1
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Akerboom E, Di Giulio V, Schilder NJ, García de Abajo FJ, Polman A. Free Electron-Plasmon Coupling Strength and Near-Field Retrieval through Electron Energy-Dependent Cathodoluminescence Spectroscopy. ACS NANO 2024; 18:13560-13567. [PMID: 38742710 PMCID: PMC11140833 DOI: 10.1021/acsnano.3c12972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 04/11/2024] [Accepted: 04/25/2024] [Indexed: 05/16/2024]
Abstract
Tightly confined optical near fields in plasmonic nanostructures play a pivotal role in important applications ranging from optical sensing to light harvesting. Energetic electrons are ideally suited to probing optical near fields by collecting the resulting cathodoluminescence (CL) light emission. Intriguingly, the CL intensity is determined by the near-field profile along the electron propagation direction, but the retrieval of such field from measurements has remained elusive. Furthermore, the conditions for optimum electron near-field coupling in plasmonic systems are critically dependent on such field and remain experimentally unexplored. In this work, we use electron energy-dependent CL spectroscopy to study the tightly confined dipolar mode in plasmonic gold nanoparticles. By systematically studying gold nanoparticles with diameters in the range of 20-100 nm and electron energies from 4 to 30 keV, we determine how the coupling between swift electrons and the optical near fields depends on the energy of the incoming electron. The strongest coupling is achieved when the electron speed equals the mode phase velocity, meeting the so-called phase-matching condition. In aloof experiments, the measured data are well reproduced by electromagnetic simulations, which explain that larger particles and faster electrons favor a stronger electron near-field coupling. For penetrating electron trajectories, scattering at the particle produces severe corrections of the trajectory that defy existing theories based on the assumption of nonrecoil condition. Therefore, we develop a first-order recoil correction model that allows us to account for inelastic electron scattering, rendering better agreement with measured data. Finally, we consider the albedo of the particles and find that, to approach unity coupling, a highly confined electric field and very slow electrons are needed, both representing experimental challenges. Our findings explain how to reach unity-order coupling between free electrons and confined excitations, helping us understand fundamental aspects of light-matter interaction at the nanoscale.
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Affiliation(s)
- Evelijn Akerboom
- Center
for Nanophotonics, NWO-Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
| | - Valerio Di Giulio
- ICFO-Institut
de Ciencies Fotoniques, The Barcelona Institute
of Science and Technology, Castelldefels, 08860 Barcelona, Spain
| | - Nick J. Schilder
- Center
for Nanophotonics, NWO-Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
- Gleb
Wataghin Physics Institute, University of
Campinas, Campinas 13083-859, Brazil
| | - F. Javier García de Abajo
- ICFO-Institut
de Ciencies Fotoniques, The Barcelona Institute
of Science and Technology, Castelldefels, 08860 Barcelona, Spain
- ICREA-Institució
Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Spain
| | - Albert Polman
- Center
for Nanophotonics, NWO-Institute AMOLF, Science Park 104, 1098 XG Amsterdam, The Netherlands
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2
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Taylor EJ, Iyer V, Dhami BS, Klein C, Lawrie BJ, Appavoo K. Hyperspectral mapping of nanoscale photophysics and degradation processes in hybrid perovskite at the single grain level. NANOSCALE ADVANCES 2023; 5:4687-4695. [PMID: 37705772 PMCID: PMC10496886 DOI: 10.1039/d3na00529a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 08/14/2023] [Indexed: 09/15/2023]
Abstract
With solar cells reaching 26.1% certified efficiency, hybrid perovskites are now the most efficient thin film photovoltaic material. Though substantial effort has focussed on synthesis approaches and device architectures to further improve perovskite-based solar cells, more work is needed to correlate physical properties of the underlying film structure with device performance. Here, using cathodoluminescence microscopy coupled with unsupervised machine learning, we quantify how nanoscale heterogeneity globally builds up within a large morphological grain of hybrid perovskite when exposed to extrinsic stimuli such as charge accumulation from electron beams or milder environmental factors like humidity. The converged electron-beam excitation allows us to map PbI2 and the emergence of other intermediate phases with high spatial and energy resolution. In contrast with recent reports of hybrid perovskite cathodoluminescence, we observe no significant change in the PbI2 signatures, even after high-energy electron beam excitation. In fact, we can exploit the stable PbI2 signatures to quantitatively map how hybrid perovskites degrade. Moreover, we show how our methodology allows disentangling of the photophysics associated with photon recycling and band-edge emission with sub-micron resolution using a fundamental understanding of electron interactions in hybrid perovskites.
