Effects of dislocation loop morphology in titanium on diffraction contrast

To identify the origin of a fringe contrast, the authors performed studies using computer-simulated electron-microscope images. These simulated images were calculated using the scattering matrix method for an imperfect crystal and the expressions of Ohr for the displacements around a finite mixed circular loop in an isotropic medium. To simulate the contrast in the images, care was taken to reproduce the experimental conditions accurately. A foil thickness of 200 nm with the loops located at the middle was assumed and six systematic reflections were included in the calculations to satisfy the weak-beam imaging conditions. Results of the calculations are shown, and an alternative explanation for the fringe contrast was found in the elliptical shape of the experimental loops. 4 references, 3 figures