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Holography and Coherent Diffraction Imaging with Low-(30-250 eV) and High-(80-300 keV) Energy Electrons: History, Principles, and Recent Trends. MATERIALS 2020; 13:ma13143089. [PMID: 32664297 PMCID: PMC7412140 DOI: 10.3390/ma13143089] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 07/04/2020] [Accepted: 07/07/2020] [Indexed: 01/02/2023]
Abstract
In this paper, we present the theoretical background to electron scattering in an atomic potential and the differences between low- and high-energy electrons interacting with matter. We discuss several interferometric techniques that can be realized with low- and high-energy electrons and which can be applied to the imaging of non-crystalline samples and individual macromolecules, including in-line holography, point projection microscopy, off-axis holography, and coherent diffraction imaging. The advantages of using low- and high-energy electrons for particular experiments are examined, and experimental schemes for holography and coherent diffraction imaging are compared.
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Salançon E, Degiovanni A, Lapena L, Morin R. High spatial resolution detection of low-energy electrons using an event-counting method, application to point projection microscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:043301. [PMID: 29716327 DOI: 10.1063/1.5020255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
An event-counting method using a two-microchannel plate stack in a low-energy electron point projection microscope is implemented. 15 μm detector spatial resolution, i.e., the distance between first-neighbor microchannels, is demonstrated. This leads to a 7 times better microscope resolution. Compared to previous work with neutrons [Tremsin et al., Nucl. Instrum. Methods Phys. Res., Sect. A 592, 374 (2008)], the large number of detection events achieved with electrons shows that the local response of the detector is mainly governed by the angle between the hexagonal structures of the two microchannel plates. Using this method in point projection microscopy offers the prospect of working with a greater source-object distance (350 nm instead of 50 nm), advancing toward atomic resolution.
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Affiliation(s)
- Evelyne Salançon
- Aix Marseille University, CNRS, CINAM UMR 7325, F-13288 Marseille, France
| | - Alain Degiovanni
- Aix Marseille University, CNRS, CINAM UMR 7325, F-13288 Marseille, France
| | - Laurent Lapena
- Aix Marseille University, CNRS, CINAM UMR 7325, F-13288 Marseille, France
| | - Roger Morin
- Aix Marseille University, CNRS, CINAM UMR 7325, F-13288 Marseille, France
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Latychevskaia T. Spatial coherence of electron beams from field emitters and its effect on the resolution of imaged objects. Ultramicroscopy 2016; 175:121-129. [PMID: 28236742 DOI: 10.1016/j.ultramic.2016.11.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Revised: 11/01/2016] [Accepted: 11/08/2016] [Indexed: 11/18/2022]
Abstract
Sub-nanometer and nanometer-sized tips provide high coherence electron sources. Conventionally, the effective source size is estimated from the extent of the experimental biprism interference pattern created on the detector by applying the van Cittert Zernike theorem. Previously reported experimental intensity distributions on the detector exhibit Gaussian distribution and our simulations show that this is an indication that such electron sources must be at least partially coherent. This, in turn means that strictly speaking the Van Cittert Zernike theorem cannot be applied, since it assumes an incoherent source. The approach of applying the van Cittert Zernike theorem is examined in more detail by performing simulations of interference patterns for the electron sources of different size and different coherence length, evaluating the effective source size from the extent of the simulated interference pattern and comparing the obtained result with the pre-defined value. The intensity distribution of the source is assumed to be Gaussian distributed, as it is observed in experiments. The visibility or the contrast in the simulated holograms is found to be always less than 1 which agrees well with previously reported experimental results and thus can be explained solely by the Gaussian intensity distribution of the source. The effective source size estimated from the extent of the interference pattern turns out to be of about 2-3 times larger than the pre-defined size, but it is approximately equal to the intrinsic resolution of the imaging system. A simple formula for estimating the intrinsic resolution, which could be useful when employing nano-tips in in-line Gabor holography or point-projection microscopy, is provided.
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Affiliation(s)
- Tatiana Latychevskaia
- Physics Department of the University of Zurich, Winterthurerstrasse 190, Zurich, 8057 Switzerland.
