Femtosecond thermoreflectivity and thermotransmissivity of polycrystalline and single-crystalline gold films

Elsayed-Ali, Hani E.; Juhász, Tibor; Smith, G. O.; Bron, W. E.

doi:10.1103/physrevb.43.4488

Cited by 192 publications

(152 citation statements)

References 19 publications

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“…[29][30][31][32] It should be noted that the G-factors estimated by Kaganov's model became nearly constant in the range of the electron temperature, indicating that this model fails to describe the temperature dependency of the electron-phonon coupling. Hence, Kaganov's model is excluded from further discussion.…”

Section: Wmmentioning

confidence: 99%

Comparison of Theoretical Models of Electron-Phonon Coupling in Thin Gold Films Irradiated by Femtosecond Pulse Lasers

2011

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This study reports on a comparison of theoretical models for electron-phonon coupling that is substantially associated with nonequilibrium energy transport in thin gold films irradiated by femtosecond pulse lasers. Three published electron-phonon coupling models were analyzed with the use of a well-established two-temperature model to describe non-equilibrium energy transport between electrons and phonons. Based on the numerical results, at lower fluence, all models showed nearly similar tendencies, whereas at higher fluence, constant electronphonon coupling forced unrealistically long electron-phonon equilibration times and spatially long diffusive regions as it failed to intrinsically consider the effect of a high number density of excited d-band electrons. Even at higher fluence, however, both Lin's and Chen's models yielded physically reasonable results, showing converging electron-phonon equilibration times and steep gradients in the spatial lattice temperature profiles at higher laser fluence. In particular, Lin's model predicts nonlinear characteristics of heat capacity and lattice temperature with respect to laser fluence better than Chen's model. Moreover, the electron-phonon relaxation time increased with laser fluence, whereas at laser fluence greater than 0.05 J/cm 2 , the thermal equilibrium time was nearly independent of the laser fluence. Thus, it was concluded that Lin's model better predicted the electron-phonon coupling phenomena in thin metal films irradiated by ultra-short pulse lasers.

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Section: Wmmentioning

confidence: 99%

Comparison of Theoretical Models of Electron-Phonon Coupling in Thin Gold Films Irradiated by Femtosecond Pulse Lasers

2011

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“…All the parameters of the second simulation are identical to the ones used in the first simulation, except for the range of the ballistic energy transport that is reduced from 56 nm in the first simulation (see Section II) to 18 nm. We assume that the presence of the voids and enhancement of the electron scattering by the high density of grain boundaries and crystal defects [64,65] propagating toward the surface acts in accord with the unloading wave propagating from the surface of the target and contributes to the rapid expansion of the surface region. The expansion leads to the fast cooling (Fig.…”

Section: Spallation By 2 Nd Pulse: Connection To Incubation Effectmentioning

confidence: 99%

Generation of subsurface voids and a nanocrystalline surface layer in femtosecond laser irradiation of a single-crystal Ag target

et al. 2015

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Structural transformations in a shallow surface region of a bulk Ag (001) target irradiated by a femtosecond laser pulse are investigated in large-scale atomistic simulations and experiments.The simulations reveal a complex interplay of fast laser melting, rapid resolidification, and the dynamic relaxation of laser-induced stresses that leads to the formation of a sub-surface porous region covered by a nanocrystalline surface layer. The generation of the porous region is consistent with the experimental observation of surface "swelling" occurring at laser fluences below the spallation/ablation threshold and may be related to the incubation effect in multi-pulse laser ablation of metals. The nanocrystalline layer is produced by massive nucleation of crystallites triggered by a deep undercooling of the melted surface region experiencing fast quenching at a rate on the order of 10 11 K/s. The predicted surface structure features random crystallographic orientation of nanograins and a high density of stacking faults, twins, and nanoscale twinned structural elements with five-fold symmetry, which suggests high hardness and possible enhancement of catalytic activity of the surface.

