The extension of coherent lattice contrast into the energy loss region in high-resolution transmission electron microscopy (HRTEM) is described by a pulse-like electron-sample interaction in the energy/time uncertainty limit. It generates a wave packet by electron self-interference in any coherent-inelastic scattering event with energy loss. The width of this wave packet is characterized by a self-coherence length ls(ΔE) that is predictable because an intrinsic decoherence phase around one radian is set by the expectation value for phase fluctuations. In this case the visibility of interference contrast from a crystalline sample with lattice parameter a is limited by a Rayleigh-like transfer factor P(ls, a) in the self-coherently illuminated sample area. The model is verified by energy-filtered HRTEM images of hexagonal BN and identifies energy-loss-induced phase noise as a single-electron visibility limit distinct from resolution limitations caused by ensemble-coherence or counting-statistical noise.

The static and genuine structure of small rhodium and rhodium/tungsten nanoparticles on an alumina support can be imaged with atomic resolution even if single digit atom clusters are investigated. Low dose rate electron microscopy is key to the achievement and can generally be applied to investigate any similar material. In such conditions it becomes feasible to identify the chemical composition of nanocrystals from quantitative contrast analyses alone by counting atoms. The ability to fully characterize an unaltered, initial state of the objects allows targeting structural excitations or conformational changes induced by the electron beam itself. For the specific case of catalytic Rh:W particles we stimulate a tungsten-promoted size regulation mechanism in real time that is driven by Oswald ripening and can be understood by a strong binding of tungsten atoms to the oxygen atoms of the support, which builds up strain as the cluster sizes increase.

Intensities in high-resolution phase-contrast images from electron microscopes build up discretely in time by detecting single electrons. A wave description of pulse-like coherent-inelastic interaction of an electron with matter is detailed and verified. In perspective, the interaction time of any matter wave compares with the lifetime of a virtual particle of any elemental interaction, suggesting the present concept of coherent-inelastic interactions of matter waves might be generalizable.

The relation between the energy-dependent particle and wave descriptions of electron–matter interactions on the nanoscale was analyzed by measuring the delocalization of an evanescent field from energy-filtered amplitude images of sample/vacuum interfaces with a special aberration-corrected electron microscope. The spatial field extension coincided with the energy-dependent self-coherence length of propagating wave packets that obeyed the time-dependent Schrödinger equation, and underwent a Goos–Hänchen shift. The findings support the view that wave packets are created by self-interferences during coherent–inelastic Coulomb interactions with a decoherence phase close to Δφ = 0.5 rad. Due to a strictly reciprocal dependence on energy, the wave packets shrink below atomic dimensions for electron energy losses beyond 1000 eV, and thus appear particle-like. Consequently, our observations inevitably include pulse-like wave propagations that stimulate structural dynamics in nanomaterials at any electron energy loss, which can be exploited to unravel time-dependent structure–function relationships on the nanoscale.

Journal Article Probing Catalyst Surfaces at the Atomic-scale Get access M Ek, M Ek Topsoe A/S, Kgs. Lyngby, DenmarkCentre for Analysis and Synthesis & NanoLund, Lund University, Lund, Sweden Search for other works by this author on: Oxford Academic Google Scholar L P Hansen, L P Hansen Topsoe A/S, Kgs. Lyngby, Denmark Search for other works by this author on: Oxford Academic Google Scholar F R Chen, F R Chen Department of Materials Science and Engineering, City University of Hong Kong, Kowlook, Hong Kong Search for other works by this author on: Oxford Academic Google Scholar D van Dyck, D van Dyck Departments of Physics, EMAT, University of Antwerp, Antwerp, Belgium Search for other works by this author on: Oxford Academic Google Scholar C Kisielowski, C Kisielowski Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley CA, United States Search for other works by this author on: Oxford Academic Google Scholar P Specht, P Specht Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley CA, United States Search for other works by this author on: Oxford Academic Google Scholar C D Damsgaard, C D Damsgaard National Center for Nano Fabrication and Characterization, Technical University of Denmark, Kgs. Lyngby, DenmarkCenter for Visualizing Catalytic Processes (VISION), Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark Search for other works by this author on: Oxford Academic Google Scholar J R Jinschek, J R Jinschek National Center for Nano Fabrication and Characterization, Technical University of Denmark, Kgs. Lyngby, DenmarkCenter for Visualizing Catalytic Processes (VISION), Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark Search for other works by this author on: Oxford Academic Google Scholar S Helveg S Helveg Center for Visualizing Catalytic Processes (VISION), Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark Corresponding author: stig@fysik.dtu.dk Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Page 1291, https://doi.org/10.1093/micmic/ozad067.660 Published: 22 July 2023