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Affiliation(s)
- Ethan J Taylor
- Department of Physics, University of Alabama at Birmingham 1300 University Blvd., Birmingham AL 35294 USA
| | - Vasudevan Iyer
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Bibek S Dhami
- Department of Physics, University of Alabama at Birmingham 1300 University Blvd., Birmingham AL 35294 USA
| | - Clay Klein
- Clarion University 840 Wood St, Clarion PA 16214 USA
| | - Benjamin J Lawrie
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory Oak Ridge TN 37831 USA
- Materials Science and Technology Division, Oak Ridge National Laboratory Oak Ridge TN 37831 USA
| | - Kannatassen Appavoo
- Department of Physics, University of Alabama at Birmingham 1300 University Blvd., Birmingham AL 35294 USA
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3
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McPolin CPT, Vila YN, Krasavin AV, Llorca J, Zayats AV. Multimode hybrid gold-silicon nanoantennas for tailored nanoscale optical confinement. NANOPHOTONICS 2023; 12:2997-3005. [PMID: 37457505 PMCID: PMC10344444 DOI: 10.1515/nanoph-2023-0105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 04/25/2023] [Indexed: 07/18/2023]
Abstract
High-index dielectric nanoantennas, which provide an interplay between electric and magnetic modes, have been widely used as building blocks for a variety of devices and metasurfaces, both in linear and nonlinear regimes. Here, we investigate hybrid metal-semiconductor nanoantennas, consisting of a multimode silicon nanopillar core coated with a gold layer, that offer an enhanced degree of control over the mode selection and confinement, and emission of light on the nanoscale exploiting high-order electric and magnetic resonances. Cathodoluminescence spectra revealed a multitude of resonant modes supported by the nanoantennas due to hybridization of the Mie resonances of the core and the plasmonic resonances of the shell. Eigenmode analysis revealed the modes that exhibit enhanced field localization at the gold interface, together with high confinement within the nanopillar volume. Consequently, this architecture provides a flexible means of engineering nanoscale components with tailored optical modes and field confinement for a plethora of applications, including sensing, hot-electron photodetection and nanophotonics with cylindrical vector beams.
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Affiliation(s)
- Cillian P. T. McPolin
- Department of Physics and London Centre for Nanotechnology, King’s College London, Strand, LondonWC2R 2LS, UK
| | - Yago N. Vila
- Department of Physics and London Centre for Nanotechnology, King’s College London, Strand, LondonWC2R 2LS, UK
- Universitat Politècnica de Catalunya, Escola Tècnica Superior d’Enginyeria de Telecomunicacions de Barcelona, Barcelona, Spain
| | - Alexey V. Krasavin
- Department of Physics and London Centre for Nanotechnology, King’s College London, Strand, LondonWC2R 2LS, UK
| | - Jordi Llorca
- Department of Chemical Engineering, Universitat Politècnica de Catalunya, EEBE, Barcelona, Spain
| | - Anatoly V. Zayats
- Department of Physics and London Centre for Nanotechnology, King’s College London, Strand, LondonWC2R 2LS, UK
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4
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García
de Abajo FJ, Di Giulio V. Optical Excitations with Electron Beams: Challenges and Opportunities. ACS PHOTONICS 2021; 8:945-974. [PMID: 35356759 PMCID: PMC8939335 DOI: 10.1021/acsphotonics.0c01950] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 02/17/2021] [Accepted: 02/19/2021] [Indexed: 05/20/2023]
Abstract
Free electron beams such as those employed in electron microscopes have evolved into powerful tools to investigate photonic nanostructures with an unrivaled combination of spatial and spectral precision through the analysis of electron energy losses and cathodoluminescence light emission. In combination with ultrafast optics, the emerging field of ultrafast electron microscopy utilizes synchronized femtosecond electron and light pulses that are aimed at the sampled structures, holding the promise to bring simultaneous sub-Å-sub-fs-sub-meV space-time-energy resolution to the study of material and optical-field dynamics. In addition, these advances enable the manipulation of the wave function of individual free electrons in unprecedented ways, opening sound prospects to probe and control quantum excitations at the nanoscale. Here, we provide an overview of photonics research based on free electrons, supplemented by original theoretical insights and discussion of several stimulating challenges and opportunities. In particular, we show that the excitation probability by a single electron is independent of its wave function, apart from a classical average over the transverse beam density profile, whereas the probability for two or more modulated electrons depends on their relative spatial arrangement, thus reflecting the quantum nature of their interactions. We derive first-principles analytical expressions that embody these results and have general validity for arbitrarily shaped electrons and any type of electron-sample interaction. We conclude with some perspectives on various exciting directions that include disruptive approaches to noninvasive spectroscopy and microscopy, the possibility of sampling the nonlinear optical response at the nanoscale, the manipulation of the density matrices associated with free electrons and optical sample modes, and appealing applications in optical modulation of electron beams, all of which could potentially revolutionize the use of free electrons in photonics.
