Advances in crystal orientation mapping with the SEM and TEM

Abstract

Crystal lattice orientations are determined with high spatial resolution and accuracy in a fully automated process from backscatter or transmission Kikuchi patterns. The patterns are recorded with a low-light CCD camera from a fluorescence screen in the SEM specimen chamber or in the TEM projection chamber, respectively. Automated calibration procedures and software-controlled autofocusing have been developed for convenient and unattended orientation measurement with the SEM. Digital beam scan is used for automated crystal lattice orientation mapping (ACOM). In addition to Kikuchi patterns, spot diffraction patterns can be measured interactively in the TEM. On-line determination of Burgers vectors and deformation systems is facilitated in the TEM by simulating diffraction patterns on the computer as a function of sample tilt. Twinning systems are identified by considering the misorientation between twin and matrix, and indexing the twin boundary normals.