Symmetry quantification and mapping using convergent beam electron diffraction

We propose a new algorithm to quantify symmetry recorded in convergent beam electron diffraction (CBED) patterns and use it for symmetry mapping in materials applications. We evaluate the effectiveness of the profile R-factor (R-p) and the normalized cross-correlation coefficient (gamma) for quantifying the amount of symmetry in a CBED pattern. The symmetry quantification procedures are automated and the algorithm is implemented as a DM (Digital Micrograph (c)) script. Experimental and simulated CBED patterns recorded from a Si single crystal are used to calibrate the proposed algorithm for the symmetry quantification. The proposed algorithm is then applied to a Si sample with defects to test the sensitivity of symmetry quantification to defects. Using the mirror symmetry as an example, we demonstrate that the normalized cross-correlation coefficient provides an effective and robust measurement of the symmetry recorded in experimental CBED patterns. (C) 2012 Elsevier B.V. All rights reserved.