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Affiliation(s)
- 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
- E-mail:
| | - Valerio Di Giulio
- ICFO-Institut
de Ciencies Fotoniques, The Barcelona Institute
of Science and Technology, 08860 Castelldefels, Barcelona, Spain
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5
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Liebtrau M, Sivis M, Feist A, Lourenço-Martins H, Pazos-Pérez N, Alvarez-Puebla RA, de Abajo FJG, Polman A, Ropers C. Spontaneous and stimulated electron-photon interactions in nanoscale plasmonic near fields. LIGHT, SCIENCE & APPLICATIONS 2021; 10:82. [PMID: 33859160 PMCID: PMC8050270 DOI: 10.1038/s41377-021-00511-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 03/01/2021] [Accepted: 03/12/2021] [Indexed: 05/29/2023]
Abstract
The interplay between free electrons, light, and matter offers unique prospects for space, time, and energy resolved optical material characterization, structured light generation, and quantum information processing. Here, we study the nanoscale features of spontaneous and stimulated electron-photon interactions mediated by localized surface plasmon resonances at the tips of a gold nanostar using electron energy-loss spectroscopy (EELS), cathodoluminescence spectroscopy (CL), and photon-induced near-field electron microscopy (PINEM). Supported by numerical electromagnetic boundary-element method (BEM) calculations, we show that the different coupling mechanisms probed by EELS, CL, and PINEM feature the same spatial dependence on the electric field distribution of the tip modes. However, the electron-photon interaction strength is found to vary with the incident electron velocity, as determined by the spatial Fourier transform of the electric near-field component parallel to the electron trajectory. For the tightly confined plasmonic tip resonances, our calculations suggest an optimum coupling velocity at electron energies as low as a few keV. Our results are discussed in the context of more complex geometries supporting multiple modes with spatial and spectral overlap. We provide fundamental insights into spontaneous and stimulated electron-light-matter interactions with key implications for research on (quantum) coherent optical phenomena at the nanoscale.
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Affiliation(s)
- Matthias Liebtrau
- Center for Nanophotonics, AMOLF, 1098 XG, Amsterdam, The Netherlands.
| | - Murat Sivis
- 4th Physical Institute-Solids and Nanostructures, University of Göttingen, 37077, Göttingen, Germany
- Max Plank Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | - Armin Feist
- 4th Physical Institute-Solids and Nanostructures, University of Göttingen, 37077, Göttingen, Germany
- Max Plank Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | - Hugo Lourenço-Martins
- 4th Physical Institute-Solids and Nanostructures, University of Göttingen, 37077, Göttingen, Germany
- Max Plank Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | - Nicolas Pazos-Pérez
- Department of Physical Chemistry and EMaS, Universitat Rovira i Virgili, 43007, Tarragona, Spain
| | - Ramon A Alvarez-Puebla
- Department of Physical Chemistry and EMaS, Universitat Rovira i Virgili, 43007, Tarragona, Spain
- ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010, Barcelona, Spain
| | - F Javier García de Abajo
- ICREA-Institució Catalana de Recerca i Estudis Avançats, 08010, Barcelona, Spain
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860, Castelldefels (Barcelona), Spain
| | - Albert Polman
- Center for Nanophotonics, AMOLF, 1098 XG, Amsterdam, The Netherlands
| | - Claus Ropers
- 4th Physical Institute-Solids and Nanostructures, University of Göttingen, 37077, Göttingen, Germany
- Max Plank Institute for Biophysical Chemistry, 37077, Göttingen, Germany
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6
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Wong LJ, Rivera N, Murdia C, Christensen T, Joannopoulos JD, Soljačić M, Kaminer I. Control of quantum electrodynamical processes by shaping electron wavepackets. Nat Commun 2021; 12:1700. [PMID: 33731697 PMCID: PMC7969958 DOI: 10.1038/s41467-021-21367-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 01/14/2021] [Indexed: 01/31/2023] Open
Abstract
