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Rossi AW, Bourgeois MR, Walton C, Masiello DJ. Probing the Polarization of Low-Energy Excitations in 2D Materials from Atomic Crystals to Nanophotonic Arrays Using Momentum-Resolved Electron Energy Loss Spectroscopy. NANO LETTERS 2024; 24:7748-7756. [PMID: 38874581 DOI: 10.1021/acs.nanolett.4c01797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
Spectroscopies utilizing free electron beams as probes offer detailed information on the reciprocal-space excitations of 2D materials such as graphene and transition metal dichalcogenide monolayers. Yet, despite the attention paid to such quantum materials, less consideration has been given to the electron-beam characterization of 2D periodic nanostructures such as photonic crystals, metasurfaces, and plasmon arrays, which can exhibit the same lattice and excitation symmetries as their atomic analogues albeit at drastically different length, momentum, and energy scales. Because of their lack of covalent bonding and influence of retarded electromagnetic interactions, important physical distinctions arise that complicate interpretation of scattering signals. Here we present a fully-retarded theoretical framework for describing the inelastic scattering of wide-field electron beams from 2D materials and apply it to investigate the complementarity in sample excitation information gained in the measurement of a honeycomb plasmon array versus angle-resolved optical spectroscopy in comparison to single monolayer graphene.
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Affiliation(s)
- Andrew W Rossi
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Marc R Bourgeois
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Caleb Walton
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - David J Masiello
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
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2
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Hoglund ER, Walker HA, Hussain K, Bao DL, Ni H, Mamun A, Baxter J, Caldwell JD, Khan A, Pantelides ST, Hopkins PE, Hachtel JA. Nonequivalent Atomic Vibrations at Interfaces in a Polar Superlattice. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024:e2402925. [PMID: 38717326 DOI: 10.1002/adma.202402925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 04/17/2024] [Indexed: 06/15/2024]
Abstract
In heterostructures made from polar materials, e.g., AlN-GaN-AlN, the nonequivalence of the two interfaces is long recognized as a critical aspect of their electronic properties; in that, they host different 2D carrier gases. Interfaces play an important role in the vibrational properties of materials, where interface states enhance thermal conductivity and can generate unique infrared-optical activity. The nonequivalence of the corresponding interface atomic vibrations, however, is not investigated so far due to a lack of experimental techniques with both high spatial and high spectral resolution. Herein, the nonequivalence of AlN-(Al0.65Ga0.35)N and (Al0.65Ga0.35)N-AlN interface vibrations is experimentally demonstrated using monochromated electron energy-loss spectroscopy in the scanning transmission electron microscope (STEM-EELS) and density-functional-theory (DFT) calculations are employed to gain insights in the physical origins of observations. It is demonstrated that STEM-EELS possesses sensitivity to the displacement vector of the vibrational modes as well as the frequency, which is as critical to understanding vibrations as polarization in optical spectroscopies. The combination enables direct mapping of the nonequivalent interface phonons between materials with different phonon polarizations. The results demonstrate the capacity to carefully assess the vibrational properties of complex heterostructures where interface states dominate the functional properties.
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Affiliation(s)
- Eric R Hoglund
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
- Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Harrison A Walker
- Department of Physics and, Astronomy, Vanderbilt University, Nashville, TN, 37235, USA
- Interdisciplinary Materials Science Program, Vanderbilt University, Nashville, TN, 37235, USA
| | - Kamal Hussain
- Department of Electrical Engineering, University of South Carolina, Columbia, SC, 29208, USA
| | - De-Liang Bao
- Department of Physics and, Astronomy, Vanderbilt University, Nashville, TN, 37235, USA
| | - Haoyang Ni
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61820, USA
- Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61820, USA
| | - Abdullah Mamun
- Interdisciplinary Materials Science Program, Vanderbilt University, Nashville, TN, 37235, USA
| | - Jefferey Baxter
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
| | - Joshua D Caldwell
- Department of Mechanical Engineering and Electrical Engineering, Vanderbilt University, Nashville, TN, 37235, USA
| | - Asif Khan
- Department of Electrical Engineering, University of South Carolina, Columbia, SC, 29208, USA
| | - Sokrates T Pantelides
- Department of Physics and, Astronomy, Vanderbilt University, Nashville, TN, 37235, USA
- Interdisciplinary Materials Science Program, Vanderbilt University, Nashville, TN, 37235, USA
- Department of Electrical and Computer Engineering, Vanderbilt University, Nashville, TN, 37235, USA
| | - Patrick E Hopkins
- Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, 22904, USA
- Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, 22904, USA
- Department of Physics, University of Virginia, Charlottesville, VA, 22904, USA
| | - Jordan A Hachtel
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37830, USA
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3
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Moradifar P, Liu Y, Shi J, Siukola Thurston ML, Utzat H, van Driel TB, Lindenberg AM, Dionne JA. Accelerating Quantum Materials Development with Advances in Transmission Electron Microscopy. Chem Rev 2023. [PMID: 37979189 DOI: 10.1021/acs.chemrev.2c00917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2023]
Abstract
Quantum materials are driving a technology revolution in sensing, communication, and computing, while simultaneously testing many core theories of the past century. Materials such as topological insulators, complex oxides, superconductors, quantum dots, color center-hosting semiconductors, and other types of strongly correlated materials can exhibit exotic properties such as edge conductivity, multiferroicity, magnetoresistance, superconductivity, single photon emission, and optical-spin locking. These emergent properties arise and depend strongly on the material's detailed atomic-scale structure, including atomic defects, dopants, and lattice stacking. In this review, we describe how progress in the field of electron microscopy (EM), including in situ and in operando EM, can accelerate advances in quantum materials and quantum excitations. We begin by describing fundamental EM principles and operation modes. We then discuss various EM methods such as (i) EM spectroscopies, including electron energy loss spectroscopy (EELS), cathodoluminescence (CL), and electron energy gain spectroscopy (EEGS); (ii) four-dimensional scanning transmission electron microscopy (4D-STEM); (iii) dynamic and ultrafast EM (UEM); (iv) complementary ultrafast spectroscopies (UED, XFEL); and (v) atomic electron tomography (AET). We describe how these methods could inform structure-function relations in quantum materials down to the picometer scale and femtosecond time resolution, and how they enable precision positioning of atomic defects and high-resolution manipulation of quantum materials. For each method, we also describe existing limitations to solve open quantum mechanical questions, and how they might be addressed to accelerate progress. Among numerous notable results, our review highlights how EM is enabling identification of the 3D structure of quantum defects; measuring reversible and metastable dynamics of quantum excitations; mapping exciton states and single photon emission; measuring nanoscale thermal transport and coupled excitation dynamics; and measuring the internal electric field and charge density distribution of quantum heterointerfaces- all at the quantum materials' intrinsic atomic and near atomic-length scale. We conclude by describing open challenges for the future, including achieving stable sample holders for ultralow temperature (below 10K) atomic-scale spatial resolution, stable spectrometers that enable meV energy resolution, and high-resolution, dynamic mapping of magnetic and spin fields. With atomic manipulation and ultrafast characterization enabled by EM, quantum materials will be poised to integrate into many of the sustainable and energy-efficient technologies needed for the 21st century.
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Affiliation(s)
- Parivash Moradifar
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
| | - Yin Liu
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Jiaojian Shi
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road MS69, Menlo Park, California 94025, United States
| | | | - Hendrik Utzat
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Department of Chemistry, University of California Berkeley, Berkeley, California 94720, United States
| | - Tim B van Driel
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Aaron M Lindenberg
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- SLAC National Accelerator Laboratory, 2575 Sand Hill Road MS69, Menlo Park, California 94025, United States
| | - Jennifer A Dionne
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States
- Department of Radiology, Stanford University, Stanford, California 94305, United States
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4
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Wu M, Shi R, Qi R, Li Y, Du J, Gao P. Four-dimensional electron energy-loss spectroscopy. Ultramicroscopy 2023; 253:113818. [PMID: 37544270 DOI: 10.1016/j.ultramic.2023.113818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 06/20/2023] [Accepted: 07/25/2023] [Indexed: 08/08/2023]
Abstract
Recent advances in scanning transmission electron microscopy have enabled atomic-scale focused, coherent, and monochromatic electron probes, achieving nanoscale spatial resolution, meV energy resolution, sufficient momentum resolution, and a wide energy detection range in electron energy-loss spectroscopy (EELS). A four-dimensional EELS (4D-EELS) dataset can be recorded with a slot aperture selecting the specific momentum direction in the diffraction plane and the beam scanning in two spatial dimensions. In this paper, the basic principle of the 4D-EELS technique and a few examples of its application are presented. In addition to parallelly acquired dispersion with energy down to a lattice vibration scale, it can map the real space variation of any EELS spectrum features with a specific momentum transfer and energy loss to study various locally inhomogeneous scattering processes. Furthermore, simple mathematical combinations associating the spectra at different momenta are feasible from the 4D dataset, e.g., the efficient acquisition of a reliable electron magnetic circular dichroism (EMCD) signal is demonstrated. This 4D-EELS technique provides new opportunities to probe the local dispersion and related physical properties at the nanoscale.
