Electron optical aspects of the dual-emission electron spectromicroscope

Abstract

The electron optical configuration of the novel dual-emission electronspectromicroscope (DEEM) is discussed. The idea of DEEM is based on theconcept of the double deflection of the electron beam, initially by the angle+α,through the first concentric spherical deflector and then, after passing through the relay lens, by theangle −α through the second concentric spherical deflector. That novel concept allows parallelobservation at two independent imaging units of two different electron optical images: theunfiltered real image and energy filtered electron angular distribution or electron angulardistribution and the energy filtered real image. The dispersion of the first deflector lenssystem is used for the selection of the energy range of the emitted electrons. The relay lensreverses the sign of the distance from the electron optical axis and the angle to thisaxis of the electron at the input to the second deflector, leading in the ideal case(Cc and Cs equal to 0) to the cancellation of the chromatic and spherical aberrations in the outputimage plane of the deflector system.It will be also shown that DEEM instrumentation allows high energy electron sampleillumination, which opens new possibilities for chemical mapping and analysis (ESCA,Auger) on a nanometric scale under laboratory conditions.