We have developed an efficient detector of secondary electrons (SEs) for a high-performance scanning transmission electron microscope (STEM) and tested it on several materials. Using the detector at 60 keV, we resolved the nearest neighbor atoms separated by 0.142 nm in SE images of graphene, and detected single-atom substitutions in graphene and monolayer MoS2. We imaged single heavy atoms on an amorphous carbon thin film, and the surface structure of gold nanoparticles supported on a thin film as well as on a bulk substrate. Other application examples shown in this paper include SE imaging combined with 4D STEM, simultaneous SE and electron energy loss spectroscopy (EELS) imaging, and simultaneous imaging of entrance and exit sides of a sample using two separate SE detectors. The results point to an exciting future for atomic-resolution SE imaging.

Journal Article Unveiling Phonon Dispersion Behavior of AlN/GaN Heterostructures Using EELS Get access Joaquin E Reyes-González, Joaquin E Reyes-González Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada Search for other works by this author on: Oxford Academic Google Scholar Niklas Dellby, Niklas Dellby Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Benjamin Plotkin-Swing, Benjamin Plotkin-Swing Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Ping Wang, Ping Wang Department of Electrical and Computer Engineering, University of Michigan, Ann Arbor, Michigan, United States Search for other works by this author on: Oxford Academic Google Scholar Ayush Pandey, Ayush Pandey Department of Electrical and Computer Engineering, University of Michigan, Ann Arbor, Michigan, United States Search for other works by this author on: Oxford Academic Google Scholar Zetian Mi, Zetian Mi Department of Electrical and Computer Engineering, University of Michigan, Ann Arbor, Michigan, United States Search for other works by this author on: Oxford Academic Google Scholar Maureen J Lagos Maureen J Lagos Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario, CanadaCanadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario, Canada Corresponding author: mjlagos@mcmaster.ca Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Pages 354–355, https://doi.org/10.1093/micmic/ozad067.165 Published: 22 July 2023

Vibrations in materials and nanostructures at sufficiently high temperatures result in anharmonic atomic displacements, which leads to new phenomena such as thermal expansion and multiphonon scattering processes, with a profound impact on temperature-dependent material properties including thermal conductivity, phonon lifetimes, nonradiative electronic transitions, and phase transitions. Nanoscale momentum-resolved vibrational spectroscopy, which has recently become possible on monochromated scanning-transmission-electron microscopes, is a unique method to probe the underpinnings of these phenomena. Here we report momentum-resolved vibrational spectroscopy in hexagonal boron nitride at temperatures of 300, 800, and 1300 K across three Brillouin zones (BZs) that reveals temperature-dependent phonon energy shifts and demonstrates the presence of strong Umklapp processes. Density-functional-theory calculations of temperature-dependent phonon self-energies reproduce the observed energy shifts and identify the contributing mechanisms.

Journal Article Multi-Sun EELS: Ultra-High Energy Resolution combined with High Spatial Resolution and High Beam Current Get access N Dellby, N Dellby Nion R&D, 11511 NE 118th St, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar OL Krivanek, OL Krivanek Nion R&D, 11511 NE 118th St, Kirkland, WA, USADepartment of Physics, Arizona State University, Tempe AZ, USA Search for other works by this author on: Oxford Academic Google Scholar NJ Bacon, NJ Bacon Nion R&D, 11511 NE 118th St, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar GJ Corbin, GJ Corbin Nion R&D, 11511 NE 118th St, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar N Johnson, N Johnson Nion R&D, 11511 NE 118th St, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar R Hayner, R Hayner Nion R&D, 11511 NE 118th St, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar P Hrncrik, P Hrncrik Nion R&D, 11511 NE 118th St, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar B Plotkin-Swing, B Plotkin-Swing Nion R&D, 11511 NE 118th St, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar D Taylor, D Taylor Nion R&D, 11511 NE 118th St, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar ZS Szilaygi, ZS Szilaygi Nion R&D, 11511 NE 118th St, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar ... Show more TC Lovejoy TC Lovejoy Nion R&D, 11511 NE 118th St, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 2640–2642, https://doi.org/10.1017/S1431927622010017 Published: 01 August 2022

