The benefits of energy-filtering in weak-beam microscopy

We have explored systematically the benefits of energy filtering to remove inelastically-scattered electrons with energy losses greater than about 10 eV from weak-beam images of dislocations. Digital weak-beam images were obtained of long dislocations in Ni3Ga using a Gatan Imaging Filter attached to a Jeol 3000F FEGTEM. The image quality was assessed in terms of three parameters: the image peak width; the peak-to-background ratio; and the signal-to-noise ratio. All three of these measures were significantly improved in "zero-loss" energy-filtered images compared with unfiltered images taken under the same imaging conditions particularly in thick areas of foil (> 100 nm), where unfiltered images were badly degraded by chromatic aberration. In a foil of thickness similar to180nm energy-filtered images were of comparable quality to those obtainable in thin areas of foil (< 50 nm).