Real time computer simulation of transmission electron microscope images with tilted illumination: grain boundary applications.

Computer programs have been developed to simulate electron microscope images from digitized graphically represented model structures. Via a television rate image processing system, these programs allow real time, interactive modification of the microscope objective lens parameters, incident beam inclination, and incident beam energy. In addition to explaining the computational methods, the need for using tilted beam illumination is explored to extend microscope resolution. For this study, the subject of grain boundary imaging is analyzed for a copper sigma = 5, 36.9 degrees, (310) tilt boundary with a [001] common rotation axis. The Cu [200] lattice spacings of approximately 1.8A on both sides of the interface cannot be reliably resolved under axial illumination conditions in a 200 kV microscope. Therefore, either tilted beam modes or higher incident beam energies were explored and the types of image features correlated with atomic position data through the digital frame store system.