Surface plasmon assisted control of hot-electron relaxation time

Memarzadeh, Sarvenaz; Kim, Jong Bum; Aytac, Yigit; Murphy, Thomas E.; Munday, Jeremy N.

doi:10.1364/optica.385959

Cited by 12 publications

(9 citation statements)

References 51 publications

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“…Transient absorption spectroscopy can effectively explore photogenerated electronic kinetic parameters through monitoring real-time changing process of nanocrystal absorption after illumination, − which may be an effective means for segmented metal/metal HJNRs to examine the SPR modes, hot electron lifetimes, and thermal dissipation rates of its internal photogenerated electrons. The electron–phonon (e-ph) scattering process is an extremely important part of electronic dynamics of metal NPs, , the e-ph scattering time of which associates with excitation power and surface characteristic, surrounding medium, size, and shape of metal NPs. − Moreover, the synergistic effects between different components, contact interfaces, and heterojunction contents of segmented metal/metal HJNRs are perhaps expected to have unique e-ph scattering behavior, which is rarely studied to date.…”

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confidence: 99%

Segmented Ag–Au–Ag Heterojunction Nanorods: Pressure-Assisted Aqueous-Phase Synthesis and Engineered Femtosecond-to-Nanosecond Dynamics

Chen

Wang

et al. 2021

J. Phys. Chem. Lett.

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Segmented metal−metal heterostructure nanorods/nanowires are very promising for development in photoelectric devices, wearable electronics, biomedicine, and energy storage due to unique surface and interface and adjustable electronic and optical properties. Regretfully, most of the segmented heterojunctions are presently synthesized in organic solvent, and its electronic dynamics is still rarely studied and poorly understood. Here, we reported a pressure-assisted one-step aqueous-phase strategy to successfully synthesize segmented Ag−Au−Ag heterojunction nanorods (HJNRs), the aspect ratios and heterojunction contents of which can be well controlled by varying pressure value. The heterojunction-induced femtosecond-to-nanosecond dynamics in 1D direction of the Ag−Au− Ag HJNRs were for the first time acquired and presented a unique regularity tendency (e.g., electron−phonon scattering time). The unprecedented aqueous-phase strategy opens up horizons of synthesis of other segmented metal−metal HJNRs, and the fascinating Ag−Au−Ag HJNRs are hopeful for the development of a new class devices in photothermal and photoelectronic fields.

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confidence: 99%

Segmented Ag–Au–Ag Heterojunction Nanorods: Pressure-Assisted Aqueous-Phase Synthesis and Engineered Femtosecond-to-Nanosecond Dynamics

Chen

Wang

et al. 2021

J. Phys. Chem. Lett.

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“…Laser fluence and electric field confinement caused by the surface plasmon resonance are external factors that can modify the hot‐electrons relaxation dynamics. [ 90 ] It has also been shown that sample geometry and the material's band structure affect the relaxation time of the hot electrons. [ 91 ] These results suggest that the complex interplay between the atoms and the electrons in alloyed metals presents an additional route for tuning of hot carrier dynamics.…”

Section: Applicationsmentioning

confidence: 99%

Emergent Opportunities with Metallic Alloys: From Material Design to Optical Devices

