Traditional scanning transmission electron microscopy (STEM) integrates the electron signal over a subset of scattering angle to form commonly used imaging modes. However, there is potentially much more information contained in the full two dimensional convergent beam electron diffraction (CBED) patterns. By using a fast direct detection camera, a Gatan K2-IS installed on a probe aberration corrected FEI Titan electron microscope, we acquired four dimensional diffraction patterns (4D-STEM) simultaneously with high-angle annular dark field STEM images from a SrTiO3 specimen using an atomic size convergent probe. Multiple imaging modes, such as bright field, annular bright field and annular dark field images can be synthesized from post-acquisition data analyses on these huge datasets. Position-averaged CBED can be used to investigate the thickness or defect properties of materials on a cell-by-cell basis. Moreover, approaches to phase reconstruction, such as differential phase contrast imaging and ptychography, will be explored and compared. Other possible uses for 4D-STEM datasets and method to handle and analyse these huge datasets (hundreds of GBs) will also be demonstrated [1].
[1]. The authors wish to thank Drs. Peter Ercius and Jim Ciston for the assistance during the experiments and acknowledge the support from the Australian Research Council’s Discovery Projects funding scheme (Projects DP110102228 and DP140102538) and DECRA funding scheme (Project DE130100739). Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, Office of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.