Evidence of Spatially Inhomogeneous Electron Temperature in a Resonantly Excited Array of Bow-Tie Nanoantennas

Lehr, Martin; Bley, Karina; Vogel, Nicolas; Rethfeld, B.; Schönhense, G.; Elmers, H. J.

doi:10.1021/acs.jpcc.9b03722

Cited by 11 publications

(9 citation statements)

References 81 publications

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“…8,69 Conversely, we note as a parting comment that photoemission angular distributions may be utilized to elucidate nanoplasmonic field distributions for different optical parameters and particle geometries, providing complementary information to photoemission spatial distributions from photoemission electron microscopy (PEEM) studies. 9,68,69 While PEEM spatial maps with tens-of-nanometer resolution provide a clear indication of hot spots and emissive regions correlated with nanoscale structure, single-nanoparticle angleresolved photoemission studies 5,8,49,70 can provide further details on the (3D) field distributions, so long as the photoexcitation/emission dynamics can be accurately modeled. Thus, with insights from the present studies, these and other nPPE techniques may be utilized to complement electron energy loss spectroscopy, 71 super-resolution imaging, 72 and scanning near-field optical techniques 7374,75 for mapping nanophotonic fields.…”

Section: Resultsmentioning

confidence: 99%

Controlling the Spatial and Momentum Distributions of Plasmonic Carriers: Volume vs Surface Effects

et al. 2021

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Hot carrier spatial and momentum distributions in nanoplasmonic systems depend sensitively on the optical excitation parameters and nanoscale geometry, which therefore determine the efficiency and functionality of plasmon-enhanced catalysts, photovoltaics, and nanocathodes. A growing appreciation over the past decade for the distinction between volumeand surface-mediated photoexcitation and electron emission from such systems has underscored the need for direct mechanistic insight and quantification of these two processes. Toward this end, we use angle-resolved photoelectron velocity mapping to directly distinguish volume and surface contributions to nanoplasmonic hot electron emission from gold nanorods as a function of aspect ratio, down to the spherical limit. Nanorods excited along their longitudinal surface plasmon axis exhibit surprising transverse photoemission distributions due to the dominant volume excitation mechanisms, as reproduced via ballistic Monte Carlo modelling. We further demonstrate a screening-induced transition from volume (transverse) to surface (longitudinal) photoemission with red detuning of the excitation laser and determine the relative cross-sections of the two mechanisms via combined volume and surface multiphoton photoemission modelling.Based on these results, we are able to identify geometry-and material-specific contributions to the photoemission cross-sections and offer general principles for designing nanoplasmonic systems to control hot electron excitation and emission distributions.

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Section: Resultsmentioning

confidence: 99%

Controlling the Spatial and Momentum Distributions of Plasmonic Carriers: Volume vs Surface Effects

et al. 2021

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“…The confinement could be used to enhance processes such as for single molecule Raman spectroscopy ,, and photochemistry . A unique characterization of bowtie antennas has been demonstrated by PEEM imaging with electron energy and momentum analysis . Lehr et al have shown that the total photoemission signal from the region around the bowtie antenna tips is a result of two distinct emission mechanisms: (i) the mPP process from a transient hot electron gas, characterized by its symmetric emission in the in-plane momentum space, and (ii) a field emission process resulting from the optical near-field enhancement at the antenna tips, with strongly anisotropic emission pattern that depends on the excitation phase.…”

Section: Plasmonic Antennas and Circuitsmentioning

confidence: 99%

“…402 A unique characterization of bowtie antennas has been demonstrated by PEEM imaging with electron energy and momentum analysis. 403 Lehr et al 403 have shown that the total photoemission signal from the region around the bowtie antenna tips is a result of two distinct emission mechanisms: (i) the mPP process from a transient hot electron gas, characterized by its symmetric emission in the in-plane momentum space, and (ii) a field emission process resulting from the optical near-field enhancement at the antenna tips, with strongly anisotropic emission pattern that depends on the excitation phase. Moreover, the results in ref 403 suggest a spatially inhomogeneous distribution of the hot electron gas temperature with the thermal energy extremum localized around the gap area of the bowtie antennas.…”

