SCANNING ELECTRON MICROSCOPE WITH MEANS TO REMOVE LOW ENERGY ELECTRONS FROM THE PRIMARY ELECTRON BEAM

摘要

In scanning electron microscopes, the beam of primary electrons generated by an electron gun contains low energy stray electrons as it passes through the condenser lens system on route to the specimen. The stray electrons adversely affect the secondary electron image. By incorporating a retarding electrode maintained at negative potential as described in this specification, the undesirable stray electrons are removed from the beam of primary electrons on the basis of the energy difference between the two groups of electrons.