Monochromators and aberration correctors: Taking EELS to new levels of energy and spatial resolution

The development of monochromators and aberration correctors for transmission electron microscopes (TEM) has paved the way for a level of imaging and analysis that is unmatched by other methods. While current instrumentation does not permit the optimum spatial resolution of the microscope to be coupled with this high energy resolution, detailed spectroscopic analyses can be performed with similar to 1nm spatial resolution. Combined with similar to 0.1 eV energy resolution this is particularly useful for the analysis of the low-loss region of the spectrum, permitting quantum confinement effects and optical responses of individual nanostructures to be measured. Higher spatial resolution can be obtained from aberration corrected STEM, where spectral resolution of -0.4eV can be coupled with a spatial resolution of < 0.1 nm. Such resolution is particularly useful for analyzing core-loss signals at defects and interfaces, where localized. structural and compositional modulations are expected to have a large effect on the structure-property relationships. Results from aberration corrected and monochromated systems will be presented to highlight the application of EELS to the study of Si3N4, GaN and extraterrestrial particles.