An official website of the United States government
Plasmonic nanostructures have been demonstrated as emergent photocatalysts because of their efficient photon absorption and their ability to produce hot carriers. However, the plasmon-generated hot carriers decay through ultrafast relaxation pathways, resulting in a short lifetime that impedes the exploitation of hot carriers for chemical reactions. Charge separation at the heterojunction of the hybrid nanostructures can counteract the ultrafast decay to extend the carrier lifetime. Here, we fabricate hybrid nanostructures composed of gold nanorods and a carbon thin film and demonstrate efficient charge transfer between these two materials. Using single-particle dark-field scattering spectroscopy, we observe a broadening of the longitudinal plasmon for gold nanorods on a carbon film compared to those on a glass substrate. We attribute this plasmon damping to the electron transfer from gold nanorods to the carbon film and exclude the contribution from plasmon-induced resonance energy transfer. The electron transfer efficiencies are calculated as 52.8 ± 4.8 and 57.4 ± 4.0% for carbon films with thicknesses of 10 and 25 nm, respectively. This work demonstrates efficient charge separation at the gold–carbon film interface, which can extend the lifetime of hot carriers to promote plasmonic photocatalysts.
more »
« less
Determining hot-carrier transport dynamics from terahertz emission
Understanding the ultrafast excitation and transport dynamics of plasmon-driven hot carriers is critical to the development of optoelectronics, photochemistry, and solar-energy harvesting. However, the ultrashort time and length scales associated with the behavior of these highly out-of-equilibrium carriers have impaired experimental verification of ab initio quantum theories. Here, we present an approach to studying plasmonic hot-carrier dynamics that analyzes the temporal waveform of coherent terahertz bursts radiated by photo-ejected hot carriers from designer nano-antennas with a broken symmetry. For ballistic carriers ejected from gold antennas, we find an ~11-femtosecond timescale composed of the plasmon lifetime and ballistic transport time. Polarization- and phase-sensitive detection of terahertz fields further grant direct access to their ballistic transport trajectory. Our approach opens explorations of ultrafast carrier dynamics in optically excited nanostructures.
more »
« less
- Award ID(s):
- 2004749
- PAR ID:
- 10516610
- Publisher / Repository:
- American Association for the Advancement
- Date Published:
- Journal Name:
- Science
- Volume:
- 382
- Issue:
- 6668
- ISSN:
- 0036-8075
- Page Range / eLocation ID:
- 299 to 305
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)Hot-carriers in plasmonic nanostructures, generated via plasmon decay, play key roles in applications like photocatalysis and in photodetectors that circumvent band-gap limitations. However, direct experimental quantification of steady-state energy distributions of hot-carriers in nanostructures has so far been lacking. We present transport measurements from single-molecule junctions, created by trapping suitably chosen single molecules between an ultra-thin gold film supporting surface plasmon polaritons and a scanning probe tip, that can provide quantification of plasmonic hot-carrier distributions. Our results show that Landau damping is the dominant physical mechanism of hot-carrier generation in nanoscale systems with strong confinement. The technique developed in this work will enable quantification of plasmonic hot-carrier distributions in nanophotonic and plasmonic devices.more » « less
-
Physical processes involving hot electrons, including their generation, transport, injection, and relaxation, have been an extensive area of research. The most widely utilized method for actuating the creation of hot electrons involves the excitation of plasmonic modes followed by their non-radiative decay, channeling the energy into these energetic carriers. Since plasmonics has already evolved into a mature field of scientific exploration, active plasmonic devices serve as an ideal platform to study hot-electron physics. In this Perspective article, we will provide the reader with a comprehensive outline of the physics underlying hot-electron dynamics. Emphasis will be placed on the characteristic timescales involved with the lifecycle of hot electrons, the generation and decay mechanisms of surface plasmon-induced hot electrons, and the material platforms suitable for such a study. Then, we will move on to discuss different temperature models used to explain the evolution of hot electrons and the changes in the optical properties of the materials they are generated in or injected into. Finally, we will focus on some of the interesting optical phenomena occurring at ultrafast timescales mediated by hot-carrier dynamics. Such a discussion is expected to incorporate valuable insights into our understanding of the synergistic relationship between hot-electron dynamics and active plasmonics, thereby paving the way for novel applications involving optoelectronics and energy conversion.more » « less
-
Abstract Ultrafast optical switching in plasmonic platforms relies on the third‐order Kerr nonlinearity, which is tightly linked to the dynamics of hot carriers in nanostructured metals. Although extensively utilized, a fundamental understanding on the dependence of the switching dynamics upon optical resonances has often been overlooked. Here, all‐optical control of resonance bands in a hybrid photonic‐plasmonic crystal is employed as an empowering technique for probing the resonance‐dependent switching dynamics upon hot carrier formation. Differential optical transmission measurements reveal an enhanced switching performance near the anti‐crossing point arising from strong coupling between local and nonlocal resonance modes. Furthermore, entangled with hot‐carrier dynamics, the nonlinear correspondence between optical resonances and refractive index change results in tailorable dispersion of recovery speeds which can notably deviate from the characteristic lifetime of hot carriers. The comprehensive understanding provides new protocols for optically characterizing hot‐carrier dynamics and optimizing resonance‐based all‐optical switches for operations across the visible spectrum.more » « less
-
A terahertz (THz) metamaterial consisting of radiative slot antennas and subradiant complementary split-ring resonators exhibits plasmon induced opacity in a narrow spectral range due to the destructive interference between the bright and dark modes of the coupled oscillators. Femtosecond optical excitations instantly quench the mode coupling and plasmon oscillations, injecting photocarriers into the metamaterial. The plasmon resonances in the coupled metamaterial are restored by intense THz pulses in a subpicoseond time scale. The strong THz fields induce intervalley scattering and interband tunneling of the photocarriers and achieve significant reduction of the photocarrier mobility. The ultrafast dynamics of the nonlinear THz interactions reveals intricate interplay between photocarriers and plasmon oscillations. The high-field THz control of the plasmon oscillations implies potential applications to ultrahigh-speed plasmonics.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1126/science.adj5612
