1
|
Anada S, Nomura Y, Yamamoto K. Enhancing performance of electron holography with mathematical and machine learning-based denoising techniques. Microscopy (Oxf) 2023; 72:461-484. [PMID: 37428597 DOI: 10.1093/jmicro/dfad037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 06/13/2023] [Accepted: 07/09/2023] [Indexed: 07/12/2023] Open
Abstract
Electron holography is a useful tool for analyzing functional properties, such as electromagnetic fields and strains of materials and devices. The performance of electron holography is limited by the 'shot noise' inherent in electron micrographs (holograms), which are composed of a finite number of electrons. A promising approach for addressing this issue is to use mathematical and machine learning-based image-processing techniques for hologram denoising. With the advancement of information science, denoising methods have become capable of extracting signals that are completely buried in noise, and they are being applied to electron microscopy, including electron holography. However, these advanced denoising methods are complex and have many parameters to be tuned; therefore, it is necessary to understand their principles in depth and use them carefully. Herein, we present an overview of the principles and usage of sparse coding, the wavelet hidden Markov model and tensor decomposition, which have been applied to electron holography. We also present evaluation results for the denoising performance of these methods obtained through their application to simulated and experimentally recorded holograms. Our analysis, review and comparison of the methods clarify the impact of denoising on electron holography research.
Collapse
Affiliation(s)
- Satoshi Anada
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587, Japan
| | - Yuki Nomura
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587, Japan
| | - Kazuo Yamamoto
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya, Aichi 456-8587, Japan
| |
Collapse
|
2
|
Lindner J, Ross U, Meyer T, Boureau V, Seibt M, Jooss C. Reconstruction of Angstrom resolution exit-waves by the application of drift-corrected phase-shifting off-axis electron holography. Ultramicroscopy 2023; 256:113880. [PMID: 37952372 DOI: 10.1016/j.ultramic.2023.113880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 10/05/2023] [Accepted: 10/21/2023] [Indexed: 11/14/2023]
Abstract
Phase-shifting electron holography is an excellent method to reveal electron wave phase information with very high phase sensitivity over a large range of spatial frequencies. It circumvents the limiting trade-off between fringe spacing and visibility of standard off-axis holography. Previous implementations have been limited by the independent drift of biprism and sample. We demonstrate here an advanced drift correction scheme for the hologram series that exploits the presence of an interface of the TEM specimen to the vacuum area in the hologram. It allows to obtain reliable phase information up to 2π/452 at the 1 Å information limit of the Titan 80-300 kV environmental transmission electron microscope used, by applying a moderate voltage of 250 V to a single biprism for a fringe spacing of 1 Å. The obtained phase and amplitude information is validated at a thin Pt sample by use of multislice image simulation with the frozen lattice approximation and shows excellent agreement. The presented method is applicable in any TEM equipped with at least one electron biprism and thus enables achieving high resolution off-axis holography in various instruments including those for in-situ applications. A software implementation for the acquisition, calibration and reconstruction is provided.
Collapse
Affiliation(s)
- J Lindner
- Institute of Materials Physics, University of Goettingen, Friedrich-Hund-Platz 1, 37077, Goettingen, Germany
| | - U Ross
- 4th Institute of Physics - Solids and Nanostructures, University of Goettingen, Friedrich-Hund-Platz 1, 37077, Goettingen, Germany
| | - T Meyer
- Institute of Materials Physics, University of Goettingen, Friedrich-Hund-Platz 1, 37077, Goettingen, Germany
| | - V Boureau
- Interdisciplinary Center for Electron Microscopy, École Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland
| | - M Seibt
- 4th Institute of Physics - Solids and Nanostructures, University of Goettingen, Friedrich-Hund-Platz 1, 37077, Goettingen, Germany
| | - Ch Jooss
- Institute of Materials Physics, University of Goettingen, Friedrich-Hund-Platz 1, 37077, Goettingen, Germany; International Center for Advanced Studies of Energy Conversion (ICASEC), University of Goettingen, D-37077, Goettingen, Germany.
| |
Collapse
|
3
|
Hÿtch M, Gatel C. Phase detection limits in off-axis electron holography from pixelated detectors: gain variations, geometric distortion and failure of reference-hologram correction. Microscopy (Oxf) 2021; 70:47-58. [PMID: 32744626 DOI: 10.1093/jmicro/dfaa044] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 07/15/2020] [Accepted: 07/27/2020] [Indexed: 11/13/2022] Open
Abstract
We investigate the effect that recording off-axis electron holograms on pixelated detectors, such as charge-coupled devices (CCD) and direct-detection devices (DDD), can have on measured amplitudes and phases. Theory will be developed for the case of perfectly uniform interference fringes illuminating an imperfect detector with gain variations and pixel displacements. We will show that both these types of defect produce a systematic noise in the phase images that depends on the position of the holographic fringes with respect to the detector. Subtracting a reference hologram from the object hologram will therefore not remove the phase noise if the initial phases of the two holograms do not coincide exactly. Another finding is that pi-shifted holograms are much less affected by gain variations but show no improvement concerning geometric distortions. The resulting phase errors will be estimated and simulations presented that confirm the theoretical developments.