Ultra‐low‐dose electron diffraction is performed with a double metal cyanide catalyst (DMC) to understand how electron irradiation stimulates structural alterations in functional materials. The commonly fading diffraction patterns with dose accumulation depend on the irradiated area and the beam current even when below 50 femto Amperes. Heat generation is observed and modeled by statistical, inelastic scattering events to describe how phonon excitations modulate radiation hardness. Specifically, the characteristic 1/e‐decay of Bragg intensities from DMC is delayed from 6 to 30 eÅ −2 at room temperature, which is comparable to the effect of embedding radiation soft matter in ice. DMC's radiation hardness is enhanced by a latency dose that forms during a phase transformation. This unifying model predicts that a critical dose rate exists for any material that varies between 0.1 and 10 4 eÅ −2 s −1 because of a material dependent competition of heat generation and spread. It shows that Brillouin scattering causes time dependent perturbations in electron irradiated solids that trigger time‐temperature‐transformations on a time scale of nanoseconds to microseconds at room temperature, which is not included in traditional models describing the decay of Bragg intensities by radiolysis.

The correlation between particle and wave descriptions of electron-matter interactions is analyzed by measuring the delocalization of an evanescent field using electron microscopy. Its spatial extension coincides with the energy-dependent, self-coherence length of propagating wave packets that obey the time-dependent Schrödinger equation and undergo a Goos-Hänchen shift. In the Heisenberg limit they are created by self-interferences during coherent-inelastic Coulomb interactions with a decoherence phase Δϕ = 0.5 rad and shrink to particle-like dimensions for energy losses of more than 1000 eV.

Journal Article Latency Dose Formation In DMC By Inelastic Electron Scattering Get access P Specht, P Specht Department of MSE, University of California Berkeley, Berkeley, CA 94720, USA Corresponding author: specht@berkeley.edu Search for other works by this author on: Oxford Academic Google Scholar C Kisielowski, C Kisielowski TMF, Lawrence Berkeley National Laboratory, One Cyclotron Rd., Berkeley, CA 94720, USA Search for other works by this author on: Oxford Academic Google Scholar B Freitag, B Freitag Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, The Netherlands Search for other works by this author on: Oxford Academic Google Scholar ER Kieft, ER Kieft Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, The Netherlands Search for other works by this author on: Oxford Academic Google Scholar S Rozeveld, S Rozeveld The Dow Chemical Company, Midland, MI 48667, USA Search for other works by this author on: Oxford Academic Google Scholar J Kang, J Kang The Dow Chemical Company, Midland, MI 48667, USA Search for other works by this author on: Oxford Academic Google Scholar AJ Fielitz, AJ Fielitz The Dow Chemical Company, Midland, MI 48667, USA Search for other works by this author on: Oxford Academic Google Scholar TR Fielitz, TR Fielitz The Dow Chemical Company, Midland, MI 48667, USA Search for other works by this author on: Oxford Academic Google Scholar D van Dyck, D van Dyck EMAT, University of Antwerp, 2020 Antwerp, Belgium Search for other works by this author on: Oxford Academic Google Scholar DF Yancey DF Yancey The Dow Chemical Company, Midland, MI 48667, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 2216–2217, https://doi.org/10.1017/S1431927622008558 Published: 01 August 2022

