The influence of the degree of the deviation from the bragg condition on the visibility of dislocations in copper

Abstract

Dislocations in copper have been imaged under various two-beam diffracting conditions using transmission electron microscopy and it has been shown that very weak images are generally associated with diffracting vectors as large or larger than 311 for those dislocations for which g . b = 1, where g is the diffracting vector and b the Burgers vector of the dislocation. Computed images confirm that this weak contrast is associated with the large value of s, the deviation parameter, which is selected experimentally with such diffracting vectors, Care is therefore necessary if large diffracting vectors are used in determining the Burgers vectors of dislocations, or the density of dislocations.