Fundamental quantum electrodynamical (QED) processes, such as spontaneous emission and electron-photon scattering, encompass phenomena that underlie much of modern science and technology. Conventionally, calculations in QED and other field theories treat incoming particles as single-momentum states, omitting the possibility that coherent superposition states, i.e., shaped wavepackets, can alter fundamental scattering processes. Here, we show that free electron waveshaping can be used to design interferences between two or more pathways in a QED process, enabling precise control over the rate of that process. As an example, we show that free electron waveshaping modifies both spatial and spectral characteristics of bremsstrahlung emission, leading for instance to enhancements in directionality and monochromaticity. The ability to tailor general QED processes opens up additional avenues of control in phenomena ranging from optical excitation (e.g., plasmon and phonon emission) in electron microscopy to free electron lasing in the quantum regime.
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Affiliation(s)
- Liang Jie Wong
- School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, Singapore.
| | - Nicholas Rivera
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Chitraang Murdia
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Thomas Christensen
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - John D Joannopoulos
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Marin Soljačić
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Ido Kaminer
- Department of Electrical Engineering, Technion, Haifa, Israel.
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7
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Liu ACY, Lloyd J, Coenen T, Gómez DE. Mapping Local Surface Plasmon Modes in a Nanoplasmonic Trimer Using Cathodoluminescence in the Scanning Electron Microscope. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2020; 26:808-813. [PMID: 32366354 DOI: 10.1017/s1431927620000094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The excitability of local surface plasmon modes in radial trimers composed of gold nanorods was mapped using hyperspectral cathodoluminescence (CL) in the scanning electron microscope. In symmetric trimers, the local plasmon resonances could be excited most effectively at the ends of individual rods. Introducing asymmetry into the structure breaks the degeneracy of the dipole modes and changes the excitability of transverse dipole modes in different directions. CL in the scanning electron microscope has great potential to interrogate individual nanophotonic structures and is a complement to electron energy loss spectroscopy and optical microscopy.
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Affiliation(s)
- Amelia C Y Liu
- School of Physics and Astronomy, Monash University, Clayton, VIC3800, Australia
- Monash Centre for Electron Microscopy, Monash University, Clayton, VIC3800, Australia
| | - Julian Lloyd
- Department of Chemical Engineering, Monash University, Clayton, VIC3800, Australia
| | - Toon Coenen
- DELMIC BV, Kanaalweg 4, 2628 EB, Delft, The Netherlands
| | - Daniel E Gómez
- School of Applied Science, RMIT University, Melbourne, VIC3000, Australia
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8
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Cox JD, García de Abajo FJ. Nonlinear Interactions between Free Electrons and Nanographenes. NANO LETTERS 2020; 20:4792-4800. [PMID: 32401522 DOI: 10.1021/acs.nanolett.0c00538] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Free electrons act as a source of highly confined, spectrally broad optical fields that are widely used to map photonic modes with nanometer/millielectronvolt space/energy resolution through currently available electron energy-loss and cathodoluminescence spectroscopies. These techniques are understood as probes of the linear optical response, while nonlinear dynamics has escaped observation with similar degree of spatial detail, despite the strong enhancement of the electron evanescent field with decreasing electron energy. Here, we show that the field accompanying low-energy electrons can trigger anharmonic response in strongly nonlinear materials. Specifically, through realistic quantum-mechanical simulations, we find that the interaction between ≲100 eV electrons and plasmons in graphene nanostructures gives rise to substantial optical nonlinearities that are discernible as saturation and spectral shifts in the plasmonic features revealed in the cathodoluminescence emission and electron energy-loss spectra. Our results support the use of low-energy electron-beam spectroscopies for the exploration of nonlinear optical processes in nanostructures.