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Affiliation(s)
- Mei Wu
- International Center for Quantum Materials, Peking University, Beijing 100871, China; Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Ruochen Shi
- International Center for Quantum Materials, Peking University, Beijing 100871, China; Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Ruishi Qi
- Department of Physics, University of California at Berkeley, Berkeley 94720, United States
| | - Yuehui Li
- International Center for Quantum Materials, Peking University, Beijing 100871, China; Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Jinlong Du
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Peng Gao
- International Center for Quantum Materials, Peking University, Beijing 100871, China; Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China; Collaborative Innovation Center of Quantum Matter, Beijing 100871, China; Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, Beijing 100871, China.
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5
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Yannai M, Adiv Y, Dahan R, Wang K, Gorlach A, Rivera N, Fishman T, Krüger M, Kaminer I. Lossless Monochromator in an Ultrafast Electron Microscope Using Near-Field THz Radiation. PHYSICAL REVIEW LETTERS 2023; 131:145002. [PMID: 37862634 DOI: 10.1103/physrevlett.131.145002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 07/03/2023] [Accepted: 08/21/2023] [Indexed: 10/22/2023]
Abstract
The ability to form monoenergetic electron beams is vital for high-resolution electron spectroscopy and imaging. Such capabilities are commonly achieved using an electron monochromator, which energy filters a dispersed electron beam, thus reducing the electron flux to yield down to meV energy resolution. This reduction in flux hinders the use of monochromators in many applications, such as ultrafast transmission electron microscopes (UTEMs). Here, we develop and demonstrate a mechanism for electron energy monochromation that does not reduce the flux-a lossless monochromator. The mechanism is based on the interaction of free-electron pulses with single-cycle THz near fields, created by nonlinear conversion of an optical laser pulse near the electron beam path inside a UTEM. Our experiment reduces the electron energy spread by a factor of up to 2.9 without compromising the beam flux. Moreover, as the electron-THz interaction takes place over an extended region of many tens of microns in free space, the realized technique is highly robust-granting uniform monochromation over a wide area, larger than the electron beam diameter. We further demonstrate the wide tunability of our method by monochromating the electron beam at multiple primary electron energies from 60 to 200 keV, studying the effect of various electron and THz parameters on its performance. Our findings have direct applications in the fast-growing field of ultrafast electron microscopy, allowing time- and energy-resolved studies of exciton physics, phononic vibrational resonances, charge transport effects, and optical excitations in the mid IR to the far IR.
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Affiliation(s)
- Michael Yannai
- Faculty of Electrical & Computer Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel
- Solid State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Yuval Adiv
- Faculty of Electrical & Computer Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel
- Solid State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Raphael Dahan
- Faculty of Electrical & Computer Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel
- Solid State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Kangpeng Wang
- Faculty of Electrical & Computer Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel
- Solid State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel
- Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201815, China
| | - Alexey Gorlach
- Faculty of Electrical & Computer Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel
- Solid State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Nicholas Rivera
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Tal Fishman
- Faculty of Electrical & Computer Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel
- Solid State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Michael Krüger
- Solid State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel
- Department of Physics, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Ido Kaminer
- Faculty of Electrical & Computer Engineering, Technion - Israel Institute of Technology, Haifa 3200003, Israel
- Solid State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel
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6
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Guo Y, Lupini AR. Automatic and Quantitative Measurement of Spectrometer Aberrations. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2023; 29:1671-1681. [PMID: 37670369 DOI: 10.1093/micmic/ozad084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 06/16/2023] [Accepted: 07/29/2023] [Indexed: 09/07/2023]
Abstract
The performance of electron energy loss spectrometers can often be limited by their electron optical aberrations. Due to recent developments in high energy resolution and momentum-resolved electron energy loss spectroscopy (EELS), there is renewed interest in optimizing the performance of such spectrometers. For example, the "ω - q" mode of momentum-resolved EELS, which uses a small convergence angle and requires aligning diffraction spots with the slot aperture, presents a challenge in the realignments of the spectrometer required by the adjustment of the projection lenses. Automated and robust alignment can greatly benefit such a process. The first step toward this goal is automatic and quantitative measurement of spectrometer aberrations. We demonstrate the measurement of geometric aberrations and distortions in EELS within a monochromated scanning transmission electron microscope (STEM). To better understand the results, we present a wave mechanical simulation of the experiment. Using the measured aberration and distortion coefficients as inputs to the simulation, we find a good match between the simulation and experiment, verifying formulae used in the simulation. From verified simulations with known aberration coefficients, we can assess the accuracy of measurements. Understanding the errors and inaccuracies in the procedure can guide further progress in aberration measurement and correction for new spectrometer developments.
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Affiliation(s)
- Yueming Guo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Andrew R Lupini
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
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7
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Xu M, Bao DL, Li A, Gao M, Meng D, Li A, Du S, Su G, Pennycook SJ, Pantelides ST, Zhou W. Single-atom Vibrational Spectroscopy with Chemical Bonding Sensitivity. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2023; 29:616-617. [PMID: 37613043 DOI: 10.1093/micmic/ozad067.299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Affiliation(s)
- Mingquan Xu
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - De-Liang Bao
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
- Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Aowen Li
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Meng Gao
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Dongqian Meng
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Ang Li
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Shixuan Du
- Institute of Physics, Chinese Academy of Sciences, Beijing, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Gang Su
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
- Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Stephen J Pennycook
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Sokrates T Pantelides
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
- Department of Electrical and Computer Engineering, Vanderbilt University, Nashville, TN, USA
| | - Wu Zhou
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China
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8
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Xu M, Bao DL, Li A, Gao M, Meng D, Li A, Du S, Su G, Pennycook SJ, Pantelides ST, Zhou W. Single-atom vibrational spectroscopy with chemical-bonding sensitivity. NATURE MATERIALS 2023; 22:612-618. [PMID: 36928385 DOI: 10.1038/s41563-023-01500-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 02/06/2023] [Indexed: 05/05/2023]
Abstract
Correlation of lattice vibrational properties with local atomic configurations in materials is essential for elucidating functionalities that involve phonon transport in solids. Recent developments in vibrational spectroscopy in a scanning transmission electron microscope have enabled direct measurements of local phonon modes at defects and interfaces by combining high spatial and energy resolution. However, pushing the ultimate limit of vibrational spectroscopy in a scanning transmission electron microscope to reveal the impact of chemical bonding on local phonon modes requires extreme sensitivity of the experiment at the chemical-bond level. Here we demonstrate that, with improved instrument stability and sensitivity, the specific vibrational signals of the same substitutional impurity and the neighbouring carbon atoms in monolayer graphene with different chemical-bonding configurations are clearly resolved, complementary with density functional theory calculations. The present work opens the door to the direct observation of local phonon modes with chemical-bonding sensitivity, and provides more insights into the defect-induced physics in graphene.
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Affiliation(s)
- Mingquan Xu
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, P. R. China
| | - De-Liang Bao
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
| | - Aowen Li
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Meng Gao
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Dongqian Meng
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Ang Li
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Shixuan Du
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, P. R. China
- Institute of Physics, Chinese Academy of Sciences, Beijing, P. R. China
| | - Gang Su
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, P. R. China
- Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Stephen J Pennycook
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, P. R. China
| | - Sokrates T Pantelides
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, P. R. China.
- Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA.
- Department of Electrical and Computer Engineering, Vanderbilt University, Nashville, TN, USA.
| | - Wu Zhou
- School of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, P. R. China.
