Description
Metallic surfaces can support charge density waves, quasi-particles known as surface plasmon polaritons (SPPs). When the physical extent of the metal is in the nanoscale regime, i.e., < 100 nm, the SPPs are physically confined and nanoparticle supports collective oscillations known as localized surface plasmon resonances (LSPRs). Such nanostructures can localize and manipulate electromagnetic fields in dimensions smaller than the optical diffraction limit. Studying these subwavelength phenomena is challenging because optical characterization methods do not provide a broad wavelength excitation source and cannot spatially resolve subwavelength plasmonic modes.
Cathodoluminescence (CL) in the scanning electron microscope (SEM) or scanning/transmission electron microscope (S/TEM) is a powerful tool for characterizing the properties of metallic nanoparticles at their true length scale. Here the fast electrons act as broad wavelength, localized nanoscale excitation source. The emitted CL probes the radiative component of the optical or electromagnetic local density of states (LDOS) projected along the electron beam direction. CL spectroscopy gives insight into many aspects of the emitted light with nanoscale spatial resolution, for example, position, direction, wavelength and polarization.
In this work, we use CL in the SEM to characterize chemically-synthesized gold nanotriangles with varying size from 100 nm to a few micrometres in diameter and 80 nm thickness on SiN substrate. We performed spectrally resolved CL mapping using a Delmic SPARC CL system on a Nova Nanosem 450 (30 keV, 1.2 nA). Using spectral decomposition, we found the nature of LSPRs in gold nanotriangles are highly size-dependent. The current work demonstrates CL spectroscopy can excite LSPRs with high spatial resolution for complete characterization of individual plasmonic nanostructures to engineer them for light harvesting and sensing applications.
[1] A. C. Y. Liu et al, Small 2023, 19, 2207747.
[2] A. D. Mayevsky… A. M. Funston et al, Optics Express 2018, 26, 23426-23435.
| I am the presenting author | Yes |
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