Scanning Electron Diffraction Attachment with Electron Energy Filtering

Abstract

A scanning electron diffraction attachment providing for energy analysis of the scattered electrons has been constructed for use in conjunction with a J.E.M. 6AS electron microscope. This attachment permits the direct recording of diffracted electron intensities as a function of angle with an accuracy of ±0.1%. The attachment can be operated to exclude all but the elastically diffracted electrons, or, alternatively, to detect electrons with a measurable amount of energy loss. The electrostatic energy analyzer has an energy cutoff of better than 1.1 eV out of 100 keV. The angular resolution of the instrument is presently 2.2×10⁻⁴ rad, with minimum detectable electron intensity of 10⁻¹⁴ A. The instrument performance is demonstrated by studying the effect of inelastic scattering in the diffraction pattern of aluminum, and by recording the plasma loss spectrum of aluminum. The filtered profiles have narrower peaks than the unfiltered ones and better peak resolution, and the contrast between peaks and background is enhanced. At low values of the scattering vector where the inelastic background is very intense, its removal reveals diffraction effects which otherwise would have been invisible. The attachment does not interfere with the conventional plate microscopy and diffraction, and provides, thereby, a method of energy analyzing the direct microscope image as well.