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9
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Li N, Shi R, Li Y, Qi R, Liu F, Zhang X, Liu Z, Li Y, Guo X, Liu K, Jiang Y, Li XZ, Chen J, Liu L, Wang EG, Gao P. Phonon transition across an isotopic interface. Nat Commun 2023; 14:2382. [PMID: 37185918 PMCID: PMC10130007 DOI: 10.1038/s41467-023-38053-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2022] [Accepted: 04/13/2023] [Indexed: 05/17/2023] Open
Abstract
Isotopic mixtures result in distinct properties of materials such as thermal conductivity and nuclear process. However, the knowledge of isotopic interface remains largely unexplored mainly due to the challenges in atomic-scale isotopic identification. Here, using electron energy-loss spectroscopy in a scanning transmission electron microscope, we reveal momentum-transfer-dependent phonon behavior at the h-10BN/h-11BN isotope heterostructure with sub-unit-cell resolution. We find the phonons' energy changes gradually across the interface, featuring a wide transition regime. Phonons near the Brillouin zone center have a transition regime of ~3.34 nm, whereas phonons at the Brillouin zone boundary have a transition regime of ~1.66 nm. We propose that the isotope-induced charge effect at the interface accounts for the distinct delocalization behavior. Moreover, the variation of phonon energy between atom layers near the interface depends on both of momentum transfer and mass change. This study provides new insights into the isotopic effects in natural materials.
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Affiliation(s)
- Ning Li
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China
- Electron Microscopy Laboratory, School of Physics, Peking University, 100871, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China
| | - Ruochen Shi
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China
- Electron Microscopy Laboratory, School of Physics, Peking University, 100871, Beijing, China
| | - Yifei Li
- School of Materials Science and Engineering, Peking University, 100871, Beijing, China
| | - Ruishi Qi
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China
- Electron Microscopy Laboratory, School of Physics, Peking University, 100871, Beijing, China
- Department of Physics, University of California at Berkeley, Berkeley, CA, 94720, USA
| | - Fachen Liu
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China
- Electron Microscopy Laboratory, School of Physics, Peking University, 100871, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China
| | - Xiaowen Zhang
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China
- Electron Microscopy Laboratory, School of Physics, Peking University, 100871, Beijing, China
| | - Zhetong Liu
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China
- Electron Microscopy Laboratory, School of Physics, Peking University, 100871, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, 100871, Beijing, China
| | - Yuehui Li
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China
- Electron Microscopy Laboratory, School of Physics, Peking University, 100871, Beijing, China
| | - Xiangdong Guo
- CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, 100190, Beijing, China
| | - Kaihui Liu
- Institute of Condensed Matter and Material Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
- Collaborative Innovation Center of Quantum Matter, 100871, Beijing, China
| | - Ying Jiang
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China
- Collaborative Innovation Center of Quantum Matter, 100871, Beijing, China
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, 100871, Beijing, China
| | - Xin-Zheng Li
- Institute of Condensed Matter and Material Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, 100871, Beijing, China
- State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Peking University, 100871, Beijing, China
| | - Ji Chen
- Institute of Condensed Matter and Material Physics, Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, 100871, Beijing, China.
- Collaborative Innovation Center of Quantum Matter, 100871, Beijing, China.
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, 100871, Beijing, China.
| | - Lei Liu
- School of Materials Science and Engineering, Peking University, 100871, Beijing, China.
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, 100871, Beijing, China.
| | - En-Ge Wang
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China.
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, 100871, Beijing, China.
- Songshan Lake Materials Laboratory, 523808, Dongguan, China.
- School of Physics, Shanghai University, 200444, Shanghai, China.
| | - Peng Gao
- International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China.
- Electron Microscopy Laboratory, School of Physics, Peking University, 100871, Beijing, China.
- Collaborative Innovation Center of Quantum Matter, 100871, Beijing, China.
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, 100871, Beijing, China.
- Hefei National Laboratory, 230088, Hefei, China.
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10
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Howie A. A brief peek at the cyclotron in our microscope. Ultramicroscopy 2023; 248:113717. [PMID: 36940585 DOI: 10.1016/j.ultramic.2023.113717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 02/25/2023] [Accepted: 03/10/2023] [Indexed: 03/13/2023]
Abstract
The influence of low energy bremsstrahlung emission on the performance of electron spectrometers and monochromators is investigated. Despite the occurrence of multi-photon events, the effect of the main azimuthal (organ pipe) mode is likely to be negligible. Potentially more serious is a new radial mode not considered in the classical theory but revealed in the quantum mechanics picture. The progress of the finely focused wave at the spectrometer entrance slit is described by a coherent wave packet of many oscillator states. It is shielded from disruption by a relatively much longer half-life. Cavity effects causing additional suppression of bremsstrahlung emission are briefly discussed.
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Affiliation(s)
- A Howie
- Department of Physics, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, UK.
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11
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Du J, Chen JH, Li Y, Shi R, Wu M, Xiao YF, Gao P. Electron Microscopy Probing Electron-Photon Interactions in SiC Nanowires with Ultrawide Energy and Momentum Match. NANO LETTERS 2022; 22:6207-6214. [PMID: 35905393 DOI: 10.1021/acs.nanolett.2c01672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Light-matter interactions are commonly probed by optical spectroscopy, which, however, has some fundamental limitations such as diffraction-limited spatial resolution, tiny momentum transfer, and noncontinuous excitation/detection. In this work, through the use of scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) with ultrawide energy and momentum match and subnanometer spatial resolution, the longitudinal Fabry-Perot (FP) resonating modes and the transverse whispering-gallery modes (WGMs) in individual SiC nanowires are simultaneously excited and detected, which span from near-infrared (∼1.2 μm) to ultraviolet (∼0.2 μm) spectral regime, and the momentum transfer can range up to 108 cm-1. The size effects on the resonant spectra of nanowires are also revealed. This work provides an alternative technique to optical resonating spectroscopy and light-matter interactions in dielectric nanostructures, which is promising for modulating free electrons via photonic structures.
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Affiliation(s)
- Jinlong Du
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing100871, China
| | - Jin-Hui Chen
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing100871, China
- Institute of Electromagnetics and Acoustics, Xiamen University, Xiamen361005, China
| | - Yuehui Li
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing100871, China
- International Center for Quantum Materials, Peking University, Beijing100871, China
| | - Ruochen Shi
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing100871, China
- International Center for Quantum Materials, Peking University, Beijing100871, China
| | - Mei Wu
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing100871, China
- International Center for Quantum Materials, Peking University, Beijing100871, China
| | - Yun-Feng Xiao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing100871, China
| | - Peng Gao
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing100871, China
- International Center for Quantum Materials, Peking University, Beijing100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing100871, China
- Interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials, Peking University, Beijing100871, China
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12
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Mendis BG. Quantum theory of magnon excitation by high energy electron beams. Ultramicroscopy 2022; 239:113548. [DOI: 10.1016/j.ultramic.2022.113548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 04/25/2022] [Accepted: 05/04/2022] [Indexed: 10/18/2022]
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13
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Ko W, Gai Z, Puretzky AA, Liang L, Berlijn T, Hachtel JA, Xiao K, Ganesh P, Yoon M, Li AP. Understanding Heterogeneities in Quantum Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022:e2106909. [PMID: 35170112 DOI: 10.1002/adma.202106909] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 02/08/2022] [Indexed: 06/14/2023]
Abstract
Quantum materials are usually heterogeneous, with structural defects, impurities, surfaces, edges, interfaces, and disorder. These heterogeneities are sometimes viewed as liabilities within conventional systems; however, their electronic and magnetic structures often define and affect the quantum phenomena such as coherence, interaction, entanglement, and topological effects in the host system. Therefore, a critical need is to understand the roles of heterogeneities in order to endow materials with new quantum functions for energy and quantum information science applications. In this article, several representative examples are reviewed on the recent progress in connecting the heterogeneities to the quantum behaviors of real materials. Specifically, three intertwined topic areas are assessed: i) Reveal the structural, electronic, magnetic, vibrational, and optical degrees of freedom of heterogeneities. ii) Understand the effect of heterogeneities on the behaviors of quantum states in host material systems. iii) Control heterogeneities for new quantum functions. This progress is achieved by establishing the atomistic-level structure-property relationships associated with heterogeneities in quantum materials. The understanding of the interactions between electronic, magnetic, photonic, and vibrational states of heterogeneities enables the design of new quantum materials, including topological matter and quantum light emitters based on heterogenous 2D materials.
