Electron diffusion in metals studied by picosecond ultrasonics

Tas, Guray; Maris, Humphrey J.

doi:10.1103/physrevb.49.15046

Cited by 326 publications

(268 citation statements)

References 26 publications

Supporting

Mentioning

255

Contrasting

Order By: Relevance

“…The source term simulates excitation of the conduction band electrons by a laser pulse with a Gaussian temporal profile and reproduces the exponential attenuation of laser intensity with depth under the surface (Beer-Lambert law). In order to account for the energy transport occurring before the thermalization of the excited electrons [8,45,46], the optical absorption depth, L p = 12 nm at laser wavelength of 800 nm [47], is combined with the effective depth of the "ballistic" energy transport, L b = 56 nm, roughly estimated here as a product of the Fermi velocity and the Drude relaxation time [48]. This estimate is in a good agreement with a prediction of 53±7 nm derived from experiment [49].…”

Section: Parameters Of the Ttm Equation For The Electron Temperaturementioning

confidence: 99%

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

et al. 2015

View full text Add to dashboard Cite

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.

show abstract

Section: Parameters Of the Ttm Equation For The Electron Temperaturementioning

confidence: 99%

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

et al. 2015

View full text Add to dashboard Cite

show abstract

“…In metals, the relatively high density of final states gives rise to a momentum relaxation rate of the order of 10-20 femtoseconds 1 , primarily by electron-phonon scattering, whereas the very low density of states in semimetals suppresses relaxation of the momentum distribution towards thermodynamic equilibrium, particularly in transferring carriers between the electron and hole pockets 2,3 . Relaxation of the carrier energy distribution in metals (for carriers that differ in energy by less than 1 eV from the Fermi level) is substantially slower than momentum relaxation because it typically takes many electron-phonon scattering events to substantially change the energy of a carrier and strong screening of the Coulomb interaction by the dense electron plasma gives a carrier-carrier scattering time much larger than the carrier-phonon scattering time [4][5][6][7] . Thus, typical energy relaxation times in metals are of the order of 100 fs or more and both carriercarrier scattering and carrier-phonon scattering play a substantial role [5][6][7] .…”

Section: Introductionmentioning

confidence: 99%

“…We argue that as the plasma cools towards room temperature the electron-hole recombination rate and the plasma cooling rate should be of similar in magnitude as a greater proportion of the excited carriers lie in the energy range where the conduction and valence bands overlap. (In this picture, we implicitly assume that carrier distributions within each valley are close to thermal -this equilibrium being established by a combination of rapid carrier-carrier scattering and electron-phonon scattering -and that the relaxation time for the energy distribution of carriers within each valley is shorter than the intervalley scattering time 7 . )…”

Section: Introductionmentioning

confidence: 99%

Free-carrier relaxation and lattice heating in photoexcited bismuth

et al. 2013

View full text Add to dashboard Cite

We report ultrafast surface pump and interface probe experiments on photoexcited carrier transport across single crystal bismuth films on sapphire. The film thickness is sufficient to separate carrier dynamics from lattice heating and strain, allowing us to investigate the time-scales of momentum relaxation, heat transfer to the lattice and electron-hole recombination. The measured electron-hole (e − h) recombination time is 12-26 ps and ambipolar diffusivity is 18-40 cm 2 /s for carrier excitation up to ∼ 10 19 cm −3 . By comparing the heating of the front and back sides of the film, we put lower limits on the rate of heat transfer to the lattice, and by observing the decay of the plasma at the back of the film, we estimate the timescale of electron-hole recombination. We interpret each of these timescales within a common framework of electron-phonon scattering and find qualitative agreement between the various relaxation times observed. We find that the carrier density is not determined by the e − h plasma temperature after a few picoseconds. The diffusion and recombination become nonlinear with initial excitation > ∼ 10 20 cm −3 .

show abstract

“…These last years several research groups have developed and carried out more or less refined methods allowing to solve Boltzmann equation in order to describe the athermal regime in noble metals [73][74][75][76][77][78][79]. We have elaborated an approach partly similar to the one previously reported in Refs.…”

Section: Athermal Regime: Resolution Of the Boltzmann Equation 737475mentioning

confidence: 99%

“…We have elaborated an approach partly similar to the one previously reported in Refs. [77][78][79]. It is based on a dual-time relaxation approximation for eph scattering and the Landau theory of Fermi liquids for the e-e one.…”

Section: Athermal Regime: Resolution Of the Boltzmann Equation 737475mentioning

confidence: 99%

Gold nanoparticle assemblies: interplay between thermal effects and optical response

et al. 2008

View full text Add to dashboard Cite

The optical response of materials based on gold nanoparticle assemblies depends on many parameters regarding both material morphology and light excitation characteristics. In this paper, the interplay between the optical and thermal responses of such media is particularly investigated under its theoretical aspect. Both conventional and original modeling approaches are presented and applied to concrete cases. We first show how the interaction of light with matrix-embedded gold nanoparticles can result in the generation of thermal excitations through different energy exchange mechanisms. We then describe how thermal processes can affect the optical response of a nanoparticle assembly. Finally, we connect both aspects and point out their involvement in the nonlinear optical response of nanocomposite media. This allows us to tackle two key issues in the field of third-order nonlinear properties of gold nanoparticles: The influence of the generalized thermal lens in the long laser pulse regime and the hot electron contribution to the gold particle intrinsic third-order susceptibility, including its spectral dispersion and intensity-dependence. Additionally, we demonstrate the possible significant influence of the heat carrier ballistic regime and phonon rarefaction in the cooling dynamics of an embedded gold nanoparticle subsequent to ultrafast pulsed laser excitation.

show abstract

Electron diffusion in metals studied by picosecond ultrasonics

Cited by 326 publications

References 26 publications

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

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

Free-carrier relaxation and lattice heating in photoexcited bismuth

Gold nanoparticle assemblies: interplay between thermal effects and optical response

Contact Info

Product

Resources

About