Physikalisches Kolloquium: Holography and coherent diffraction imaging with electrons, light and X-rays

Jan 19
January 19, 2022 12:00 pm - 1:00 pm
HH und Online via Zoom

Holography and coherent diffraction imaging with electrons, light and X-rays

Lens-less imaging techniques employ no lenses between the sample and detector, they are aberration-free and therefore potentially can provide the highest possible resolution of the imaged samples. Two most common lens-less imaging techniques are holography and coherent diffraction imaging (CDI).
Holography captures the complex-valued distribution of the scattered wave by adding a reference wave (1). Holography has been realized with light, electrons, X-ray and other waves. Principles of in-line (Gabor-type) and off axis holographic schemes will be presented. Low-energy (30 – 300 eV) in-line electron holography will be discussed in more details including: a specially designed electron microscope arrangement (2), sample preparation, holograms acquisition and reconstructions. Examples of imaging of individual macromolecules such as proteins (3, 4) and individual charged impurities on graphene (5).
In CDI, diffraction pattern of a sample is recorded in the far field, the sample structure is reconstructed from the diffraction pattern by applying an iterative phase retrieval algorithm (6). Although CDI has been mainly designed for imaging with X-rays where no lenses are available, it has also been demonstrated with electrons, Zuo et al reported imaging of a double-walled carbon nano-tube at 1 Å resolution by CDI (7). The required experimental conditions (oversampling), the iterative phase retrieval algorithms (8), the reliability of the algorithms and uniqueness of the recovered structures will be discussed.
The presented lens-less imaging techniques: holography, CDI, ptychography will be compared; the latest results, current challenges and resolution limits will be discussed.
1. D. Gabor, A new microscopic principle. Nature 161, 777–778 (1948).
2. H.-W. Fink, W. Stocker, H. Schmid, Holography with low-energy electrons. Phys. Rev. Lett. 65, 1204–1206 (1990).
3. T. Latychevskaia, J.-N. Longchamp, C. Escher, H.-W. Fink, in Advancing Methods for Biomolecular Crystallography. (Springer, 2013), pp. 331–342.
4. J.-N. Longchamp et al., Imaging proteins at the single-molecule level. PNAS 114, 1474–1479 (2017).
5. T. Latychevskaia, F. Wicki, J.-N. Longchamp, C. Escher, H.-W. Fink, Direct observation of individual charges and their dynamics on graphene by low-energy electron holography. Nano Lett. 16, 5469–5474 (2016).
6. J. W. Miao, P. Charalambous, J. Kirz, D. Sayre, Extending the methodology of X-ray crystallography to allow imaging of micrometre-sized non-crystalline specimens. Nature 400, 342–344 (1999).
7. J. M. Zuo, I. Vartanyants, M. Gao, R. Zhang, L. A. Nagahara, Atomic resolution imaging of a carbon nanotube from diffraction intensities. Science 300, 1419–1421 (2003).
8. T. Latychevskaia, Iterative phase retrieval in coherent diffractive imaging: practical issues. Appl. Opt. 57, 7187–7197 (2018).

Sprecherin: PD Tatiana Latychevskaia, Paul Scherrer Institute, University of Zurich

Kontakt: Prof. Peter Hommelhoff

Norbert Lindlein lädt Sie zu einem geplanten Zoom-Meeting ein.

Thema: Physikalisches Kolloquium WS 2021/2022
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