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Affiliation(s)
- Wonhee Ko
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Zheng Gai
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Alexander A Puretzky
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Liangbo Liang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Tom Berlijn
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Jordan A Hachtel
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Kai Xiao
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Panchapakesan Ganesh
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - Mina Yoon
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
| | - An-Ping Li
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831, USA
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14
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OUP accepted manuscript. Microscopy (Oxf) 2022; 71:i174-i199. [DOI: 10.1093/jmicro/dfab050] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 11/20/2021] [Accepted: 01/28/2022] [Indexed: 11/14/2022] Open
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16
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Abstract
The breakdown of translational symmetry at heterointerfaces leads to the emergence of new phonon modes localized at the interface1. These modes have an essential role in thermal and electrical transport properties in devices, especially in miniature ones wherein the interface may dominate the entire response of the device2. Although related theoretical work began decades ago1,3-5, experimental research is totally absent owing to challenges in achieving the combined spatial, momentum and spectral resolutions required to probe localized modes. Here, using the four-dimensional electron energy-loss spectroscopy technique, we directly measure both the local vibrational spectra and the interface phonon dispersion relation for an epitaxial cubic boron nitride/diamond heterointerface. In addition to bulk phonon modes, we observe modes localized at the interface and modes isolated from the interface. These features appear only within approximately one nanometre around the interface. The localized modes observed here are predicted to substantially affect the interface thermal conductance and electron mobility. Our findings provide insights into lattice dynamics at heterointerfaces, and the demonstrated experimental technique should be useful in thermal management, electrical engineering and topological phononics.
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17
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Xie L, He D, He J. SnSe, the rising star thermoelectric material: a new paradigm in atomic blocks, building intriguing physical properties. MATERIALS HORIZONS 2021; 8:1847-1865. [PMID: 34846469 DOI: 10.1039/d1mh00091h] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Thermoelectric (TE) materials, which enable direct energy conversion between waste heat and electricity, have witnessed enormous and exciting developments over last several decades due to innovative breakthroughs both in materials and the synergistic optimization of structures and properties. Among the promising state-of-the-art materials for next-generation thermoelectrics, tin selenide (SnSe) has attracted rapidly growing research interest for its high TE performance and the intrinsic layered structure that leads to strong anisotropy. Moreover, complex interactions between lattice, charge, and orbital degrees of freedom in SnSe make up a large phase space for the optimization of its TE properties via the simultaneous tuning of structural and chemical features. Various techniques, especially advanced electron microscopy (AEM), have been devoted to exploring these critical multidiscipline correlations between TE properties and microstructures. In this review, we first focus on the intrinsic layered structure as well as the extrinsic structural "imperfectness" of various dimensions in SnSe as studied by AEM. Based on these characterization results, we give a comprehensive discussion on the current understanding of the structure-property relationship. We then point out the challenges and opportunities as provided by modern AEM techniques toward a deeper knowledge of SnSe based on electronic structures and lattice dynamics at the nanometer or even atomic scale, for example, the measurements of local charge and electric field distribution, phonon vibrations, bandgap, valence state, temperature, and resultant TE effects.
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Affiliation(s)
- Lin Xie
- Shenzhen Key Laboratory of Thermoelectric Materials and Department of Physics, Southern University of Science and Technology, Shenzhen, 518055, China.
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18
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Venkatraman K, Crozier PA. Role of Convergence and Collection Angles in the Excitation of Long- and Short-Wavelength Phonons with Vibrational Electron Energy-Loss Spectroscopy. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2021; 27:1-9. [PMID: 34172104 DOI: 10.1017/s1431927621012034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Current generation electron monochromators employed as attachments to scanning transmission electron microscopes (STEM) offer the ability to obtain vibrational information from materials using electron energy-loss spectroscopy (EELS). We show here that in crystals, long- and short-wavelength phonon modes can be probed simultaneously with on-axis vibrational STEM EELS. The long-wavelength phonons are probed via dipole scattering, while the short-wavelength modes are probed via impact scattering of the incident electrons. The localized character of the short-wavelength modes is demonstrated by scanning the electron beam across the edge of a hexagonal boron nitride nanoparticle. It is found that employing convergence angles that encompass multiple Brillouin zone boundaries enhances the short-wavelength phonon contribution to the vibrational energy-loss spectrum much more than that achieved by employing collection angles that encompass multiple Brillouin zone boundaries. Probing short-wavelength phonons at high spatial resolution with on-axis vibrational STEM EELS will help develop a fundamental connection between vibrational excitations and bonding arrangements at atomic-scale heterogeneities in materials.
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Affiliation(s)
- Kartik Venkatraman
- School for the Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ85287, USA
| | - Peter A Crozier
- School for the Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ85287, USA
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19
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Konečná A, Iyikanat F, García de Abajo FJ. Theory of Atomic-Scale Vibrational Mapping and Isotope Identification with Electron Beams. ACS NANO 2021; 15:9890-9899. [PMID: 34006088 DOI: 10.1021/acsnano.1c01071] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Transmission electron microscopy and spectroscopy currently enable the acquisition of spatially resolved spectral information from a specimen by focusing electron beams down to a sub-angstrom spot and then analyzing the energy of the inelastically scattered electrons with few-meV energy resolution. This technique has recently been used to experimentally resolve vibrational modes in 2D materials emerging at mid-infrared frequencies. Here, on the basis of first-principles theory, we demonstrate the possibility of identifying single isotope atom impurities in a nanostructure through the trace that they leave in the spectral and spatial characteristics of the vibrational modes. Specifically, we examine a hexagonal boron nitride molecule as an example of application, in which the presence of a single isotope impurity is revealed through changes in the electron spectra, as well as in the space-, energy-, and momentum-resolved inelastic electron signal. We compare these results with conventional far-field spectroscopy, showing that electron beams offer superior spatial resolution combined with the ability to probe the complete set of vibrational modes, including those that are optically dark. Our study is relevant for the atomic-scale characterization of vibrational modes in materials of interest, including a detailed mapping of isotope distributions.
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Affiliation(s)
- Andrea Konečná
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona, Spain
| | - Fadil Iyikanat
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona, Spain
| | - F Javier García de Abajo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Spain
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20
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Qi R, Li N, Du J, Shi R, Huang Y, Yang X, Liu L, Xu Z, Dai Q, Yu D, Gao P. Four-dimensional vibrational spectroscopy for nanoscale mapping of phonon dispersion in BN nanotubes. Nat Commun 2021; 12:1179. [PMID: 33608559 PMCID: PMC7896073 DOI: 10.1038/s41467-021-21452-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 01/26/2021] [Indexed: 11/17/2022] Open
Abstract
Directly mapping local phonon dispersion in individual nanostructures can advance our understanding of their thermal, optical, and mechanical properties. However, this requires high detection sensitivity and combined spatial, energy and momentum resolutions, thus has been elusive. Here, we demonstrate a four-dimensional electron energy loss spectroscopy technique, and present position-dependent phonon dispersion measurements in individual boron nitride nanotubes. By scanning the electron beam in real space while monitoring both the energy loss and the momentum transfer, we are able to reveal position- and momentum-dependent lattice vibrations at nanometer scale. Our measurements show that the phonon dispersion of multi-walled nanotubes is locally close to hexagonal-boron nitride crystals. Interestingly, acoustic phonons are sensitive to defect scattering, while optical modes are insensitive to small voids. This work not only provides insights into vibrational properties of boron nitride nanotubes, but also demonstrates potential of the developed technique in nanoscale phonon dispersion measurements.
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Affiliation(s)
- Ruishi Qi
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, China
- International Center for Quantum Materials, Peking University, Beijing, China
- Department of Physics, University of California at Berkeley, Berkeley, CA, USA
| | - Ning Li
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, China
- International Center for Quantum Materials, Peking University, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Jinlong Du
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, China
| | - Ruochen Shi
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, China
- International Center for Quantum Materials, Peking University, Beijing, China
| | - Yang Huang
- School of Materials Science and Engineering, Hebei University of Technology, Tianjin, China
- Hebei Key Laboratory of Boron Nitride Micro and Nano Materials, Hebei University of Technology, Tianjin, China
| | - Xiaoxia Yang
- CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, China
| | - Lei Liu
- School of Materials Science and Engineering, Peking University, Beijing, China
| | - Zhi Xu
- Songshan Lake Materials Lab, Institute of Physics, Chinese Academy of Sciences, Guangdong, China
| | - Qing Dai
- CAS Key Laboratory of Nanophotonic Materials and Devices, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, China
| | - Dapeng Yu
- Shenzhen Key Laboratory of Quantum Science and Engineering, Shenzhen, China
| | - Peng Gao
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, China.
- International Center for Quantum Materials, Peking University, Beijing, China.
- Collaborative Innovation Center of Quantum Matter, and Beijing Key Laboratory of Quantum Devices, Beijing, China.
