Multichannel detection high-resolution electron energy loss spectrometer

Abstract

A new general-purpose high-resolution electron energy loss spectrometer has been constructed and tested. Novel features of the electron optics include multichannel energy detection and tandem four-element zoom lenses that incorporate beam defining apertures. Compact design of the lenses permit scattering measurements in which the total scattering angle is less than 40°. This feature permits probing bulk phonon modes. The lens system permits electronic adjustment of the analyzer collection angle, and yields high transmission at retardation/acceleration ratios of 400:1. Performance characteristics include simultaneous detection of 50 energy channels at 4-meV energy resolution and target currents exceeding 2×10−10 A. Separate monochromator and analyzer goniometers permit access to out-of-plane scattering configurations which enables probing odd symmetry shear surface modes.