SPATIAL-RESOLUTION IN SELECTED-AREA EELS

We investigate the effect of objective-lens chromatic aberration on quantitative chemical microanalysis using electron energy-loss spectrometry in the electron microscope. Experimental tests were done on a specimen with a planar interface under the condition of a rather large chromatic error in image mode. We discuss three different models of image formation with inelastically scattered electrons. Simulations for Ni show that the quantum-mechanical image theory for large defocus values is practically equivalent to a Lorentzian image distribution and describes the experimental data satisfactorily. A method to obtain a proper defocus setting for the compensation of the chromatic error is also presented.