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Pofelski A, Whabi V, Ghanad-Tavakoli S, Botton G. Assessment of the strain depth sensitivity of Moiré sampling Scanning Transmission Electron Microscopy Geometrical Phase Analysis through a comparison with Dark-Field Electron Holography. Ultramicroscopy 2021; 223:113225. [PMID: 33592519 DOI: 10.1016/j.ultramic.2021.113225] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 01/25/2021] [Accepted: 02/07/2021] [Indexed: 11/16/2022]
Abstract
In this study, the Moiré sampling Scanning Transmission Electron Microscopy Geometrical Phase Analysis (or STEM Moiré GPA) strain characterization method is compared to the well-established Dark-Field Electron Holography technique on a thin film stack grown by Molecular Beam Epitaxy. While experimental data obtained with the two techniques are, overall, in good qualitative agreement, small statistically relevant differences are locally observed between the two methods. The results obtained from both techniques are further confronted with Finite Element Method (FEM) mechanical simulations modeling the strain relaxation phenomena from a thin lamella. The FEM simulation highlights a non-uniform deformation field along the beam propagation direction with a higher deformation level near the surface of the lamella compared to the center of the same lamella. The center-surface strain differences obtained from modeling are consistent with the experimentally derived differences accounting for the fact that the SMG method is sensitive to the strain state of the surface of the lamella with a very narrow depth-of-field, and the DFEH technique is measuring the strain state of the center of the same lamella averaging over a large section of the thickness. The depth-of-field difference between both methods can be reasonably related to their respective contrast mechanisms (STEM vs Conventional Transmission Electron Microscopy). As the SMG method is using a convergent probe, the narrow depth-of-field might be used to sense the deformation field over different sections of the lamella using the defocus and potentially retrieve the three-dimensional strain field.
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Affiliation(s)
- A Pofelski
- Department of Materials Science and Engineering, McMaster University, Hamilton, Canada.
| | - V Whabi
- Department of Materials Science and Engineering, McMaster University, Hamilton, Canada
| | - S Ghanad-Tavakoli
- Department of Engineering Physics and Centre for Emerging Devices Technology, McMaster University, Hamilton, Canada
| | - G Botton
- Department of Materials Science and Engineering, McMaster University, Hamilton, Canada.
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Xu R, Chen CC, Wu L, Scott MC, Theis W, Ophus C, Bartels M, Yang Y, Ramezani-Dakhel H, Sawaya MR, Heinz H, Marks LD, Ercius P, Miao J. Three-dimensional coordinates of individual atoms in materials revealed by electron tomography. NATURE MATERIALS 2015; 14:1099-103. [PMID: 26390325 DOI: 10.1038/nmat4426] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 08/17/2015] [Indexed: 05/22/2023]
Abstract
Crystallography, the primary method for determining the 3D atomic positions in crystals, has been fundamental to the development of many fields of science. However, the atomic positions obtained from crystallography represent a global average of many unit cells in a crystal. Here, we report, for the first time, the determination of the 3D coordinates of thousands of individual atoms and a point defect in a material by electron tomography with a precision of ∼19 pm, where the crystallinity of the material is not assumed. From the coordinates of these individual atoms, we measure the atomic displacement field and the full strain tensor with a 3D resolution of ∼1 nm(3) and a precision of ∼10(-3), which are further verified by density functional theory calculations and molecular dynamics simulations. The ability to precisely localize the 3D coordinates of individual atoms in materials without assuming crystallinity is expected to find important applications in materials science, nanoscience, physics, chemistry and biology.
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Affiliation(s)
- Rui Xu
- Department of Physics &Astronomy and California NanoSystems Institute, University of California, Los Angeles, California 90095, USA
| | - Chien-Chun Chen
- Department of Physics &Astronomy and California NanoSystems Institute, University of California, Los Angeles, California 90095, USA
- Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan
| | - Li Wu
- Department of Physics &Astronomy and California NanoSystems Institute, University of California, Los Angeles, California 90095, USA
| | - M C Scott
- Department of Physics &Astronomy and California NanoSystems Institute, University of California, Los Angeles, California 90095, USA
| | - W Theis
- Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Colin Ophus
- National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Matthias Bartels
- Department of Physics &Astronomy and California NanoSystems Institute, University of California, Los Angeles, California 90095, USA
| | - Yongsoo Yang
- Department of Physics &Astronomy and California NanoSystems Institute, University of California, Los Angeles, California 90095, USA
| | | | - Michael R Sawaya
- Howard Hughes Medical Institute, UCLA-DOE Institute of Genomics and Proteomics, Los Angeles, California 90095-1570, USA
| | - Hendrik Heinz
- Department of Polymer Engineering, University of Akron, Akron, Ohio 44325, USA
| | - Laurence D Marks
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60201, USA
| | - Peter Ercius
- National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Jianwei Miao
- Department of Physics &Astronomy and California NanoSystems Institute, University of California, Los Angeles, California 90095, USA
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