Gong

Lyu

Palm

et al. 2020

Advanced Optical Materials

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devices is the fact that their dielectric function (i.e., permittivity, ε = ε 1 + iε 2) is predefined. Thus, several research groups, including ours, have recently merged two almost orthogonal fields, photo nics, and metallurgy, to pursue metallic materials with arbitrary permit tivity. [1-5] Alloying is now a burgeoning framework for achieving materials with engineered optical properties, encom passing both nanostructures and thin films, as will be surveyed in this Review. Plasmonics exploits the interaction of incident electromagnetic fields with the col lective motion of free electrons (plasmons) in metals. This phenomenon confines the electromagnetic fields in close vicinity of the metal interfaces, dramatically enhancing the electrical field intensity surrounding the material. [6-8] Plasmons can be divided into two categories: surface plasmon polaritons (SPP) that propagate along the metal and dielectric interface, and localized surface plasmon resonance (LSPR) that are confined in a subwavelength nanostructure. For the latter, their optical scattering or absorp tion (and/or the nearby dielectrics and semiconductors) can be significantly increased. As a result, these enhancement effects are the underpinnings to a range of novel optical processes, and have found countless applications in photovoltaics, [9-11] photo catalysis, [12-14] bio and chemicalsensing, [15,16] electrooptical modu lation, [17,18] and superabsorbers. [19-21] As expected, the features of either type of plasmon are strongly dependent upon the dielectric function of the material, which is somewhat fixed in metals. Concerning materials, coinage metals, such as Au, Ag, or Cu, are widely used in photonics due to their abundant free electrons and chemical stability. [1] Other noble metals including Metallic nanostructures and thin films are fundamental building blocks for next-generation nanophotonics. Yet, the fixed permittivity of pure metals often imposes limitations on the materials employed and/or on device performance. Alternatively, metallic mixtures, or alloys, represent a promising pathway to tailor the optical and electrical properties of devices, enabling further control of the electromagnetic spectrum. In this Review, a survey of recent advances in photonics and plasmonics achieved using metal alloys is presented. An overview of the primary fabrication methods to obtain subwavelength alloyed nanostructures is provided, followed by an in-depth analysis of experimental and theoretical studies of their optical properties, including their correlation with band structure. The broad landscape of optical devices that can benefit from metallic materials with engineered permittivity is also discussed, spanning from superabsorbers and hydrogen sensors to photovoltaics and hot electron devices. This Review concludes with an outlook of potential research directions that would benefit from the on demand optical properties of metallic mixtures, leading to new optoelectronic materials and device opportunities.

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“…To find the excited hot-carriers relaxation time from the transient reflectivity measurements, we employ the combination of a free-electron model [44] and the modified two-temperature model [37].…”

Section: Theory and Analysismentioning

confidence: 99%

“…We further employ the Kretschmann geometry to couple into the propagating surface plasmon mode, which has the added benefit of increasing the measurement sensitivity as a result of increased photon absorption. To determine the hot-carrier lifetime, we use a free-electron model and convert the differential reflectivity measurements to the corresponding elevated electron temperature [37]. Our results show that the hot-carrier relaxation time depends upon the Ag mole fractions.…”

Section: Introductionmentioning

confidence: 98%

Control of hot-carrier relaxation time in Au-Ag thin films through alloying

Memarzadeh¹,

Palm²,

Murphy³

et al. 2020

Opt. Express

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The plasmon resonance of a structure is primarily dictated by its optical properties and geometry, which can be modified to enable hot-carrier photodetectors with superior performance. Recently, metal-alloys have played a prominent role in tuning the resonance of plasmonic structures through chemical composition engineering. However, it has been unclear how alloying modifies the time dynamics of generated hot-carriers. In this work, we elucidate the role of chemical composition on the relaxation time of hot-carriers for the archetypal Aux Ag1-x thin film system. Through timeresolved optical spectroscopy measurements in the visible wavelength range, we measure composition-dependent relaxation times that vary up to 8x for constant pump fluency. Surprisingly, we find that the addition of 2% of Ag into Au films can increase the hot carrier lifetime by approximately 35% under fixed fluence, as a result of a decrease in optical loss. Further, the relaxation time is found to be inversely proportional to the imaginary part of the permittivity.Our results indicate that alloying is a promising approach to effectively control hot-carrier relaxation time in metals.

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Surface plasmon assisted control of hot-electron relaxation time

Cited by 12 publications

References 51 publications

Segmented Ag–Au–Ag Heterojunction Nanorods: Pressure-Assisted Aqueous-Phase Synthesis and Engineered Femtosecond-to-Nanosecond Dynamics

Segmented Ag–Au–Ag Heterojunction Nanorods: Pressure-Assisted Aqueous-Phase Synthesis and Engineered Femtosecond-to-Nanosecond Dynamics

Emergent Opportunities with Metallic Alloys: From Material Design to Optical Devices

Control of hot-carrier relaxation time in Au-Ag thin films through alloying

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