Fabrication of metallic nano-protrusion for a recording mark

We fabricated nano-protrusions on metallic multilayers by nano-oxidation with atomic force microscope (AFM). Two types of multilayers, namely Ti/Au/Ti and Ti/Ag/Ti were prepared, where the thickness of each layer was below ∼10 nm. For the fabricated samples, we obtained near-field scanning optical microscope (NSOM) images. With the NSOM image, we examined the light-intensity ratio of nano-protrusion to background and found that the light-intensity ratio was increased only in the Ti/Au/Ti sample. This result might be attributed to the resonant coupling of surface plasmon (SP) to the incident light from the NSOM tip, which was consistent with the results of transmittance spectra.