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21
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Yan X, Liu C, Gadre CA, Gu L, Aoki T, Lovejoy TC, Dellby N, Krivanek OL, Schlom DG, Wu R, Pan X. Single-defect phonons imaged by electron microscopy. Nature 2021; 589:65-69. [DOI: 10.1038/s41586-020-03049-y] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Accepted: 10/07/2020] [Indexed: 11/09/2022]
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22
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Li N, Guo X, Yang X, Qi R, Qiao T, Li Y, Shi R, Li Y, Liu K, Xu Z, Liu L, García de Abajo FJ, Dai Q, Wang EG, Gao P. Direct observation of highly confined phonon polaritons in suspended monolayer hexagonal boron nitride. NATURE MATERIALS 2021; 20:43-48. [PMID: 32807920 DOI: 10.1038/s41563-020-0763-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 07/09/2020] [Indexed: 05/21/2023]
Abstract
Phonon polaritons enable light confinement at deep subwavelength scales, with potential technological applications, such as subdiffraction imaging, sensing and engineering of spontaneous emission. However, the trade-off between the degree of confinement and the excitation efficiency of phonon polaritons prevents direct observation of these modes in monolayer hexagonal boron nitride (h-BN), where they are expected to reach ultrahigh confinement. Here, we use monochromatic electron energy-loss spectroscopy (about 7.5 meV energy resolution) in a scanning transmission electron microscope to measure phonon polaritons in monolayer h-BN, directly demonstrating the existence of these modes as the phonon Reststrahlen band (RS) disappears. We find phonon polaritons in monolayer h-BN to exhibit high confinement (>487 times smaller wavelength than that of light in free space) and ultraslow group velocity down to about 10-5c. The large momentum compensation provided by electron beams additionally allows us to excite phonon polaritons over nearly the entire RS band of multilayer h-BN. These results open up a broad range of opportunities for the engineering of metasurfaces and strongly enhanced light-matter interactions.
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Affiliation(s)
- Ning Li
- Division of Nanophotonics, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, China
- International Center for Quantum Materials, Peking University, Beijing, China
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
| | - Xiangdong Guo
- Division of Nanophotonics, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing, China
| | - Xiaoxia Yang
- Division of Nanophotonics, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, China.
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China.
| | - Ruishi Qi
- International Center for Quantum Materials, Peking University, Beijing, China
| | - Tianyu Qiao
- International Center for Quantum Materials, Peking University, Beijing, China
| | - Yifei Li
- Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing, China
| | - Ruochen Shi
- International Center for Quantum Materials, Peking University, Beijing, China
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, China
| | - Yuehui Li
- International Center for Quantum Materials, Peking University, Beijing, China
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, China
| | - Kaihui Liu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing, China
- Collaborative Innovation Center of Quantum Matter, Beijing, China
| | - Zhi Xu
- Songshan Lake Materials Laboratory, Institute of Physics, Chinese Academy of Sciences, Dongguan, China
| | - Lei Liu
- Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing, China
| | - F Javier García de Abajo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain
| | - Qing Dai
- Division of Nanophotonics, CAS Key Laboratory of Standardization and Measurement for Nanotechnology, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, China.
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing, China.
| | - En-Ge Wang
- International Center for Quantum Materials, Peking University, Beijing, China
- Collaborative Innovation Center of Quantum Matter, Beijing, China
- Songshan Lake Materials Laboratory, Institute of Physics, Chinese Academy of Sciences, Dongguan, China
- School of Physics, Liaoning University, Shenyang, China
| | - Peng Gao
- International Center for Quantum Materials, Peking University, Beijing, China.
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, China.
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China.
- Collaborative Innovation Center of Quantum Matter, Beijing, China.
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23
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Egerton RF, Venkatraman K, March K, Crozier PA. Properties of Dipole-Mode Vibrational Energy Losses Recorded From a TEM Specimen. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2020; 26:1117-1123. [PMID: 32867870 DOI: 10.1017/s1431927620024423] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The authors discuss the dipole vibrational modes that predominate in the energy-loss spectra of ionic materials below 1 eV, concentrating on thin-film specimens of typical transmission electron microscopy (TEM) thickness. The thickness dependence of the intensity is shown to be a useful guide to the bulk or surface character of vibrational peaks. The lateral and depth resolution of the energy-loss signal is investigated with the aid of finite-element calculations.
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Affiliation(s)
- Ray F Egerton
- Physics Department, University of Alberta, Edmonton, Alberta, CanadaT6G 2E1
| | - Kartik Venkatraman
- School for Engineering of Matter, Transport & Energy, Arizona State University, Tempe, AZ85281, USA
| | - Katia March
- Eyring Materials Center, Arizona State University, Tempe, AZ85281, USA
| | - Peter A Crozier
- School for Engineering of Matter, Transport & Energy, Arizona State University, Tempe, AZ85281, USA
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24
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Rez P, Singh A. Lattice resolution of vibrational modes in the electron microscope. Ultramicroscopy 2020; 220:113162. [PMID: 33189051 DOI: 10.1016/j.ultramic.2020.113162] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 10/28/2020] [Accepted: 11/01/2020] [Indexed: 10/23/2022]
Abstract
The combination of aberration correction and ultra high energy resolution with monochromators has made it possible to record images showing lattice resolution in phonon modes, both with a displaced collection aperture and more recently with an on -axis collection aperture. In practice the objective aperture has to include Bragg reflections that correspond to the observed lattice image spacings, and the specimen has to be sufficiently thick for adequate phonon scattered intensity. There has been controversy as to whether the images with the on axis detector are really a consequence of lattice resolution in a phonon mode or just a transfer of information from an image that was formed by elastically scattered electrons. We present results of calculations based on a theory that includes the possibility of dynamical electron diffraction for both incident and scattered electrons and the full phonon dispersion relation. We show that Umklapp scattering from the second Brillouin Zone back to the first Brillouin Zone is necessary for lattice resolution with the on axis detector and that it is therefore reasonable to attribute the lattice resolution to the phonon scattering.
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Affiliation(s)
- Peter Rez
- Department of Physics, Arizona State University, Tempe, AZ 85287-1504, USA.
| | - Arunima Singh
- Department of Physics, Arizona State University, Tempe, AZ 85287-1504, USA
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25
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Li Y, Qi R, Shi R, Li N, Gao P. Manipulation of surface phonon polaritons in SiC nanorods. Sci Bull (Beijing) 2020; 65:820-826. [PMID: 36659200 DOI: 10.1016/j.scib.2020.02.026] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 01/10/2020] [Accepted: 02/11/2020] [Indexed: 01/21/2023]
Abstract
Surface phonon polaritons (SPhPs) are potentially very attractive for subwavelength control and manipulation of light at the infrared to terahertz wavelengths. Probing their propagation behavior in nanostructures is crucial to guide rational device design. Here, aided by monochromatic scanning transmission electron microscopy-electron energy loss spectroscopy technique, we measure the dispersion relation of SPhPs in individual SiC nanorods and reveal the effects of size and shape. We find that the SPhPs can be modulated by the geometric shape and size of SiC nanorods. The energy of SPhPs shows red-shift with decreasing radius and the surface optical phonon is mainly concentrated on the surface with large radius. Therefore, the fields can be precisely confined in specific positions by varying the size of the nanorod, allowing effective tuning at nanometer scale. The findings of this work are in agreement with dielectric response theory and numerical simulation, and provide novel strategies for manipulating light in polar dielectrics through shape and size control, enabling the design of novel nanoscale phonon-photonic devices.
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Affiliation(s)
- Yuehui Li
- International Center for Quantum Materials, Peking University, Beijing 100871, China; Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Ruishi Qi
- International Center for Quantum Materials, Peking University, Beijing 100871, China; Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Ruochen Shi
- International Center for Quantum Materials, Peking University, Beijing 100871, China; Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Ning Li
- Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
| | - Peng Gao
- International Center for Quantum Materials, Peking University, Beijing 100871, China; Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China; Collaborative Innovation Center of Quantum Matter, Beijing 100871, China.