Journal Article Coherence and Inelastic Scattering in Electron Microscopy Get access C Kisielowski, C Kisielowski TMF, Lawrence Berkeley National Laboratory, One Cyclotron Rd., Berkeley, CA 94720, USA Corresponding author: CFKisielowski@lbl.gov Search for other works by this author on: Oxford Academic Google Scholar P Specht, P Specht Department of MSE, University of California Berkeley, Berkeley, CA 94720, USA Search for other works by this author on: Oxford Academic Google Scholar B Freitag, B Freitag Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, The Netherlands Search for other works by this author on: Oxford Academic Google Scholar ER Kieft, ER Kieft Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, The Netherlands Search for other works by this author on: Oxford Academic Google Scholar S Rozeveld, S Rozeveld The Dow Chemical Company, Midland, MI 48667, USA Search for other works by this author on: Oxford Academic Google Scholar J Kang, J Kang The Dow Chemical Company, Midland, MI 48667, USA Search for other works by this author on: Oxford Academic Google Scholar AJ Fielitz, AJ Fielitz The Dow Chemical Company, Midland, MI 48667, USA Search for other works by this author on: Oxford Academic Google Scholar TR Fielitz, TR Fielitz The Dow Chemical Company, Midland, MI 48667, USA Search for other works by this author on: Oxford Academic Google Scholar DF Yancey, DF Yancey The Dow Chemical Company, Midland, MI 48667, USA Search for other works by this author on: Oxford Academic Google Scholar D van Dyck D van Dyck EMAT, University of Antwerp, 2020 Antwerp, Belgium Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 28, Issue S1, 1 August 2022, Pages 2762–2763, https://doi.org/10.1017/S143192762201039X Published: 01 August 2022

Technological opportunities are explored to enhance detection schemes in transmission electron microscopy (TEM) that build on the detection of single-electron scattering events across the typical spectrum of interdisciplinary applications. They range from imaging with high spatiotemporal resolution to diffraction experiments at the window to quantum mechanics, where the wave-particle dualism of single electrons is evident. At the ultimate detection limit, where isolated electrons are delivered to interact with solids, we find that the beam current dominates damage processes instead of the deposited electron charge, which can be exploited to modify electron beam-induced sample alterations. The results are explained by assuming that all electron scattering are inelastic and include phonon excitation that can hardly be distinguished from elastic electron scattering. Consequently, a coherence length and a related coherence time exist that reflect the interaction of the electron with the sample and change linearly with energy loss. Phonon excitations are of small energy (<100 meV), but they occur frequently and scale with beam current in the irradiated area, which is why we can detect their contribution to beam-induced sample alterations and damage.

Journal Article The Ultimate Detection Limit: Building Electron Diffraction Patterns One Electron at a Time Get access Christian Kisielowski, Christian Kisielowski The Molecular Foundry and Joint Center for Artificial Photosynthesis, Berkeley, California, United States Search for other works by this author on: Oxford Academic Google Scholar Petra Specht, Petra Specht University of California in Berkeley, Berkeley, California, United States Search for other works by this author on: Oxford Academic Google Scholar David Yancey, David Yancey Dow, Midland, Minnesota, United States Search for other works by this author on: Oxford Academic Google Scholar Steve Rozeveld, Steve Rozeveld Dow, Midland, Minnesota, United States Search for other works by this author on: Oxford Academic Google Scholar Joo Kang, Joo Kang Dow, Midland, Minnesota, United States Search for other works by this author on: Oxford Academic Google Scholar Alyssa McKenna, Alyssa McKenna Dow, Midland, Minnesota, United States Search for other works by this author on: Oxford Academic Google Scholar David Barton David Barton Dow, Midland, Minnesota, 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 2874–2876, https://doi.org/10.1017/S1431927620023065 Published: 01 August 2020

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Stoichiometric gallium oxide sulfide Ga2(O1 − xSx)3 thin-film alloys were synthesized by pulsed-laser deposition with x ≤ 0.35. All deposited Ga2(O1 − xSx)3 films were found to be amorphous. Despite the amorphous structure, the films have a well-defined, room-temperature optical bandgap tunable from 5.0 eV down to 3.0 eV. The optical absorption data are interpreted using a modified valence-band anticrossing model that is applicable for highly mismatched alloys. The model provides a quantitative method to more accurately determine the bandgap as well as an insight into how the band edges are changing with composition. The observed large reduction in energy bandgap with a small sulfur ratio arises from the anticrossing interaction between the valence band of Ga2O3 and the localized sulfur level at 1.0 eV above the Ga2O3 valence-band maximum.