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Affiliation(s)
- Joel D Cox
- Center for Nano Optics, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
- Danish Institute for Advanced Study, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - 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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9
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Schilder NJ, Agrawal H, Garnett EC, Polman A. Phase-Resolved Surface Plasmon Scattering Probed by Cathodoluminescence Holography. ACS PHOTONICS 2020; 7:1476-1482. [PMID: 32566698 PMCID: PMC7304075 DOI: 10.1021/acsphotonics.0c00209] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Indexed: 05/20/2023]
Abstract
High-energy (1-100 keV) electrons can coherently couple to plasmonic and dielectric nanostructures, creating cathodoluminescence (CL) of which the spectral features reveal details of the material's resonant modes at a deep-subwavelength spatial resolution. While CL provides fundamental insight in optical modes, detecting its phase has remained elusive. Here, we use Fourier-transform CL holography to determine the far-field phase distribution of fields scattered from plasmonic nanoholes, nanocubes, and helical nanoapertures and reconstruct the angle-resolved phase distributions. From the derived fields, we derive the relative strength and phase of induced scattering dipoles. Fourier-transform CL holography opens up a new world of coherent light scattering and surface wave studies with nanoscale spatial resolution.
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Affiliation(s)
- Nick J. Schilder
- Center for Nanophotonics, AMOLFScience Park 104, 1098XG Amsterdam, The Netherlands
| | - Harshal Agrawal
- Center for Nanophotonics, AMOLFScience Park 104, 1098XG Amsterdam, The Netherlands
| | - Erik C. Garnett
- Center for Nanophotonics, AMOLFScience Park 104, 1098XG Amsterdam, The Netherlands
| | - Albert Polman
- Center for Nanophotonics, AMOLFScience Park 104, 1098XG Amsterdam, The Netherlands
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10
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Wallum A, Nguyen HA, Gruebele M. Excited-State Imaging of Single Particles on the Subnanometer Scale. Annu Rev Phys Chem 2020; 71:415-433. [DOI: 10.1146/annurev-physchem-071119-040108] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
At the intersection of spectroscopy and microscopy lie techniques that are capable of providing subnanometer imaging of excited states of individual molecules or nanoparticles. Such approaches are particularly important for imaging macromolecules or nanoparticles large enough to have a high probability of containing a defect. These inevitable defects often control properties and function despite an otherwise ideal structure. We discuss real-space imaging techniques such as using scanning tunneling microscopy tips to enhance optical measurements and electron energy-loss spectroscopy in a scanning transmission electron microscope, which is based on focused electron beams to obtain high-resolution spatial information on excited states. The outlook for these methods is bright, as they will provide critical information for the characterization and improvement of energy-switching, electron-switching, and energy-harvesting materials.
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Affiliation(s)
- Alison Wallum
- Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Huy A. Nguyen
- Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Martin Gruebele
- Department of Chemistry and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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11
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Polman A, Kociak M, García de Abajo FJ. Electron-beam spectroscopy for nanophotonics. NATURE MATERIALS 2019; 18:1158-1171. [PMID: 31308514 DOI: 10.1038/s41563-019-0409-1] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Revised: 05/04/2019] [Accepted: 05/14/2019] [Indexed: 05/22/2023]
Abstract
Progress in electron-beam spectroscopies has recently enabled the study of optical excitations with combined space, energy and time resolution in the nanometre, millielectronvolt and femtosecond domain, thus providing unique access into nanophotonic structures and their detailed optical responses. These techniques rely on ~1-300 keV electron beams focused at the sample down to sub-nanometre spots, temporally compressed in wavepackets a few femtoseconds long, and in some cases controlled by ultrafast light pulses. The electrons undergo energy losses and gains (also giving rise to cathodoluminescence light emission), which are recorded to reveal the optical landscape along the beam path. This Review portraits these advances, with a focus on coherent excitations, emphasizing the increasing level of control over the electron wavefunctions and ensuing applications in the study and technological use of optically resonant modes and polaritons in nanoparticles, 2D materials and engineered nanostructures.
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Affiliation(s)
- Albert Polman
- Center for Nanophotonics, AMOLF, Amsterdam, the Netherlands.
| | - Mathieu Kociak
- Laboratoire de Physique des Solides, Université de Paris-Sud, Orsay, France
| | - F Javier García de Abajo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels (Barcelona), Spain
- ICREA-Institució Catalana de Reserca I Estudis Avançats, Barcelona, Spain
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