. This combination of high-resolution lithography and microscopy will facilitate the design and systematic study of plasmonic nanostructures.