Energy-filtered convergent-beam diffraction: examples and future prospects

The addition of an imaging filter to a cold field-emission TEM has led to the development of new techniques based on the analysis of the zero-loss or a specific energy-loss signal. For example, the removal of inelastically scattered electrons can improve the fringe contrast in coherent CBED patterns from relatively thick crystals. Similarly, this energy-filtering is essential for the accurate measurement of low-order structure factors by CBED pattern matching. Studies of convergent-beam patterns recorded at specific core-loss energies show that they contain chemically sensitive features. In addition, hybrid modes of operation have been developed that allow spectrum-images and spectrum-diffraction patterns to be obtained. New results are presented that show the use of these techniques. Finally, it is argued that energy-filtering should lead to improvements in critical-voltage measurements, latticeparameter determination and in the resolution of branch cluster information.