Journal Article 100,000 Diffraction Patterns per Second with Live Processing for 4D-STEM Get access Benjamin Plotkin-Swing, Benjamin Plotkin-Swing Nion Co. R&D, Kirkland, WA, USA Corresponding author: plotkin-swing@nion.com Search for other works by this author on: Oxford Academic Google Scholar Benedikt Haas, Benedikt Haas Department of Physics & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin, Germany Search for other works by this author on: Oxford Academic Google Scholar Andreas Mittelberger, Andreas Mittelberger Nion Co. R&D, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Niklas Dellby, Niklas Dellby Nion Co. R&D, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Michael Hotz, Michael Hotz Nion Co. R&D, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Petr Hrncirik, Petr Hrncirik Nion Co. R&D, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Chris Meyer, Chris Meyer Department of Physics & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin, Germany Search for other works by this author on: Oxford Academic Google Scholar Pietro Zambon, Pietro Zambon DECTRIS Ltd., Baden-Daettwil, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Christoph Hoermann, Christoph Hoermann DECTRIS Ltd., Baden-Daettwil, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Matthias Meffert, Matthias Meffert DECTRIS Ltd., Baden-Daettwil, Switzerland Search for other works by this author on: Oxford Academic Google Scholar ... Show more Darya Bachevskaya, Darya Bachevskaya DECTRIS Ltd., Baden-Daettwil, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Luca Piazza, Luca Piazza DECTRIS Ltd., Baden-Daettwil, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Ondrej L Krivanek, Ondrej L Krivanek Nion Co. R&D, Kirkland, WA, USADepartment of Physics, Arizona State University, Tempe AZ, USA Search for other works by this author on: Oxford Academic Google Scholar Tracy Clark Lovejoy Tracy Clark Lovejoy Nion Co. R&D, Kirkland, WA, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 422–424, https://doi.org/10.1017/S1431927622002392 Published: 01 August 2022

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4D-STEM acquisition using fast pixelated detectors continues to have a strong impact on the electron microscopy community [1]. It has recently been shown that acquiring and (non-rigidly) registering series of 4D maps can substantially improve the quality of the data, especially for methods like center-of-mass analysis (COM) that rely on assuming correct beam positions and are sensitive to deviations [2]. However, the collection of 4D-STEM series produces massive amounts of data and it is normally necessary to either interrupt the microscopy session to pre-process on the side to roughly assess the data quality before resuming the next measurements or to store and process the data sets afterwards and only then have a full understanding of its quality. Therefore, the handling of those data sets is cumbersome and microscopy time and/or storage space are typically wasted in the process of acquiring good data, especially if one needs a series of 4D-STEM data. Here, we present live processing at over 15’000 frames per second of a Dectris ELA direct detector [3] mounted on an IRIS spectrometer of a Nion HERMES microscope. The Dectris ELA detector is suitable for EELS measurements, and also for 4D-STEM. It combines the readout noise-free characteristics known from hybrid-pixel detectors with a relatively large number of pixels (1030x514), very high frame rates (up to 18’000 for 1030x130 pixel readout) and a high

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Vibrational spectroscopy in the electron microscope [1] was recently made possible by combining stable monochromators with ultra-stable electron energy loss (EEL) spectrometers, and continues to progress rapidly. The Nion Iris spectrometer [2] incorporated into the Nion High Energy Resolution Monochromated EELSSTEM (HERMESTM) system has led to an EELS era in which < 5 meV energy resolution can be attained at 30 keV primary energy and below. In combination with atom-sized electron probes, introduced just 6 years ago, vibrational spectroscopy has already achieved:

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Journal Article Damage-free Analysis of Biological Materials by Vibrational Spectroscopy in the EM Get access Ondrej Krivanek, Ondrej Krivanek Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Alice Dohnalkova, Alice Dohnalkova Pacific Northwest National Laboratory, Richland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Zdravko Kochovski, Zdravko Kochovski Institute of Electrochemical Energy Storage, Berlin, Berlin, Germany Search for other works by this author on: Oxford Academic Google Scholar Benedikt Haas, Benedikt Haas Humboldt-Universität zu Berlin, Berlin, Berlin, Germany Search for other works by this author on: Oxford Academic Google Scholar Johannes Müller, Johannes Müller Humboldt-Universität zu Berlin, Berlin, Berlin, Germany Search for other works by this author on: Oxford Academic Google Scholar Niklas Dellby, Niklas Dellby Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Michael Hotz, Michael Hotz Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Andreas Mittelberger, Andreas Mittelberger Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Benjamin Plotkin-Swing, Benjamin Plotkin-Swing Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Tracy Lovejoy, Tracy Lovejoy Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar ... Show more Christoph Koch Christoph Koch Humboldt-Universität zu Berlin, Berlin, Berlin, Germany Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 26, Issue S2, 1 August 2020, Pages 108–110, https://doi.org/10.1017/S1431927620013409 Published: 01 August 2020