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26
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Hage FS, Radtke G, Kepaptsoglou DM, Lazzeri M, Ramasse QM. Single-atom vibrational spectroscopy in the scanning transmission electron microscope. Science 2020; 367:1124-1127. [PMID: 32139541 DOI: 10.1126/science.aba1136] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 02/03/2020] [Indexed: 11/02/2022]
Abstract
Single-atom impurities and other atomic-scale defects can notably alter the local vibrational responses of solids and, ultimately, their macroscopic properties. Using high-resolution electron energy-loss spectroscopy in the electron microscope, we show that a single substitutional silicon impurity in graphene induces a characteristic, localized modification of the vibrational response. Extensive ab initio calculations reveal that the measured spectroscopic signature arises from defect-induced pseudo-localized phonon modes-that is, resonant states resulting from the hybridization of the defect modes and the bulk continuum-with energies that can be directly matched to the experiments. This finding realizes the promise of vibrational spectroscopy in the electron microscope with single-atom sensitivity and has broad implications across the fields of physics, chemistry, and materials science.
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Affiliation(s)
- F S Hage
- SuperSTEM Laboratory, SciTech Daresbury Campus, Daresbury WA4 4AD, UK
| | - G Radtke
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, 75005 Paris, France.
| | - D M Kepaptsoglou
- SuperSTEM Laboratory, SciTech Daresbury Campus, Daresbury WA4 4AD, UK.,York Nanocentre and Department of Physics, University of York, Heslington, York YO10 5DD, UK
| | - M Lazzeri
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, 75005 Paris, France
| | - Q M Ramasse
- SuperSTEM Laboratory, SciTech Daresbury Campus, Daresbury WA4 4AD, UK. .,School of Chemical and Process Engineering and School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK
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27
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Zeiger PM, Rusz J. Efficient and Versatile Model for Vibrational STEM-EELS. PHYSICAL REVIEW LETTERS 2020; 124:025501. [PMID: 32004041 DOI: 10.1103/physrevlett.124.025501] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 11/18/2019] [Indexed: 06/10/2023]
Abstract
We introduce a novel method for the simulation of the impact scattering in vibrational scanning transmission electron microscopy electron energy loss spectroscopy simulations. The phonon-loss process is modeled by a combination of molecular dynamics and elastic multislice calculations within a modified frozen phonon approximation. The key idea is thereby to use a so-called δ thermostat in the classical molecular dynamics simulation to generate frequency dependent configurations of the vibrating specimen's atomic structure. The method includes correlated motion of atoms and provides vibrational spectrum images at a cost comparable to standard frozen phonon calculations. We demonstrate good agreement of our method with simulations and experiments for a 15 nm flake of hexagonal boron nitride.
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Affiliation(s)
- Paul M Zeiger
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, Uppsala 75120, Sweden
| | - Ján Rusz
- Department of Physics and Astronomy, Uppsala University, P.O. Box 516, Uppsala 75120, Sweden
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28
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Zachman MJ, Hachtel JA, Idrobo JC, Chi M. Emerging Electron Microscopy Techniques for Probing Functional Interfaces in Energy Materials. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201902993] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Michael J. Zachman
- Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Jordan A. Hachtel
- Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Juan Carlos Idrobo
- Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Miaofang Chi
- Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37831 USA
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29
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Zachman MJ, Hachtel JA, Idrobo JC, Chi M. Emerging Electron Microscopy Techniques for Probing Functional Interfaces in Energy Materials. Angew Chem Int Ed Engl 2019; 59:1384-1396. [PMID: 31081976 DOI: 10.1002/anie.201902993] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2019] [Revised: 05/01/2019] [Indexed: 11/10/2022]
Abstract
Interfaces play a fundamental role in many areas of chemistry. However, their localized nature requires characterization techniques with high spatial resolution in order to fully understand their structure and properties. State-of-the-art atomic resolution or in situ scanning transmission electron microscopy and electron energy-loss spectroscopy are indispensable tools for characterizing the local structure and chemistry of materials with single-atom resolution, but they are not able to measure many properties that dictate function, such as vibrational modes or charge transfer, and are limited to room-temperature samples containing no liquids. Here, we outline emerging electron microscopy techniques that are allowing these limitations to be overcome and highlight several recent studies that were enabled by these techniques. We then provide a vision for how these techniques can be paired with each other and with in situ methods to deliver new insights into the static and dynamic behavior of functional interfaces.
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Affiliation(s)
- Michael J Zachman
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Jordan A Hachtel
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Juan Carlos Idrobo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Miaofang Chi
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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30
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Yan X, Liu C, Gadre CA, Dai S, Gu L, Yu K, Aoki T, Wu R, Pan X. Unexpected Strong Thermally Induced Phonon Energy Shift for Mapping Local Temperature. NANO LETTERS 2019; 19:7494-7502. [PMID: 31517496 DOI: 10.1021/acs.nanolett.9b03307] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Measuring temperature in nanoscale is crucial for the research and development of microelectronic devices. Plasmon resonance has been utilized to map local temperature gradient in metallic materials (Al) due to their large coefficients of thermal expansion. However, most semiconductors (including Si and SiC) possess much smaller coefficients of thermal expansion due to their strong covalent bonding in crystal structure, for which the plasmon-based temperature measurement becomes unreliable. Here, we report an unexpected strong, thermally induced phonon energy shift in SiC by spatially resolved vibrational spectroscopy in transmission electron microscopy with in situ heating, demonstrating that this shift can be applied as a useful tool for measuring nanoscale temperature. When a bulk phonon spectrum is used, the spatial resolution of vibrational spectroscopy can be as high as one nanometer. Molecular dynamics simulations reveal that lattice expansion only contributes a small fraction of phonon energy shift and that vibrant motions away from the bonds are predominate factors. This study gains deeper insight into the understanding of dynamic behaviors of the phonon and provides a new avenue to measure local temperature in nanodevices.
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31
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Position and momentum mapping of vibrations in graphene nanostructures. Nature 2019; 573:247-250. [PMID: 31406319 DOI: 10.1038/s41586-019-1477-8] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 06/03/2019] [Indexed: 11/08/2022]
Abstract
Propagating atomic vibrational waves-phonons-determine important thermal, mechanical, optoelectronic and transport characteristics of materials. Thus a knowledge of phonon dispersion (that is, the dependence of vibrational energy on momentum) is a key part of our understanding and optimization of a material's behaviour. However, the phonon dispersion of a free-standing monolayer of a two-dimensional material such as graphene, and its local variations, have remained elusive for the past decade because of the experimental limitations of vibrational spectroscopy. Even though electron energy loss spectroscopy (EELS) in transmission has recently been shown to probe local vibrational charge responses1-4, such studies are still limited by momentum space integration due to the focused beam geometry; they are also restricted to polar materials such as boron nitride or oxides1-4, in which huge signals induced by strong dipole moments are present. On the other hand, measurements on graphene performed by inelastic X-ray (neutron) scattering spectroscopy5-7 or EELS in reflection8,9 do not have any spatial resolution and require large microcrystals. Here we provide a new pathway to determine phonon dispersions down to the scale of an individual free-standing graphene monolayer by mapping the distinct vibrational modes for a large momentum transfer. The measured scattering intensities are accurately reproduced and interpreted with density functional perturbation theory10. Additionally, a nanometre-scale mapping of selected momentum-resolved vibrational modes using graphene nanoribbon structures has enabled us to spatially disentangle bulk, edge and surface vibrations. Our results are a proof-of-principle demonstration of the feasibility of studying local vibrational modes in two-dimensional monolayer materials at the nanometre scale.
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32
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Krivanek O, Dellby N, Hachtel J, Idrobo JC, Hotz M, Plotkin-Swing B, Bacon N, Bleloch A, Corbin G, Hoffman M, Meyer C, Lovejoy T. Progress in ultrahigh energy resolution EELS. Ultramicroscopy 2019; 203:60-67. [DOI: 10.1016/j.ultramic.2018.12.006] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 12/08/2018] [Accepted: 12/09/2018] [Indexed: 11/28/2022]
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33
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Hachtel JA, Huang J, Popovs I, Jansone-Popova S, Keum JK, Jakowski J, Lovejoy TC, Dellby N, Krivanek OL, Idrobo JC. Identification of site-specific isotopic labels by vibrational spectroscopy in the electron microscope. Science 2019; 363:525-528. [DOI: 10.1126/science.aav5845] [Citation(s) in RCA: 93] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 12/28/2018] [Indexed: 01/25/2023]
Abstract
The identification of isotopic labels by conventional macroscopic techniques lacks spatial resolution and requires relatively large quantities of material for measurements. We recorded the vibrational spectra of an α amino acid, l-alanine, with damage-free “aloof” electron energy-loss spectroscopy in a scanning transmission electron microscope to directly resolve carbon-site–specific isotopic labels in real space with nanoscale spatial resolution. An isotopic red shift of 4.8 ± 0.4 milli–electron volts in C–O asymmetric stretching modes was observed for 13C-labeled l-alanine at the carboxylate carbon site, which was confirmed by macroscopic infrared spectroscopy and theoretical calculations. The accurate measurement of this shift opens the door to nondestructive, site-specific, spatially resolved identification of isotopically labeled molecules with the electron microscope.
