IMAGING OF DISLOCATIONS USING BACKSCATTERED ELECTRONS IN A SCANNING ELECTRON-MICROSCOPE

A field-emission-gun scanning electron microscope (FEG SEM) has been fitted with a back-scattered electron detector in order to image dislocations by the electron channelling contrast mechanism. By using an efficient detector, optimizing its orientation with respect to the specimen and the incident beam, and applying an image-enhancement technique, it has been possible to image and characterize dislocations near the surface of bulk samples of a number of materials without the need of an electron-energy filter in front of the detector. Examples are presented of preliminary studies of dislocations in Si and Ni3Ga; the image widths are typically 20 nm, and the normal g • b=0 invisibility criterion for screw dislocations applies. By dispensing with the electron-energy filter used by Morin et al., the design and operation of the system become very simple, and the technique should become available in commercial FEG SEMs. This non-destructive technique is likely to have wide applications to situations where conventional ‘thin-film’ microscopy is impractical or undesirable. © 1990 Taylor & Francis Group, LLC.