Holographic Image Reconstruction from Electron Diffraction Intensities of Ordered Superstructures

Reuter, Karsten; Bernhardt, J.; Wedler, H.; Schardt, J.; Starke, Ulrich; Heinz, K.

doi:10.1103/physrevlett.79.4818

Cited by 64 publications

(68 citation statements)

References 20 publications

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“…This ensures that the protein is held at a fixed angle determined by the dipole moment of the dye and will be particularly effective if the molecule is sufficiently laser cooled. For the DNA sequencing the electron beam is focused to a diameter of 2-3 nm ͑20-30 Å͒, and because the beam is effectively coherent, it is possible to make a hologram 8 of the base pairs in the beam. However for a rapid sequencing it will only be necessary to obtain a signature in the diffraction pattern from several detectors positioned around the focal spot as the beam is scanned along the strand.…”

Section: Discussionmentioning

confidence: 99%

A design for a subminiature, low energy scanning electron microscope with atomic resolution

Eastham

Edmondson

Greene

et al. 2009

Journal of Applied Physics

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We describe a type of scanning electron microscope that works by directly imaging the electron field-emission sites on a nanotip. Electrons are extracted from the nanotip through a nanoscale aperture, accelerated in a high electric field, and focused to a spot using a microscale Einzel lens. If the whole microscope ͑accelerating section and lens͒ and the focal length are both restricted in size to below 10 m, then computer simulations show that the effects of aberration are extremely small and it is possible to have a system with approximately unit magnification at electron energies as low as 300 eV. Thus a typical emission site of 1 nm diameter will produce an image of the same size, and an atomic emission site will give a resolution of 0.1-0.2 nm ͑1-2 Å͒. Also, because the beam is not allowed to expand beyond 100 nm in diameter, the depth of field is large and the contribution to the beam spot size from chromatic aberrations is less than 0.02 nm ͑0.2 Å͒ for 500 eV electrons. Since it is now entirely possible to make stable atomic sized emitters ͑nanopyramids͒, it is expected that this instrument will have atomic resolution. Furthermore the brightness of the beam is determined only by the field emission and can be up to 1 ϫ 10 6 times larger than in a typical ͑high energy͒ electron microscope. The advantages of this low energy, bright-beam electron microscope with atomic resolution are described and include the possibility of it being used to rapidly sequence the human genome from a single strand of DNA as well as being able to identify atomic species directly from the elastic scattering of electrons.

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Section: Discussionmentioning

confidence: 99%

A design for a subminiature, low energy scanning electron microscope with atomic resolution

Eastham

Edmondson

Greene

et al. 2009

Journal of Applied Physics

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show abstract

“…The limited interaction between the reference wave and the object produces scattered waves, however, and these interfere with the reference wave to produce the diffraction pattern or hologram. This may then be Fourier transformed to produce an atomic image of the local surface area (Barton, 1990;Fadley et al, 1997;Len et al, 1995;Reuter et al, 1997;Saldin, 1997).…”

Section: Photoelectron Holography (Peh)mentioning

confidence: 99%

Electron crystallography in surface structure analysis

Leslie

Landree

Collazo-Davila

et al. 1999

Microsc. Res. Tech.

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“…This is because the signal is rather weak and strong Bragg spots caused by the substrate are superimposed which blurs the signal sought, especially at higher energies when beams get crowded. Therefore, the idea of using ordered arrays of beam splitters causing discrete superstructure beams rather than diffuse intensities [27] and the eventual successful application in image reconstruction [28] allowed the use of more reliable data, and at the same time extended LEED holography to ordered superstructures. We address this in the next section.…”

Section: Real-space Images From Diffuse Intensity Distributionsmentioning

confidence: 99%

“…Yet, the situation can become substantially worse, Figure 6. Reconstruction of the atomic cluster below the beam splitter (upper left, repeated schematically on the right) from discrete LEED spot intensities of SiC(111)-(3 × 3) (after reference [28]). In the lower panel the full structure is displayed, as resulting from a conventional LEED analysis [31,32] with the cluster (heavily shaded) as input.…”

Section: Missing Atoms False Atoms and False Atom Positionsmentioning

confidence: 99%

Holographic low-energy electron diffraction

Heinz

Seubert

Saldin

2001

J. Phys.: Condens. Matter

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In holographic low-energy electron diffraction an atom protruding from a surface acts as a beam splitter for the incoming electron beam, creating a reference wave and, by subsequent substrate scattering, an object wave. In this sense, the method corresponds closely to traditional optical holography. The present power of the technique is demonstrated and sources of image degradation are pointed out. Additionally, we describe new developments designed to reduce the influence of the corresponding disturbing scattering processes. These are concerned in particular with the appearance of false atoms and incorrect atom positions. It will be demonstrated that these features can be avoided by the use of a proper kernel in the transform integral. Also, an iterative reconstruction procedure can be applied. This can also be used to reduce the influence of substrate reconstructions induced by the beam splitter, but, in that case, a hybrid of a reconstruction and a data-fitting procedure is applied. Adatoms on surfaces as holographic beam splittersIt is well known that Gabor's original ideas concerning holography concentrated on electrons (to improve the resolution in electron microscopy) rather than on optical holography [1]. Yet, he was well aware of the intrinsic obstacles hindering the rapid realization of his ideas at the time. For using electrons he had to concede that . . . in light optics a coherent background can be produced in many ways, but electron optics does not possess effective beam splitting devices . . . [2]. The coherent background was meant to provide the reference wave R which is made to interfere with the wave diffracted by the object, i.e. the object wave O, in order to form the hologram. The corresponding set-up is indicated schematically on the left of figure 1, using photons rather than electrons as has become possible since the arrival of the laser. The use of a simple semi-transparent mirror as a beam splitter and the excellent coherence properties of lasers (typical order of coherence length L c : ≈10 m) guarantee that R and O can interfere, as

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Holographic Image Reconstruction from Electron Diffraction Intensities of Ordered Superstructures

Cited by 64 publications

References 20 publications

A design for a subminiature, low energy scanning electron microscope with atomic resolution

A design for a subminiature, low energy scanning electron microscope with atomic resolution

Electron crystallography in surface structure analysis

Holographic low-energy electron diffraction

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