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34
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Hage FS, Kepaptsoglou DM, Ramasse QM, Allen LJ. Phonon Spectroscopy at Atomic Resolution. PHYSICAL REVIEW LETTERS 2019; 122:016103. [PMID: 31012678 DOI: 10.1103/physrevlett.122.016103] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Indexed: 05/28/2023]
Abstract
Advances in source monochromation in transmission electron microscopy have opened up new possibilities for investigations of condensed matter using the phonon-loss sector of the energy-loss spectrum. Here, we explore the spatial variations of the spectrum as an atomic-sized probe is scanned across a thin flake of hexagonal boron nitride. We demonstrate that phonon spectral mapping of atomic structure is possible. These results are consistent with a model for the quantum excitation of phonons and confirm that Z-contrast imaging is based on inelastic scattering associated with phonon excitation.
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Affiliation(s)
- F S Hage
- SuperSTEM Laboratory, SciTech Daresbury Campus, Daresbury WA4 4AD, United Kingdom
| | - D M Kepaptsoglou
- SuperSTEM Laboratory, SciTech Daresbury Campus, Daresbury WA4 4AD, United Kingdom
- York JEOL Nanocentre and Department of Physics, University of York, Heslington, York YO10 5BR, United Kingdom
| | - Q M Ramasse
- SuperSTEM Laboratory, SciTech Daresbury Campus, Daresbury WA4 4AD, United Kingdom
- School of Physics and School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - L J Allen
- School of Physics, University of Melbourne, Parkville, Victoria 3010, Australia
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, 52425 Jülich, Germany
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35
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Jokisaari JR, Hachtel JA, Hu X, Mukherjee A, Wang C, Konecna A, Lovejoy TC, Dellby N, Aizpurua J, Krivanek OL, Idrobo JC, Klie RF. Vibrational Spectroscopy of Water with High Spatial Resolution. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1802702. [PMID: 30062804 DOI: 10.1002/adma.201802702] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 06/02/2018] [Indexed: 05/15/2023]
Abstract
The ability to examine the vibrational spectra of liquids with nanometer spatial resolution will greatly expand the potential to study liquids and liquid interfaces. In fact, the fundamental properties of water, including complexities in its phase diagram, electrochemistry, and bonding due to nanoscale confinement are current research topics. For any liquid, direct investigation of ordered liquid structures, interfacial double layers, and adsorbed species at liquid-solid interfaces are of interest. Here, a novel way of characterizing the vibrational properties of liquid water with high spatial resolution using transmission electron microscopy is reported. By encapsulating water between two sheets of boron nitride, the ability to capture vibrational spectra to quantify the structure of the liquid, its interaction with the liquid-cell surfaces, and the ability to identify isotopes including H2 O and D2 O using electron energy-loss spectroscopy is demonstrated. The electron microscope used here, equipped with a high-energy-resolution monochromator, is able to record vibrational spectra of liquids and molecules and is sensitive to surface and bulk morphological properties both at the nano- and micrometer scales. These results represent an important milestone for liquid and isotope-labeled materials characterization with high spatial resolution, combining nanoscale imaging with vibrational spectroscopy.
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Affiliation(s)
- Jacob R Jokisaari
- Department of Physics, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Jordan A Hachtel
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Xuan Hu
- Department of Physics, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Arijita Mukherjee
- Department of Physics, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Canhui Wang
- Department of Physics, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Andrea Konecna
- Center for Material Physics (CSIC-UPV/EHU) and DIPC, Donostia - San Sebastián Gipuzkoa, 20018, Spain
| | | | - Niklas Dellby
- Nion Company, 11511 NE 118th St., Kirkland, WA, 98034, USA
| | - Javier Aizpurua
- Center for Material Physics (CSIC-UPV/EHU) and DIPC, Donostia - San Sebastián Gipuzkoa, 20018, Spain
| | | | - Juan-Carlos Idrobo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Robert F Klie
- Department of Physics, University of Illinois at Chicago, Chicago, IL, 60607, USA
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36
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Hage FS, Nicholls RJ, Yates JR, McCulloch DG, Lovejoy TC, Dellby N, Krivanek OL, Refson K, Ramasse QM. Nanoscale momentum-resolved vibrational spectroscopy. SCIENCE ADVANCES 2018; 4:eaar7495. [PMID: 29951584 PMCID: PMC6018998 DOI: 10.1126/sciadv.aar7495] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 05/01/2018] [Indexed: 05/21/2023]
Abstract
Vibrational modes affect fundamental physical properties such as the conduction of sound and heat and can be sensitive to nano- and atomic-scale structure. Probing the momentum transfer dependence of vibrational modes provides a wealth of information about a materials system; however, experimental work has been limited to essentially bulk and averaged surface approaches or to small wave vectors. We demonstrate a combined experimental and theoretical methodology for nanoscale mapping of optical and acoustic phonons across the first Brillouin zone, in the electron microscope, probing a volume ~1010 to 1020 times smaller than that of comparable bulk and surface techniques. In combination with more conventional electron microscopy techniques, the presented methodology should allow for direct correlation of nanoscale vibrational mode dispersions with atomic-scale structure and chemistry.
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Affiliation(s)
- Fredrik S. Hage
- SuperSTEM Laboratory, SciTech Daresbury Campus, Keckwick Lane, Daresbury WA4 4AD, UK
- Corresponding author. (Q.M.R.); (F.S.H.)
| | - Rebecca J. Nicholls
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK
| | - Jonathan R. Yates
- Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK
| | - Dougal G. McCulloch
- Physics, School of Science, RMIT University, Melbourne, Victoria 3001, Australia
| | | | - Niklas Dellby
- Nion Company, 11511 NE 118th Street, Kirkland, WA 98034, USA
| | - Ondrej L. Krivanek
- Nion Company, 11511 NE 118th Street, Kirkland, WA 98034, USA
- Department of Physics, Arizona State University, Tempe, AZ 85287, USA
| | - Keith Refson
- STFC (Science & Technology Facilities Council) Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, UK
- Department of Physics, Royal Holloway, University of London, Egham TW20 0EX, UK
| | - Quentin M. Ramasse
- SuperSTEM Laboratory, SciTech Daresbury Campus, Keckwick Lane, Daresbury WA4 4AD, UK
- School of Physics, University of Leeds, Leeds LS2 9JT, UK
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, UK
- Corresponding author. (Q.M.R.); (F.S.H.)
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37
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Exploring the capabilities of monochromated electron energy loss spectroscopy in the infrared regime. Sci Rep 2018; 8:5637. [PMID: 29618757 PMCID: PMC5884780 DOI: 10.1038/s41598-018-23805-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Accepted: 03/19/2018] [Indexed: 11/09/2022] Open
Abstract
Monochromated electron energy loss spectroscopy (EELS) is one of the leading techniques to study materials properties that correspond to low (<5 eV) energy losses (i.e. band-gaps, plasmons, and excitons) with nanoscale spatial resolution. Recently a new generation of monochromators have become available, opening regimes and unlocking excitations that were previously unobservable in the electron microscope. The capabilities of these new instruments are still being explored, and here we study the effect of monochromation on various aspects of EELS analysis in the infrared (<1 eV) regime. We investigate the effect of varying levels of monochromation on energy resolution, zero-loss peak (ZLP) tail reduction, ZLP tail shape, signal-to-noise-ratio, and spatial resolution. From these experiments, the new capabilities of monochromated EELS are shown to be highly promising for the future of localized spectroscopic analysis.
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38
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Idrobo JC, Lupini AR, Feng T, Unocic RR, Walden FS, Gardiner DS, Lovejoy TC, Dellby N, Pantelides ST, Krivanek OL. Temperature Measurement by a Nanoscale Electron Probe Using Energy Gain and Loss Spectroscopy. PHYSICAL REVIEW LETTERS 2018; 120:095901. [PMID: 29547334 DOI: 10.1103/physrevlett.120.095901] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 01/12/2018] [Indexed: 05/26/2023]
Abstract
Heat dissipation in integrated nanoscale devices is a major issue that requires the development of nanoscale temperature probes. Here, we report the implementation of a method that combines electron energy gain and loss spectroscopy to provide a direct measurement of the local temperature in the nanoenvironment. Loss and gain peaks corresponding to an optical-phonon mode in boron nitride were measured from room temperature to ∼1600 K. Both loss and gain peaks exhibit a shift towards lower energies as the sample is heated up. First-principles calculations of the temperature-induced phonon frequency shifts provide insights into the origin of this effect and confirm the experimental data. The experiments and theory presented here open the doors to the study of anharmonic effects in materials by directly probing phonons in the electron microscope.
