This work presents observations of symmetry breakages in the intensity distributions of near-zone-axis convergent-beam electron diffraction (CBED) patterns that can only be explained by the symmetry of the specimen and not the symmetry of the unit cell describing the atomic structure of the material. The specimen is an aluminium-copper-tin alloy containing voids many tens of nanometres in size within continuous single crystals of the aluminium host matrix. Several CBED patterns where the incident beam enters and exits parallel void facets without the incident beam being perpendicular to these facets are examined. The symmetries in their intensity distributions are explained by the specimen morphology alone using a geometric argument based on the multislice theory. This work shows that it is possible to deduce nanoscale morphological information about the specimen in the direction of the electron beam - the elusive third dimension in transmission electron microscopy - from the inspection of CBED patterns.
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http://dx.doi.org/10.1107/S1600576724001614 | DOI Listing |
Sci Rep
July 2024
School of Electrical and Computer Engineering, University of Oklahoma, Norman, OK, 73019, USA.
Spontaneous polarization and crystallographic orientations within ferroelectric domains are investigated using an epitaxially grown BiFeO thin film under bi-axial tensile strain. Four dimensional-scanning transmission electron microscopy (4D-STEM) and atomic resolution STEM techniques revealed that the tensile strain applied is not enough to cause breakdown of equilibrium BiFeO symmetry (rhombohedral with space group: R3c). 4D-STEM data exhibit two types of BiFeO ferroelectric domains: one with projected polarization vector possessing out-of-plane component only, and the other with that consisting of both in-plane and out-of-plane components.
View Article and Find Full Text PDFJ Microsc
September 2024
Department of Mechanical, Materials and Aerospace Engineering, University of Liverpool, Liverpool, UK.
Here we show that compressive sensing allows 4-dimensional (4-D) STEM data to be obtained and accurately reconstructed with both high-speed and reduced electron fluence. The methodology needed to achieve these results compared to conventional 4-D approaches requires only that a random subset of probe locations is acquired from the typical regular scanning grid, which immediately generates both higher speed and the lower fluence experimentally. We also consider downsampling of the detector, showing that oversampling is inherent within convergent beam electron diffraction (CBED) patterns and that detector downsampling does not reduce precision but allows faster experimental data acquisition.
View Article and Find Full Text PDFJ Appl Crystallogr
April 2024
Department of Materials Science and Engineering, Monash University, Victoria 3800, Australia.
This work presents observations of symmetry breakages in the intensity distributions of near-zone-axis convergent-beam electron diffraction (CBED) patterns that can only be explained by the symmetry of the specimen and not the symmetry of the unit cell describing the atomic structure of the material. The specimen is an aluminium-copper-tin alloy containing voids many tens of nanometres in size within continuous single crystals of the aluminium host matrix. Several CBED patterns where the incident beam enters and exits parallel void facets without the incident beam being perpendicular to these facets are examined.
View Article and Find Full Text PDFMicroscopy (Oxf)
December 2022
Advanced Research Laboratory, Saitama Institute of Technology, Fusaiji 1690, Fukaya, Saitama 369-0293, Japan.
Recent advances in the production of electron vortex beams carrying orbital angular momentum (OAM) offer unique opportunities to explore materials at the nanoscale level. We present a novel method for observing convergent-beam electron diffraction (CBED) patterns by using an electron vortex beam. In a transmission electron microscope, a series of electron vortex beams generated by a forked grating mask located above the specimen illuminate the specimen, and CBED patterns are imaged onto the observation plane of the microscope, selecting one of the electron vortex beams using an aperture located beneath the specimen.
View Article and Find Full Text PDFJ Microsc
October 2022
School of Materials, University of Manchester, Manchester, UK.
Convergent beam electron diffraction (CBED) was used to profile the thickness of aluminium alloys foils prepared by using the twinjet electropolishing method. The two-beam CBED condition was obtained by exciting the and aluminium diffracted g-vector. The aluminium alloy foil thicknesses were calculated at different distances from the sample hole edge.
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