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“…The microscopic mechanisms in plasmon decays across various energy, length, and time scales are still a subject of considerable debate, as seen in recent experimental [11,12] and theoretical literature [13][14][15][16]. The decay of surface plasmons generates hot carriers through several mechanisms, including direct interband transitions, phonon-assisted intraband transitions, and geometry-assisted intraband transitions, as we have shown in previous work [17,18].Dynamics of hot carriers are typically studied via ultrafast pump-probe measurements of plasmonic nanostructures using a high-intensity laser pulse to excite a large number of electrons and measure the optical response as a function of time using a delayed probe pulse [11,[19][20][21][22][23][24][25]. Various studies have taken advantage of this technique to investigate electron-electron scattering, electron-phonon coupling, and electronic transport [20,22,[26][27][28][29][30][31][32].…”

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confidence: 99%

Experimental and Ab Initio Ultrafast Carrier Dynamics in Plasmonic Nanoparticles

et al. 2017

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Ultrafast pump-probe measurements of plasmonic nanostructures probe the nonequilibrium behavior of excited carriers, which involves several competing effects obscured in typical empirical analyses. Here we present pump-probe measurements of plasmonic nanoparticles along with a complete theoretical description based on first-principles calculations of carrier dynamics and optical response, free of any fitting parameters. We account for detailed electronic-structure effects in the density of states, excited carrier distributions, electron-phonon coupling, and dielectric functions that allow us to avoid effective electron temperature approximations. Using this calculation method, we obtain excellent quantitative agreement with spectral and temporal features in transient-absorption measurements. In both our experiments and calculations, we identify the two major contributions of the initial response with distinct signatures: short-lived highly nonthermal excited carriers and longer-lived thermalizing carriers. DOI: 10.1103/PhysRevLett.118.087401 Plasmonic hot carriers provide tremendous opportunities for combining efficient light capture with energy conversion [1][2][3][4][5] and catalysis [6,7] at the nanoscale [8][9][10]. The microscopic mechanisms in plasmon decays across various energy, length, and time scales are still a subject of considerable debate, as seen in recent experimental [11,12] and theoretical literature [13][14][15][16]. The decay of surface plasmons generates hot carriers through several mechanisms, including direct interband transitions, phonon-assisted intraband transitions, and geometry-assisted intraband transitions, as we have shown in previous work [17,18].Dynamics of hot carriers are typically studied via ultrafast pump-probe measurements of plasmonic nanostructures using a high-intensity laser pulse to excite a large number of electrons and measure the optical response as a function of time using a delayed probe pulse [11,[19][20][21][22][23][24][25]. Various studies have taken advantage of this technique to investigate electron-electron scattering, electron-phonon coupling, and electronic transport [20,22,[26][27][28][29][30][31][32]. Figure 1 shows a representative map of the differential extinction cross section as a function of pump-probe delay time and probe wavelength. With an increase in electron temperature, the real part of the dielectric function near the resonant frequency becomes more negative, while the imaginary part increases [33]. This causes the resonance to broaden and blueshift at short times as the electron temperature rises rapidly, and then to narrow and shift back over longer times as electrons cool down, consistent with previous observations [34]. Taking a slice of the map at one probe wavelength reveals the temporal behavior of the electron relaxation [ Fig. 1(b)], whereas a slice of the map at one time gives the spectral response, as shown in Fig. 1(a) for a set of times relative to the delay time with maximum signal, t max ¼ 700 fs.Conventional analyses of pu...

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Femtosecond thermoreflectivity and thermotransmissivity of polycrystalline and single-crystalline gold films

Cited by 192 publications

References 19 publications

Comparison of Theoretical Models of Electron-Phonon Coupling in Thin Gold Films Irradiated by Femtosecond Pulse Lasers

Comparison of Theoretical Models of Electron-Phonon Coupling in Thin Gold Films Irradiated by Femtosecond Pulse Lasers

Generation of subsurface voids and a nanocrystalline surface layer in femtosecond laser irradiation of a single-crystal Ag target

Experimental and Ab Initio Ultrafast Carrier Dynamics in Plasmonic Nanoparticles

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