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Affiliation(s)
- Juan Carlos Idrobo
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Andrew R Lupini
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Tianli Feng
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - Raymond R Unocic
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Franklin S Walden
- Protochips Company, 3800 Gateway Centre Boulevard, Suite 306, Morrisville, North Carolina 27560, USA
| | - Daniel S Gardiner
- Protochips Company, 3800 Gateway Centre Boulevard, Suite 306, Morrisville, North Carolina 27560, USA
| | - Tracy C Lovejoy
- Nion Company, 11511 NE 118th Street, Kirkland, Washington 98034, USA
| | - Niklas Dellby
- Nion Company, 11511 NE 118th Street, Kirkland, Washington 98034, USA
| | - Sokrates T Pantelides
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
- Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235, USA
| | - Ondrej L Krivanek
- Nion Company, 11511 NE 118th Street, Kirkland, Washington 98034, USA
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39
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Venkatraman K, Rez P, March K, Crozier PA. The influence of surfaces and interfaces on high spatial resolution vibrational EELS from SiO2. Microscopy (Oxf) 2018; 67:i14-i23. [DOI: 10.1093/jmicro/dfy003] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 01/09/2018] [Indexed: 11/14/2022] Open
Affiliation(s)
- Kartik Venkatraman
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona, USA
| | - Peter Rez
- Department of Physics, Arizona State University, Tempe, Arizona, USA
| | - Katia March
- LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona, USA
| | - Peter A Crozier
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona, USA
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40
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Lagos MJ, Trügler A, Amarasinghe V, Feldman LC, Hohenester U, Batson PE. Excitation of long-wavelength surface optical vibrational modes in films, cubes and film/cube composite system using an atom-sized electron beam. Microscopy (Oxf) 2018; 67:i3-i13. [DOI: 10.1093/jmicro/dfx130] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 12/16/2017] [Indexed: 11/13/2022] Open
Affiliation(s)
- Maureen J Lagos
- Department of Physics and Astronomy
- Department of Materials and Science Engineering, Rutgers University, Piscataway, NJ 08854, USA
- Institute for Advanced Materials, Devices, and Nanotechnology, Rutgers University, Piscataway, NJ 08854, USA
| | - Andreas Trügler
- Institute of Physics, University of Graz, Universitätsplatz 5, Graz 8010, Austria
| | - Voshadhi Amarasinghe
- Institute for Advanced Materials, Devices, and Nanotechnology, Rutgers University, Piscataway, NJ 08854, USA
| | - Leonard C Feldman
- Department of Physics and Astronomy
- Department of Materials and Science Engineering, Rutgers University, Piscataway, NJ 08854, USA
- Institute for Advanced Materials, Devices, and Nanotechnology, Rutgers University, Piscataway, NJ 08854, USA
| | - Ulrich Hohenester
- Institute of Physics, University of Graz, Universitätsplatz 5, Graz 8010, Austria
| | - Philip E Batson
- Department of Physics and Astronomy
- Department of Materials and Science Engineering, Rutgers University, Piscataway, NJ 08854, USA
- Institute for Advanced Materials, Devices, and Nanotechnology, Rutgers University, Piscataway, NJ 08854, USA
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41
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Crozier PA. Vibrational and valence aloof beam EELS: A potential tool for nondestructive characterization of nanoparticle surfaces. Ultramicroscopy 2017; 180:104-114. [DOI: 10.1016/j.ultramic.2017.03.011] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 03/10/2017] [Accepted: 03/11/2017] [Indexed: 11/25/2022]
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42
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Egerton R. Scattering delocalization and radiation damage in STEM-EELS. Ultramicroscopy 2017; 180:115-124. [DOI: 10.1016/j.ultramic.2017.02.007] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 02/04/2017] [Accepted: 02/18/2017] [Indexed: 11/29/2022]
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43
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Radtke G, Taverna D, Lazzeri M, Balan E. First-Principles Vibrational Electron Energy Loss Spectroscopy of β-Guanine. PHYSICAL REVIEW LETTERS 2017; 119:027402. [PMID: 28753326 DOI: 10.1103/physrevlett.119.027402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Indexed: 06/07/2023]
Abstract
A general approach to model vibrational electron energy loss spectra obtained using an electron beam positioned away from the specimen is presented. The energy-loss probability of the fast electron is evaluated using first-principles quantum mechanical calculations (density functional theory) of the dielectric response of the specimen. The validity of the method is assessed using recently measured anhydrous β-guanine, an important molecular solid used by animals to produce structural colors. The good agreement between theory and experiments lays the basis for a quantitative interpretation of this spectroscopy in complex systems.
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Affiliation(s)
- G Radtke
- Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC) Sorbonne Universités-UPMC Univ Paris 06, UMR CNRS 7590, Muséum National d'Histoire Naturelle, IRD UMR 206, 4 Place Jussieu, F-75005 Paris, France
| | - D Taverna
- Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC) Sorbonne Universités-UPMC Univ Paris 06, UMR CNRS 7590, Muséum National d'Histoire Naturelle, IRD UMR 206, 4 Place Jussieu, F-75005 Paris, France
| | - M Lazzeri
- Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC) Sorbonne Universités-UPMC Univ Paris 06, UMR CNRS 7590, Muséum National d'Histoire Naturelle, IRD UMR 206, 4 Place Jussieu, F-75005 Paris, France
| | - E Balan
- Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC) Sorbonne Universités-UPMC Univ Paris 06, UMR CNRS 7590, Muséum National d'Histoire Naturelle, IRD UMR 206, 4 Place Jussieu, F-75005 Paris, France
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Howie A. New instrumentation and cutting edge research. Ultramicroscopy 2017; 180:52-58. [PMID: 28258870 DOI: 10.1016/j.ultramic.2016.11.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Revised: 11/04/2016] [Accepted: 11/15/2016] [Indexed: 11/16/2022]
Abstract
Stimulated by Ondrej Krivanek's contributions, the complex interaction between research and innovations in the instrumentation for electron microscopy is discussed. Specific attention is given to aberration correction and to spectroscopy in both the valence region and at the energies of localised phonons or bond vibrations. Current thinking about projection imaging and dielectric excitation theory may be challenged. More significantly in the new fields of investigation opened up to them, electron microscopists will need to build closer relations, particularly with the photonics and scanning tunnelling microscopy communities. Further improvements in instrumentation could usefully be directed towards imaging and spectroscopy at higher scattering angles as well as the incorporation of other facilities such as photon stimulation and secondary electron imaging.
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Affiliation(s)
- A Howie
- Dept. of Physics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
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Lovejoy T, Rez P, Dellby N. Ondrej Krivanek: A pioneering visionary in electron microscopy. Ultramicroscopy 2017; 180:2-7. [PMID: 28347543 DOI: 10.1016/j.ultramic.2017.02.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Revised: 01/29/2017] [Accepted: 02/18/2017] [Indexed: 11/16/2022]
Abstract
This article is a short biographical sketch of the life and times of Ondrej Krivanek. The story starts with his early days in Prague, Czechia, and briefly outlines various events from a PhD in Cambridge to post-docs in Kyoto, Bell Labs, and building his first spectrometer at UC Berkeley. Ondrej's pioneering contributions to electron microscopy as Assistant Professor at Arizona State University and later as Director of R&D at Gatan are covered, as well as his return to academia and focusing on aberration correction. The story wraps up with the founding of Nion, the early success of the Nion aberration correctors, and subsequent progress such as building a complete cutting-edge electron microscope and later a record-breaking monochromator. Ondrej continues to be actively involved in design and in running Nion, and while this article ends at the present, further breakthroughs can be expected from him.
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Affiliation(s)
- Tracy Lovejoy
- Nion Co., 11511 NE 118th St., Kirkland, WA 98034, USA.
| | - Peter Rez
- Department of Physics, Arizona State University, Tempe, Arizona 85287, USA
| | - Niklas Dellby
- Nion Co., 11511 NE 118th St., Kirkland, WA 98034, USA
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