Electron microscopy probing electron-photon interactions in SiC nanowires with ultra-wide energy and momentum match

TL;DR

This study employs advanced STEM-EELS to probe electron-photon interactions in SiC nanowires, revealing resonant modes and size effects at nanoscale resolution, offering a new method for optical spectroscopy of nanostructures.

Contribution

It introduces a novel application of STEM-EELS with ultra-wide energy and momentum match to study optical resonances in single nanowires, surpassing traditional optical spectroscopy limitations.

Findings

Simultaneous excitation of Fabry-Perot and whispering-gallery modes across a broad spectrum.

Revealed size-dependent effects on nanowire resonant spectra.

Measured nanoscale decay length of resonant electron energy loss spectroscopy.

Abstract

Nanoscale materials usually can trap light and strongly interact with it leading to many photonic device applications. The light-matter interactions are commonly probed by optical spectroscopy, which, however, have some limitations such as diffraction-limited spatial resolution, tiny momentum transfer and non-continuous excitation/detection. In this work, using scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) with ultra-wide energy and momentum match and sub-nanometer spatial resolution, we study the optical microcavity resonant spectroscopy in a single SiC nanowire. The longitudinal Fabry-Perot (FP) resonating modes and the transverse whispering-gallery modes (WGMs) are simultaneously excited and detected, which span from near-infrared (~ 1.2 {\mu}m) to ultraviolet (~ 0.2 {\mu}m) spectral regime and the momentum transfer can be ranging up to 108 cm{^{-1}}. The size effects on the resonant spectra of nanowires are also revealed. Moreover, the nanoscale decay length of resonant EELS is revealed, which is contributed by the strongly localized electron-photon interactions in the SiC nanowire. This work provides a new alternative technique to investigate the optical resonating spectroscopy of a single nanowire structure and to explore the light-matter interactions in dielectric nanostructures, which is also promising for modulating free electrons via photonic structures.