Observation of Hot-Electron Pressure in the Vibration Dynamics of Metal Nanoparticles

Perner, M.; Grésillon, S.; März, Josefine; Plessen, G. von; Feldmann, Jochen; Porstendörfer, J.; Berg, K.‐J.; Berg, Gunnar

doi:10.1103/physrevlett.85.792

Cited by 211 publications

(245 citation statements)

References 15 publications

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“…3 to a forced simple harmonic oscillator model with damping, following previously proposed models for coherent excitation of acoustic modes in nanocrystals 18,40 . Here the nanocrystal displacement follows the equation:…”

Section: Discussionmentioning

confidence: 99%

Visualization of nanocrystal breathing modes at extreme strains

et al. 2015

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Nanoscale dimensions in materials lead to unique electronic and structural properties with applications ranging from site-specific drug delivery to anodes for lithium-ion batteries. These functional properties often involve large-amplitude strains and structural modifications, and thus require an understanding of the dynamics of these processes. Here we use femtosecond X-ray scattering techniques to visualize, in real time and with atomic-scale resolution, light-induced anisotropic strains in nanocrystal spheres and rods. Strains at the percent level are observed in CdS and CdSe samples, associated with a rapid expansion followed by contraction along the nanosphere or nanorod radial direction driven by a transient carrierinduced stress. These morphological changes occur simultaneously with the first steps in the melting transition on hundreds of femtosecond timescales. This work represents the first direct real-time probe of the dynamics of these large-amplitude strains and shape changes in few-nanometre-scale particles.

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Section: Discussionmentioning

confidence: 99%

Visualization of nanocrystal breathing modes at extreme strains

et al. 2015

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“…In detail, it is known that for metal nanoparticles there are two different mechanisms present, one from the direct pressure of the hot electron gas and one from the new equilibrium size due to thermal expansion. 23,32,33 On the other hand, the phase may also depend on the boundary conditions, in particular the particles internal structure.…”

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confidence: 99%

A Surface Phase Transition of Supported Gold Nanoparticles

et al. 2007

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A thermal phase transition has been resolved in gold nanoparticles supported on a surface. By use of asynchronous optical sampling with coupled femtosecond oscillators, the Lamb vibrational modes could be resolved as a function of annealing temperature. At a temperature of 104°C the damping rate and phase changes abruptly, indicating a structural transition in the particle, which is explained as the onset of surface melting.Metallic nanoparticles are in the focus of fundamental and applied research. They show an optical response in the visible region that depends strongly on size, shape, and local dielectric environment, 1 making them appealing for nanoscale sensor applications. The interaction with light shows interesting peculiarities, such as ultrafast relaxation dynamics, coupling to nonradiative processes, or near field enhancement. 2 In particular nanoscale gold particles have received strong attention due to their versatile synthesis protocols, 3 shape transformations, or binding to biological molecules. 4 They served also to understand the generic structural properties that scale with size or shape. The melting point depression with decreasing particle size represents one of the prominent features, arising from the change in ratio between surface and bulk atoms and the reduction in binding energy. Since the seminal publication of Buffat and Borel 5 several improvements of the description have been made, while the general relation of the melting point depression ∆T mp ∝ 1/D as a function of size D remains valid. One of these points is the existence of surface melting, i.e., a coexistence of a liquid-like layer of atoms at the surface with the solid core material at temperatures below the respective melting point. 6,7 While this effect seems to be very basic, there is still a lack of unambiguous experimental proof regarding the details, in particular for gold nanoparticles.Inasawa et al. 8 have tried to investigate the shape transformation of elongated particles on a surface induced by static heating (ex situ) and concluded that a transformation into spheres takes places at temperatures as low as 400°C. A similar, very recent study has shown that nanorods with a large aspect ratio of the axes can be transformed at 200°C into spheres and partial relaxation occurs much earlier (100°C). 9 Surface melting is taken as the origin for these relaxations.It should also be borne in mind that the relaxation of rods could also be caused by other forces, as has been shown by laser-induced melting, 10 where the onset correlates with dislocations in the interior, as the rods are subjected to a large uniaxial strain due to surface tension.Hartland et al. have also reported on several experiments, which aimed at the structural transformations on a very short time scale, initiated by femtosecond excitation. 11,12 The vibrational response of the particles has been recorded by optical pump-probe techniques, reflecting the mechanical properties of the particles. While the change of the elastic constants of the spheres ...

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“…Plasmons are effective for localizing light in a subwavelength volume and are ideal candidates for manipulating nanoscale mechanical motion because of their large absorption cross-sections, subwavelength field localization and high sensitivity to geometry and refractive index changes. This efficient absorption makes the plasmon an effective transducer of far-field radiation into phonons 5 : the plasmonic nanostructure absorbs energy from the laser pulse and rapidly expands, generating coherent acoustic phonons through impulsive thermal excitation [11][12][13][14] . When a metallic nanostructure first absorbs an ultrashort laser pulse, a localized surface plasmon, a coherent oscillation of electrons, is excited.…”

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confidence: 99%

Ultrafast acousto-plasmonic control and sensing in complex nanostructures

et al. 2014

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Coherent acoustic phonons modulate optical, electronic and mechanical properties at ultrahigh frequencies and can be exploited for applications such as ultratrace chemical detection, ultrafast lasers and transducers. Owing to their large absorption cross-sections and high sensitivities, nanoplasmonic resonators are used to generate coherent phonons up to terahertz frequencies. Generating, detecting and controlling such ultrahigh frequency phonons has been a topic of intense research. Here we report that by designing plasmonic nanostructures exhibiting multimodal phonon interference, we can detect the spatial properties of complex phonon modes below the optical wavelength through the interplay between plasmons and phonons. This allows detection of complex nanomechanical dynamics by polarization-resolved transient absorption spectroscopy. Moreover, we demonstrate that the multiple vibrational states in nanostructures can be tailored by manipulating the geometry and dynamically selected by acousto-plasmonic coherent control. This allows enhancement, detection and coherent generation of tunable strains using surface plasmons.

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Observation of Hot-Electron Pressure in the Vibration Dynamics of Metal Nanoparticles

Cited by 211 publications

References 15 publications

Visualization of nanocrystal breathing modes at extreme strains

Visualization of nanocrystal breathing modes at extreme strains

A Surface Phase Transition of Supported Gold Nanoparticles

Ultrafast acousto-plasmonic control and sensing in complex nanostructures

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