Mechanism of Prism-Coupled Scanning Tunneling Microscope Light Emission

Abstract

We have investigated the mechanism of scanning tunneling microscope light emission (STM-LE) in a prism-coupled configuration using finite difference time domain analysis. In this configuration, the sample is a metallic thin film evaporated on the bottom surface of a hemispherical glass prism. STM light emitted into the prism (prism-side emission) through the metallic film is measured. Since both localized surface plasmons (LSP) and surface plasmon polaritons (SPP) contribute to prism-side emission, this emission is stronger than that in conventional STM-LE measured from the sample surface side, which is radiated by LSP alone. We show that the spatial resolution of prism-side emission is determined not by the propagation length of SPP, but by the lateral size of LSP, similarly to conventional (i.e., tip side) STM-LE. Thus, we conclude that, by using the prism-coupled configuration, the signal level of STM-LE improves without the loss of spatial resolution attained in tip side emission.

Photoluminescence of a Plasmonic Molecule

“…3,8,11,13,21 Direct surface plasmon emission has also been proposed to be feasible and theoretically verified for the visible light emission from a scanning tunneling microscope probing silver films. 41,42 While a small blue shift between PL and DFS spectra was previously noted for Au nanorods, 8,9 it was mainly ignored as it could not be easily explained. However, the differences observed here in the PL and DFS spectra for the AuNS monomers and dimers (Figure 3) are much more significant, as already mentioned above.…”

Creation and Luminescence of a Single Silver Nanoparticle on Si(111) Investigated by Scanning Tunneling Microscopy

“…This is similarly seen in the previous result, i.e., the calculation of the STM-LE from the Au substrate with the W tip. 51,52,57 The tip size dependence observed in the radiation intensity is ascribed to the periphery effect; i.e., the part of light emitted from the tip−sample gap is blocked due to the presence of the STM tip. One can expect that the radiation intensity should be reduced with the tip radius above the certain critical value.…”