Section: Plasmonic Antennasmentioning

confidence: 99%

Ultrafast Photoemission Electron Microscopy: Imaging Plasmons in Space and Time

2020

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Plasmonics is a rapidly growing field spanning research and applications across chemistry, physics, optics, energy harvesting, and medicine. Ultrafast photoemission electron microscopy (PEEM) has demonstrated unprecedented power in the characterization of surface plasmons and other electronic excitations, as it uniquely combines the requisite spatial and temporal resolution, making it ideally suited for 3D space and time coherent imaging of the dynamical plasmonic phenomena on the nanofemto scale. The ability to visualize plasmonic fields evolving at the local speed of light on subwavelength scale with optical phase resolution illuminates old phenomena and opens new directions for growth of plasmonics research. In this review, we guide the reader thorough experimental description of PEEM as a characterization tool for both surface plasmon polaritons and localized plasmons and summarize the exciting progress it has opened by the ultrafast imaging of plasmonic phenomena on the nanofemto scale.

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“…Examining recent photoemission experiments with dominant surface-plasmon fields, ,,− it remains difficult to disentangle the fundamental plasmon decay from the multitude of physical effects that contribute to the observed nonlinear signals, including the influence of the driving laser. A temporal separation of the material response induced by the exciting laser pulse or the plasmon could in principle be achieved for experimental conditions for which the pulse duration is much shorter than the lifetime of an LSP at a nanostructure. , But, even in those cases, experimental access to the fundamental difference between plasmonic and photonic electron excitation is denied by the inability to obtain respective photoemission signals with exactly comparable conditions, e .…”

Section: Introductionmentioning

confidence: 99%

Energy and Momentum Distribution of Surface Plasmon-Induced Hot Carriers Isolated via Spatiotemporal Separation

et al. 2021

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Understanding the differences between photoninduced and plasmon-induced hot electrons is essential for the construction of devices for plasmonic energy conversion. The mechanism of the plasmonic enhancement in photochemistry, photocatalysis, and light-harvesting and especially the role of hot carriers is still heavily discussed. The question remains, if plasmon-induced and photon-induced hot carriers are fundamentally different or if plasmonic enhancement is only an effect of field concentration producing these carriers in greater numbers. For the bulk plasmon resonance, a fundamental difference is known, yet for the technologically important surface plasmons, this is far from being settled. The direct imaging of surface plasmon-induced hot carriers could provide essential insight, but the separation of the influence of driving laser, field-enhancement, and fundamental plasmon decay has proven to be difficult. Here, we present an approach using a two-color femtosecond pump−probe scheme in time-resolved 2-photonphotoemission (tr-2PPE), supported by a theoretical analysis of the light and plasmon energy flow. We separate the energy and momentum distribution of the plasmon-induced hot electrons from that of photoexcited electrons by following the spatial evolution of photoemitted electrons with energy-resolved photoemission electron microscopy (PEEM) and momentum microscopy during the propagation of a surface plasmon polariton (SPP) pulse along a gold surface. With this scheme, we realize a direct experimental access to plasmon-induced hot electrons. We find a plasmonic enhancement toward high excitation energies and small in-plane momenta, which suggests a fundamentally different mechanism of hot electron generation, as previously unknown for surface plasmons.

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Evidence of Spatially Inhomogeneous Electron Temperature in a Resonantly Excited Array of Bow-Tie Nanoantennas

Cited by 11 publications

References 81 publications

Controlling the Spatial and Momentum Distributions of Plasmonic Carriers: Volume vs Surface Effects

Controlling the Spatial and Momentum Distributions of Plasmonic Carriers: Volume vs Surface Effects

Ultrafast Photoemission Electron Microscopy: Imaging Plasmons in Space and Time

Energy and Momentum Distribution of Surface Plasmon-Induced Hot Carriers Isolated via Spatiotemporal Separation

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