Collapse
Affiliation(s)
- Martin Hÿtch
- CEMES, Université de Toulouse, CNRS, 29 rue Jeanne Marvig, 31055 Toulouse, France
| | - Christophe Gatel
- CEMES, Université de Toulouse, CNRS, 29 rue Jeanne Marvig, 31055 Toulouse, France
| |
Collapse
|
4
|
Boureau V, Sklenard B, McLeod R, Ovchinnikov D, Dumcenco D, Kis A, Cooper D. Quantitative Mapping of the Charge Density in a Monolayer of MoS 2 at Atomic Resolution by Off-Axis Electron Holography. ACS NANO 2020; 14:524-530. [PMID: 31820927 DOI: 10.1021/acsnano.9b06716] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The electric potential, electric field, and charge density of a monolayer of MoS2 have been quantitatively measured at atomic-scale resolution. This has been performed by off-axis electron holography using a double aberration-corrected transmission electron microscope operated at 80 kV and a low electron beam current density. Using this low dose rate and acceleration voltage, the specimen damage is limited during imaging. In order to improve the sensitivity of the measurement, a series of holograms have been acquired. Instabilities of the microscope such as the drifts of the specimen, biprism, and optical aberrations during the acquisition have been corrected by data processing. Phase images of the MoS2 monolayer have been acquired with a sensitivity of 2π/698 rad associated with a spatial resolution of 2.4 Å. The improvement in the signal-to-noise ratio allows the charge density to be directly calculated from the phase images using Poisson's equation. Density functional theory simulations of the potential and charge density of this MoS2 monolayer were performed for comparison to the experiment. The experimental measurements and simulations are consistent with each other, and notably, the charge density in a sulfur monovacancy (VS) site is shown.
Collapse
Affiliation(s)
- Victor Boureau
- Université Grenoble Alpes, CEA, LETI , F-38054 Grenoble , France
| | - Benoit Sklenard
- Université Grenoble Alpes, CEA, LETI , F-38054 Grenoble , France
| | - Robert McLeod
- Université Grenoble Alpes, CEA, INAC , F-38054 Grenoble , France
| | - Dmitry Ovchinnikov
- Electrical Engineering Institute , Ecole Polytechnique Federale de Lausanne , CH-1015 Lausanne , Switzerland
| | - Dumitru Dumcenco
- Electrical Engineering Institute , Ecole Polytechnique Federale de Lausanne , CH-1015 Lausanne , Switzerland
| | - Andras Kis
- Electrical Engineering Institute , Ecole Polytechnique Federale de Lausanne , CH-1015 Lausanne , Switzerland
| | - David Cooper
- Université Grenoble Alpes, CEA, LETI , F-38054 Grenoble , France
| |
Collapse
|
5
|
Nanosecond electron holography by interference gating. Ultramicroscopy 2019; 206:112824. [PMID: 31401353 DOI: 10.1016/j.ultramic.2019.112824] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 07/19/2019] [Accepted: 07/26/2019] [Indexed: 11/24/2022]
Abstract
The interference gating is a novel method for robust time-resolved electron holographic measurements by directly switching the interference. Here, a new arrangement is presented in which a biprism in the condenser aperture as a fast electric phase shifter is used to control the interference pattern. High-frequency stimulation of the electric phase shifter in the gigahertz range are performed and observed via electron holography, proving the feasibility of interference gating in the upper picosecond range. Despite the bandwidth limitation of 180 MHz of the current signal generator, a time resolution of 100 ns is achieved through forward correction of the control signal. With this time resolution, it is already possible to measure the transient response of the biasing holder system. Our method paves the way towards a closer look on fast dynamic processes with high temporal and spatial resolution.
Collapse
|
6
|
Off-axis electron holography combining summation of hologram series with double-exposure phase-shifting: Theory and application. Ultramicroscopy 2018; 193:52-63. [DOI: 10.1016/j.ultramic.2018.06.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 05/30/2018] [Accepted: 06/03/2018] [Indexed: 11/23/2022]
|
7
|
Gated interference for time-resolved electron holography. Ultramicroscopy 2017; 182:54-61. [PMID: 28654828 DOI: 10.1016/j.ultramic.2017.06.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/13/2017] [Accepted: 06/18/2017] [Indexed: 11/21/2022]
Abstract
Pump-probe measurements of periodic processes require a temporal gating for the time-dependent signal. For this purpose we propose to take advantage of the sensitivity of interferometric techniques like electron holography to instabilities. We have realized such a gating by synchronized disturbances of the measurement setup and successfully conducted measurements of electric fields with microsecond time resolution.
Collapse
|
8
|
Performance of a direct detection camera for off-axis electron holography. Ultramicroscopy 2016; 161:90-97. [DOI: 10.1016/j.ultramic.2015.09.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 08/21/2015] [Accepted: 09/11/2015] [Indexed: 11/22/2022]
|
9
|
Röder F, Lubk A. A proposal for the holographic correction of incoherent aberrations by tilted reference waves. Ultramicroscopy 2015; 152:63-74. [DOI: 10.1016/j.ultramic.2015.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 01/14/2015] [Accepted: 01/31/2015] [Indexed: 11/30/2022]
|
10
|
Chang SL, Dwyer C, Boothroyd CB, Dunin-Borkowski RE. Optimising electron holography in the presence of partial coherence and instrument instabilities. Ultramicroscopy 2015; 151:37-45. [DOI: 10.1016/j.ultramic.2014.11.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 11/10/2014] [Accepted: 11/10/2014] [Indexed: 11/24/2022]
|
11
|
Dwyer C, Boothroyd C, Chang S, Dunin-Borkowski R. Three-wave electron vortex lattices for measuring nanofields. Ultramicroscopy 2015; 148:25-30. [DOI: 10.1016/j.ultramic.2014.08.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Revised: 08/18/2014] [Accepted: 08/21/2014] [Indexed: 11/16/2022]
|
12
|
Genz F, Niermann T, Buijsse B, Freitag B, Lehmann M. Advanced double-biprism holography with atomic resolution. Ultramicroscopy 2014; 147:33-43. [DOI: 10.1016/j.ultramic.2014.06.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Revised: 06/05/2014] [Accepted: 06/08/2014] [Indexed: 10/25/2022]
|