SPATIAL-RESOLUTION IN SELECTED-AREA EELS

We investigate the effect of objective-lens chromatic aberration on qu antitative chemical microanalysis using electron energy-loss spectrome try in the electron microscope. Experimental tests were done on a spec imen with a planar interface under the condition of a rather large chr omatic 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 desc ribes the experimental data satisfactorily. A method to obtain a prope r defocus setting for the compensation of the chromatic error is also presented.