We characterize a hybrid pixel direct detector and demonstrate its suitability for electron energy loss spectroscopy (EELS). The detector has a large dynamic range, narrow point spread function, detective quantum efficiency >= 0.8 even without single electron arrival discrimination, and it is resilient to radiation damage. It is capable of detecting similar to 5 x 10(6) electrons/pixel/second, allowing it to accommodate up to 0.8 pA per pixel and hence > 100 pA EELS zero-loss peak (ZLP) without saturation, if the ZLP is spread over > 125 pixels (in the nondispersion direction). At the same time, it can reliably detect isolated single electrons in the high loss region of the spectrum. The detector uses a selectable threshold to exclude low energy events, and this results in essentially zero dark current and readout noise. Its maximum frame readout rate at 16-bit digitization is 2250 full frames per second, allowing for fast spectrum imaging. We show applications including EELS of boron nitride in which an unsaturated zero loss peak is recorded at the same time as inner shell loss edges, elemental mapping of an STO/BTO/LMSO multilayer, and efficient parallel acquisition of angle-resolved EEL spectra (S(q, omega)) of boron nitride.

We demonstrate a method to enhance the atom loading rate of a ytterbium (Yb) magneto-optic trap (MOT) operating on the 556 nm 1S0 → 3P1 intercombination transition (narrow linewidth Γg = 2π × 182 kHz). Following traditional Zeeman slowing of an atomic beam near the 399 nm 1S0 → 1P1 transition (broad linewidth Γp = 2π × 29 MHz), two laser beams in a crossed-beam geometry, frequency tuned near the same transition, provide additional slowing immediately prior to the MOT. Using this technique, we observe an improvement by a factor of 6 in the atom loading rate of a narrow-line Yb MOT. The relative simplicity and generality of this approach make it readily adoptable to other experiments involving narrow-line MOTs. We also present a numerical simulation of this two-stage slowing process, which shows good agreement with the observed dependence on experimental parameters, and use it to assess potential improvements to the method.

Journal Article Hybrid Pixel EELS Detector: Low Noise, High Speed, and Large Dynamic Range Get access Benjamin Plotkin-Swing, Benjamin Plotkin-Swing Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Tracy Lovejoy, Tracy Lovejoy Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Niklas Dellby, Niklas Dellby Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar George Corbin, George Corbin Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Matthew Hoffman, Matthew Hoffman Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Sacha De Carlo, Sacha De Carlo Dectris, Baden-Daettwil, Aargau, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Luca Piazza, Luca Piazza Dectris, Baden-Daettwil, Aargau, Switzerland Search for other works by this author on: Oxford Academic Google Scholar Chris Meyer, Chris Meyer Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Andreas Mittelberger, Andreas Mittelberger Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Ondrej Krivanek Ondrej Krivanek Nion Co., Kirkland, Washington, United States Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 26, Issue S2, 1 August 2020, Pages 1928–1930, https://doi.org/10.1017/S1431927620019856 Published: 01 August 2020

We apply a Bloch-bands approach to the analysis of pulsed optical standing wave diffractive elements in optics and interferometry with ultracold atoms. We verify our method by comparison to a series of experiments with Bose-Einstein condensates. The approach provides accurate Rabi frequencies for diffraction pulses and is particularly useful for the analysis and control of diffraction phases, an important systematic effect in precision atom interferometry. Utilizing this picture, we also demonstrate a method to determine atomic band structure in an optical lattice through a measurement of phase shifts in an atomic contrast interferometer.

Advances in the capabilities of scanning transmission electron microscopes (STEMs) and electron energy loss spectrometers (EELS) over the last 2 decades have been remarkable. Modern-day monochromated, aberration corrected STEMs (MAC-STEMs) can give probe sizes of 1.1 Å at 30 kV operating voltage [1], EELS energy resolution of 4.2 meV also at 30 kV [2], and spatial resolution of ~0.3 Å through the use of 4D STEM and ptychographic reconstruction [3]. These achievements have been made possible by aberration correction, and by developments in monochromator, spectrometer and detector design. The electron-optical developments are now maturing, and further improvements in this area are likely to be more incremental. Here we summarize our work on endowing Nion electron microscopes with new capabilities via new operation modes, detectors and software.

Large Momentum Separation Matter Wave Interferometry Benjamin T. Plotkin-Swing Chair of the Supervisory Committee: Subhadeep Gupta Dept. of Physics This work establishes a new benchmark for momentum separation in a matter wave interferometer with stable, visible fringes. With a path separation of 112 photon recoil momenta (112h̄k), our signal visibility of 30% and phase stability of 0.6rad exceed the performance of earlier free space interferometers. Contributing to this success are the symmetric form of the 3 path contrast interferometer geometry, which rejects phase noise due to vibrations and other systematic errors, the narrow momentum width of the Bose-Einstein condensate (BEC) source, and atom-optics parameters chosen to suppress unwanted diffraction phases. These results can be applied toward a competitive measurement of the fine-structure constant and a test of QED. The described experiments were performed in a new ytterbium BEC apparatus whose design, construction, and operation is documented here.