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Ehberger D, Hammer J, Eisele M, Krüger M, Noe J, Högele A, Hommelhoff P. Highly Coherent Electron Beam from a Laser-Triggered Tungsten Needle Tip. PHYSICAL REVIEW LETTERS 2015. [PMID: 26196645 DOI: 10.1103/physrevlett.114.227601] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We report on a quantitative measurement of the spatial coherence of electrons emitted from a sharp metal needle tip. We investigate the coherence in photoemission triggered by a near-ultraviolet laser with a photon energy of 3.1 eV and compare it to dc-field emission. A carbon nanotube is brought into close proximity to the emitter tip to act as an electrostatic biprism. From the resulting electron matter wave interference fringes, we deduce an upper limit of the effective source radius both in laser-triggered and dc-field emission mode, which quantifies the spatial coherence of the emitted electron beam. We obtain (0.80±0.05) nm in laser-triggered and (0.55±0.02) nm in dc-field emission mode, revealing that the outstanding coherence properties of electron beams from needle tip field emitters are largely maintained in laser-induced emission. In addition, the relative coherence width of 0.36 of the photoemitted electron beam is the largest observed so far. The preservation of electronic coherence during emission as well as ramifications for time-resolved electron imaging techniques are discussed.
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Affiliation(s)
- Dominik Ehberger
- Department of Physics, Friedrich Alexander University Erlangen-Nuremberg, Staudtstrasse 1, D-91058 Erlangen, Germany, EU
- Max Planck Institute of Quantum Optics, Hans-Kopfermann-Strasse 1, D-85748 Garching/Munich, Germany, EU
| | - Jakob Hammer
- Department of Physics, Friedrich Alexander University Erlangen-Nuremberg, Staudtstrasse 1, D-91058 Erlangen, Germany, EU
- Max Planck Institute of Quantum Optics, Hans-Kopfermann-Strasse 1, D-85748 Garching/Munich, Germany, EU
| | - Max Eisele
- Max Planck Institute of Quantum Optics, Hans-Kopfermann-Strasse 1, D-85748 Garching/Munich, Germany, EU
| | - Michael Krüger
- Department of Physics, Friedrich Alexander University Erlangen-Nuremberg, Staudtstrasse 1, D-91058 Erlangen, Germany, EU
- Max Planck Institute of Quantum Optics, Hans-Kopfermann-Strasse 1, D-85748 Garching/Munich, Germany, EU
| | - Jonathan Noe
- Fakultät für Physik and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, 80539 München, Germany, EU
| | - Alexander Högele
- Fakultät für Physik and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, 80539 München, Germany, EU
| | - Peter Hommelhoff
- Department of Physics, Friedrich Alexander University Erlangen-Nuremberg, Staudtstrasse 1, D-91058 Erlangen, Germany, EU
- Max Planck Institute of Quantum Optics, Hans-Kopfermann-Strasse 1, D-85748 Garching/Munich, Germany, EU
- Max Planck Institute for the Science of Light, Günther-Scharowsky-Strasse 1/ Building 24, D-91058 Erlangen, Germany, EU
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Müller M, Paarmann A, Ernstorfer R. Femtosecond electrons probing currents and atomic structure in nanomaterials. Nat Commun 2014; 5:5292. [DOI: 10.1038/ncomms6292] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 09/17/2014] [Indexed: 11/09/2022] Open
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Latychevskaia T, Longchamp JN, Escher C, Fink HW. On artefact-free reconstruction of low-energy (30-250eV) electron holograms. Ultramicroscopy 2013; 145:22-7. [PMID: 24331233 DOI: 10.1016/j.ultramic.2013.11.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Revised: 11/11/2013] [Accepted: 11/21/2013] [Indexed: 11/17/2022]
Abstract
Low-energy electrons (30-250eV) have been successfully employed for imaging individual biomolecules. The most simple and elegant design of a low-energy electron microscope for imaging biomolecules is a lensless setup that operates in the holographic mode. In this work we address the problem associated with the reconstruction from the recorded holograms. We discuss the twin image problem intrinsic to inline holography and the problem of the so-called biprism-like effect specific to low-energy electrons. We demonstrate how the presence of the biprism-like effect can be efficiently identified and circumvented. The presented sideband filtering reconstruction method eliminates the twin image and allows for reconstruction despite the biprism-like effect, which we demonstrate on both, simulated and experimental examples.
