title: Diffraction contrast imaging using virtual apertures.
abstract: Two methods on how to obtain the full diffraction information from a sample region and the associated reconstruction of images or diffraction patterns using virtual apertures are demonstrated. In a STEM-based approach, diffraction patterns are recorded for each beam position using a small probe convergence angle. Similarly, a tilt series of TEM dark-field images is acquired. The resulting datasets allow the reconstruction of either electron diffraction patterns, or bright-, dark- or annular dark-field images using virtual apertures. The experimental procedures of both methods are presented in the paper and are applied to a precipitation strengthened and creep deformed ferritic alloy with a complex microstructure. The reconstructed virtual images are compared with conventional TEM images. The major advantage is that arbitrarily shaped virtual apertures generated with image processing software can be designed without facing any physical limitations. In addition, any virtual detector that is specifically designed according to the underlying crystal structure can be created to optimize image contrast.
authors.affiliation: National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, United States; Department of Materials Science and Engineering, University of California, Berkeley, United States; Physics of Nanostructured Materials, Faculty of Physics, University of Vienna, Austria. Electronic address: cgammer@lbl.gov.
authors.forename: Christoph
authors.initials: C
authors.lastname: Gammer
authors.affiliation: National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, United States.
authors.forename: V
authors.initials: V
authors.lastname: Burak Ozdol
authors.affiliation: National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, United States; Department of Materials Science and Engineering, University of California, Berkeley, United States.
authors.forename: Christian H
authors.initials: CH
authors.lastname: Liebscher
authors.affiliation: National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, United States; Department of Materials Science and Engineering, University of California, Berkeley, United States.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Minor
keywords: Dark field scanning; Diffraction imaging; Large data; Nanodiffraction; Precipitates; Virtual microscopy