Pushing the limits of energy resolution by combining monochromated EELS with the CEOS energy-filtering and imaging device in the JEOL atomic-resolution multi-dimensional TEM.

We report the establishment of a platform for high-precision, meV-scale electron energy-loss spectroscopy (EELS) by the installation of the JEOL Atomic-Resolution Multi-Dimensional Transmission Electron Microscope (ARMD-TEM), which combines the CEOS Energy-Filtering and Imaging Device (CEFID) with a Wien-filter monochromator and aberration corrected optics, thus enabling ultra-stable, high-throughput low-loss spectroscopy with atomic-scale spatial resolution. Energy resolution and spectral stability are quantitatively assessed using zero-loss peak (ZLP) series of 10,000 spectra per dataset with sub-millisecond acquisition times and sub-channel energy-drift correction. Inherent energy resolutions below 20 meV with excellent temporal stability and reproducibility are demonstrated with the present Schottky field-emission source. Fourier analysis of ZLP drift identifies dominant frequencies contributing to spectral broadening and confirms effective suppression of environmentally induced instabilities. System performance is further validated by resolving plasmonic modes of aluminum nanoantennas and acoustic and optical phonon modes in hexagonal boron nitride, demonstrating reliable access to low-energy excitations in the 100 meV regime. These results demonstrate the potential of the ARMD-TEM-CEFID microscope, providing a foundation for future sub-20 meV resolved spectroscopy and multidimensional investigations of phonons, magnons, excitons, and other low-energy quasiparticles in solid materials.