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Affiliation(s)
- Tatiana Latychevskaia
- Physics Institute, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
| | - Jean-Nicolas Longchamp
- Physics Institute, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Conrad Escher
- Physics Institute, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Hans-Werner Fink
- Physics Institute, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Stoll JD, Kolmakov A. Electron transparent graphene windows for environmental scanning electron microscopy in liquids and dense gases. NANOTECHNOLOGY 2012; 23:505704. [PMID: 23165114 DOI: 10.1088/0957-4484/23/50/505704] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Due to its ultrahigh electron transmissivity in a wide electron energy range, molecular impermeability, high electrical conductivity and excellent mechanical stiffness, suspended graphene membranes appear to be a nearly ideal window material for in situ (in vivo) environmental electron microscopy of nano- and mesoscopic objects (including bio-medical samples) immersed in liquids and/or in dense gaseous media. In this paper, taking advantage of a small modification of the graphene transfer protocol onto metallic and SiN supporting orifices, reusable environmental cells with exchangeable graphene windows have been designed. Using colloidal gold nanoparticles (50 nm) dispersed in water as model objects for scanning electron microscopy in liquids as proof of concept, different conditions for imaging through the graphene membrane were tested. Limiting factors for electron microscopy in liquids, such as electron beam induced water radiolysis and damage of the graphene membrane at high electron doses, are discussed.
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Affiliation(s)
- Joshua D Stoll
- Department of Physics, Southern Illinois University, Carbondale, IL 62901, USA
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Ptychographic electron microscopy using high-angle dark-field scattering for sub-nanometre resolution imaging. Nat Commun 2012; 3:730. [PMID: 22395621 PMCID: PMC3316878 DOI: 10.1038/ncomms1733] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Accepted: 02/06/2012] [Indexed: 11/10/2022] Open
Abstract
Diffractive imaging, in which image-forming optics are replaced by an inverse computation using scattered intensity data, could, in principle, realize wavelength-scale resolution in a transmission electron microscope. However, to date all implementations of this approach have suffered from various experimental restrictions. Here we demonstrate a form of diffractive imaging that unshackles the image formation process from the constraints of electron optics, improving resolution over that of the lens used by a factor of five and showing for the first time that it is possible to recover the complex exit wave (in modulus and phase) at atomic resolution, over an unlimited field of view, using low-energy (30 keV) electrons. Our method, called electron ptychography, has no fundamental experimental boundaries: further development of this proof-of-principle could revolutionize sub-atomic scale transmission imaging. Diffractive imaging can deliver wavelength-scale resolution with X-rays, although its use with electrons is hampered by experimental constraints. By applying ptychographic methods to transmission electron microscopy, Humphry et al. demonstrate sub-nanometre resolution using low-energy electrons.
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Vieker H, Beyer A, Blank H, Weber DH, Gerthsen D, Gölzhäuser A. Low Energy Electron Point Source Microscopy of Two-Dimensional Carbon Nanostructures. Z PHYS CHEM 2011. [DOI: 10.1524/zpch.2011.0191] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
1 nm thick carbon nanomembranes (CNMs) are investigated with Low Energy Electron Point Source (LEEPS) microscopy. A CNM consists of a freely suspended carbon film made from a cross-linked self-assembled monolayer (SAM). During thermal annealing the CNM transforms into nanocrystalline graphene.We determined the electron transmissivity of CNMs from the LEEPS images. After pyrolysis, the LEEPS images showed clear differences compared to pristine CNMs. Upon annealing above 800 ºC the LEEPS images exhibit distinct features that are related to the structural transition. A comparison of LEEPS images with transmission electron micrographs of the same regions and features demonstrates that both microscopic techniques reveal similar structural features.
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Affiliation(s)
- Henning Vieker
- University of Bielefeld, Physics of Supramolecular Systems and Surfaces, Bielefeld, Deutschland
| | - André Beyer
- University of Bielefeld, Physics of Supramolecular Systems and Surfaces, Bielefeld, Deutschland
| | - Holger Blank
- Karlsruhe Institute of Technology, Laboratory for Electron Microscopy, Karlsruhe, Deutschland
| | - Dirk Henning Weber
- University of Bielefeld, Physics of Supramolecular Systems and Surfaces, Bielefeld, Deutschland
| | - Dagmar Gerthsen
- Karlsruhe Institute of Technology, Laboratory for Electron Microscopy, Karlsruhe, Deutschland
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