High-voltage transmission scanning electron microscopy

The use of scanning electron microscopy for the study of thin specimens by transmission has advantages over conventional transmission electron microscopy in terms of simplicity and cheapness, reduction in damage to irradiation-sensitive specimens and convenience for electron diffraction, energy analysis and the electronic measurement and recording of images. These advantages are specially important for microscopes operating in the range 200 kV to 1 MeV. The design of a 600 kV instrument to exploit these advantages is described. The possible modes of operation employing deflexion systems and an energy analyser are discussed with reference to light- and dark-field microscopy, convergent beam diffraction and conventional focused diffraction patterns. The reciprocity principle is invoked to relate both image contrast and instrument design in scanning electron microscopy to that in conventional transmission electron microscopy. Examples are given of light- and dark-field images and diffraction patterns obtained with the instrument.