Convergent beam diffraction studies of interfaces, defects, and multilayers

Abstract

This paper explains how the convergent beam electron diffraction (CBED) and large angle convergent beam (LACBED) techniques can be used to study crystal defects, bicrystals, and multilayers. It is shown how the LACBED technique in particular can be used to derive the magnitude and sign of the Burgers vectors of dislocations and displacements at stacking faults. For bicrystals and multilayers examined in plan-view, LACBED gives the rocking curve for a chosen reflection. This enables layer strains to be measured to approximately 0.1% and composition profiles derived for both periodic and aperiodic structures. It is shown that a simple kinematic approach can be used to interpret the essential results in most cases.

Open core threading dislocations in GaN grown by hydride vapour phase epitaxy

“…However, Northrup [9] has suggested that the surface energy could be lowered, and the equilibrium radius increased, by the presence of impurities on the {10-10} nanopipe surfaces during In this bright field image, the g = 0004 contour is seen to deviate and split on crossing a nanopipe. This splitting has been analysed in LACBED studies of dislocations [12], but applies equally well in images where the specimen is bent, as in Figure In all cases, the background was removed by using a power law fit to the pre-edge curve, and the remaining counts integrated over an extended energy window extending at least 20eV from the onset of the edge. In order to compare the curves, the Ga and N signals have been scaled to be in the ratio 1:1 far from the nanopipes, and the O signal has then been scaled to the N signal by using the relative K-shell cross-sections [13].…”

Application of the Convergent Beam Imaging (CBIM) Technique to the Analysis of Crystal Defects

“…Cherns and Preston have shown that this mapping can be very useful for the analysis of dislocations since it gives typical effects directly connected with the Burgers vector of the dislocations [2]. Burgers vectors were first determined from CBED patterns by Carpenter and Spence [3], who described methods for computing these patterns in two and n-beam theory.…”

CBED strain measurements in boron implanted silicon

“…The methods of CBED strain measurements have been extensively reviewed by Humphreys et aL [12] and Cherns and Preston [13] and their application to the detection and measurements of the tetragonal strain will only be summarized here.…”