Journal Article Low Dose-Rate High-Resolution Transmission Electron Microscopy of Group III – Nitride Electronic Device Structures Using a Direct Electron Detector Get access P Specht, P Specht University of California, Berkeley, Dept. of Materials Science & Engineering, Berkeley, CA, USA Search for other works by this author on: Oxford Academic Google Scholar R Kirste, R Kirste NC State University, Dept. of Materials Science & Engineering, Raleigh, NC, USA Search for other works by this author on: Oxford Academic Google Scholar Z Sitar, Z Sitar NC State University, Dept. of Materials Science & Engineering, Raleigh, NC, USA Search for other works by this author on: Oxford Academic Google Scholar C Kisielowski C Kisielowski Lawrence Berkeley National Laboratory, Molecular Foundry, Berkeley, CA, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 25, Issue S2, 1 August 2019, Pages 1714–1715, https://doi.org/10.1017/S1431927619009309 Published: 01 August 2019

A combination of atomic resolution phase contrast electron microscopy and pulsed electron beams reveals pristine properties of MgCl2 at 1.7 Å resolution that were previously masked by air and beam damage. Both the inter‐ and intra‐layer bonding in pristine MgCl2 are weak, which leads to uncommonly large local orientation variations that characterize this Ziegler–Natta catalyst support. By delivering electrons with 1–10 ps pulses and ≈160 ps delay times, phonons induced by the electron irradiation in the material are allowed to dissipate before the subsequent delivery of the next electron packet, thus mitigating phonon accumulations. As a result, the total electron dose can be extended by a factor of 80–100 to study genuine material properties at atomic resolution without causing object alterations, which is more effective than reducing the sample temperature. In conditions of minimal damage, beam currents approach femtoamperes with dose rates around 1 eÅ−2 s−1. Generally, the utilization of pulsed electron beams is introduced herein to access genuine material properties while minimizing beam damage.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The recent availability of high quality bulk GaN substrates with low threading dislocation density has made vertical power device structures an attractive possibility. Due to the low probability of a threading dislocation occurring within the active area of devices grown upon bulk GaN, reliability is driven by bulk or surface effects. Past work upon the reliability of Ni-GaN Schottky interfaces has suggested that interdiffusion of the Ni into the GaN can occur under thermal stress, adversely affecting the effective energy height of the barrier and increasing the ohmic nature of the interface. Conditions similar to such thermal stressing can be found at typical operating points in high current power devices used in power electronic applications. Our work examines the influence of high current density stress upon the reliability of vertical bulk GaN Schottky diodes. The vertical diodes studied were fabricated with Pd Schottky metallization with an Au ohmic overlayer. To study the effects of surface chemistry, reliability is compared between devices fabricated with different acidic and basic surface preparations, using HCl and KOH respectively. The fabricated devices were subject to life testing under varying levels of constant current density, up to 10 kA/cm^2. The lifetesting system was designed as a stress-measure-stress system, allowing for the evaluation of device parameters in-situ during testing. Electrical parameters indicating the state of the Schottky barrier were evaluated continuously during the measurement points of testing. In addition, a measurement of barrier inhomogeneity, evaluated using the Tung model, was also used as an indication of the condition of the Schottky interface. The microstructure of the interface before and after stress was examined using S/TEM imaging of representative lamellae samples of the stressed and unstressed devices. EDS imaging was used to determine the degree of diffusion between the Schottky metallization and the GaN substrate. Results of microstructure imaging are correlated with the electrical measurements taken to determine the responsible mechanisms for device degradation.