LAUSR

Electron energy loss spectroscopy (EELS) in a transmission electron microscope (TEM) is a valuable tool for characterizing the fundamental chemical, photonic, and vibrational behavior of materials with high spatial resolution. When performing traditional EELS, one integrates all momenta (q) entering the entrance aperture into a single energy loss spectrum (ELS). Consequently, the collected data lack information that the dispersive nature of the phenomena may provide. For example, one can extract information about the local electron density (n) from the ELS due to a plasmon excitation, but one can additionally determine the extent of interaction between individual electrons in the plasma, as well as the Fermi energy by characterizing its dispersion, i.e., using its q dependence [1]. A TEM can be outfitted with a specially designed q-slit aperture, which allows selection of specific directions in q-space to enter the EELS, but such q-slits are not a typical installation. Hence, we devised a technique to obtain the qdependence of plasmon excitations at grain boundaries (GBs) with high spatial resolution, using a FEI Titan TEM at 300 kV with a Tridiem Model 863P Gatan imaging filter without a q-slit.