Re-examining Electron-Fermi Relaxation in Gold Films With a Nonlinear Thermoreflectance Model

Hopkins, Patrick E.; Phinney, Leslie M.; Serrano, Justin Raymond

doi:10.1115/1.4002778

Cited by 28 publications

(47 citation statements)

References 25 publications

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“…We fit the data before the peak by accounting for a delay in thermalization of the electron system. 26 In agreement with the previous data on electron thermalization time in Au, 26,34-38 we find thermalization time of the excited electrons in our experiments is between 800 fs to 1.1 ps. This implies that the electron system is nearly fully thermalized during electron-phonon relaxation, as discussed by Guo et al 14 We find that for all fluences and samples, only minor adjustments to A ee and B ep (by less than 10%) are necessary to achieve a best fit.…”

supporting

confidence: 93%

“…17,26 Thermal coupling between the electron and phonon systems in the Au films is governed by G eff ; G eff is distinct from the intrinsic rate of electron-phonon coupling in a metal, G, since G should not be affected by electron-electron or electroninterface scattering. 15 However, the measured response in a film is a convolution of all of these relaxation mechanisms.…”

mentioning

confidence: 99%

“…We use the procedure that we have outlined previously to determine the rate of electron relaxation. 26 Since our probe beam energy is well below the interband transition threshold of Au (Ref. 1) and our maximum electron temperatures do not excite d-band electrons, 15 we use a Drude-based thermoreflectivity model in our analysis.…”

mentioning

confidence: 99%

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Ultrafast and steady-state laser heating effects on electron relaxation and phonon coupling mechanisms in thin gold films

Hopkins

Duda

Kaehr

et al. 2013

Applied Physics Letters

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confidence: 93%

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confidence: 99%

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Ultrafast and steady-state laser heating effects on electron relaxation and phonon coupling mechanisms in thin gold films

Hopkins

Duda

Kaehr

et al. 2013

Applied Physics Letters

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“…The data is normalized by the maximum magnitude of the signal from the lock-in amplifier. The predicted maximum effective electron temperature in this data is 1,750±120 K with a G eff =2.90±0.2×16 W m −3 K −1 , which is in good agreement with previous literature [97,104]. The dotted lines in Fig.…”

Section: The Two-temperature Modelsupporting

confidence: 92%

“…is the source term that is modified to account for the delayed relaxation in the electronic distribution [97]. Note, in the limit of T e = T p , Eq.…”

Section: The Two-temperature Modelmentioning

confidence: 99%

The Role of Electronic and Vibrational Scattering on Thermal Transport Across Multiple Interfaces in Nanostructures

Giri¹

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Rapid miniaturization and faster working speeds in electronic devices has led to challenges in their thermal mitigation. However, thermal conductivity of the constituent materials in the nano-devices, even though a very critical parameter in their design, is mostly overlooked and the thermal performance of the device is mainly controlled through packaging techniques. However, it would be advantageous for a diverse spectrum of technologies, which ultimately fail due to either high density of interfaces or due to high operating frequencies, to control and tune thermal properties at the submicron length scale and femtoto-picosecond time scales. Therefore, a comprehensive understanding of how heat flows across nanosystems that are mostly limited by interfacial thermal transport would prove to be quintessential for the design of various electronic devices. For example, the contribution of electronic thermal resistance across metal/semiconductor interfaces has been a subject of debate for the past several decades; understanding the intrinsic electron-electron, electron-phonon and electron-boundary scattering mechanisms in these devices could potentially lead to transistors with higher operating frequencies. Moreover, with the advent of new fabrication technologies, the role of phononic-driven thermal resistances across hybrid interfaces of inorganic/organic materials and amorphous semiconductor superlattices (SLs) with high density of interfaces has largely been unexplored.It is the goal of this work to comprehensively explore interfacial thermal transport in these material systems by understanding the fundamental scattering mechanisms of the energy carriers, which dominate thermal transport at various length and time scales. In this regard, a combination of time-domain thermoreflectance (TDTR) experiments and non-equilibrium molecular dynamics (NEMD) simulations will be implemented to achieve these goals.The nonequilibrium between electrons and phonons at metal/semiconductor interfaces in high frequency microelectronic devices serves as a bottleneck to heat transfer in these ii devices. To understand this phenomena, TDTR is used to probe the highly non-equilibrium condition that is induced due to pulse absorption by thin Au films deposited on various dielectric substrates. For electron temperature excursions of ≤ 3,500 K in Au, it is shown that while the increase in the excited carrier density increases the e-p coupling in the metal, the bond strength between the metal and the substrate dictates the energy transfer rate across the interface during this highly non-equilibrium time regime. Furthermore, at time scales when the electrons have fully thermalized with the lattice, electron-phonon coupling does not influence the phonon-driven thermal boundary conductance.Another phenomena that lead to device failure are the phonon-driven thermal boundary resistance in multilayered semiconductors used in technologies such as thermoelectric power generation or phase change memory devices. TDTR is used to simultaneously...

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Unconventional Shrinkage of Hot Electron Distribution in Metal Directly Visualized by Ultrafast Imaging

et al. 2023

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Elucidation of hot carrier transport and cooling mechanisms at the micro‐/nanoscale is critical for optoelectronics, thermal management, and photocatalysis. Spatiotemporal evolution of hot electrons is usually convoluted with their ultrafast dynamics. Herein, an ultrafast microscopy is employed to directly track the spatiotemporal distribution of photoexcited hot electrons, providing a transformative approach to unravel the competitive relationship of transport and cooling. In the temporal evolution profiles of hot electron distribution, an anomalous contracting stage showing obvious thickness and fluence dependency is observed, with a characteristic end time indicating the completion of electron–phonon (e‐ph) thermalization. Hot electron transport plays a prominent role in the competition with e‐ph coupling, while interfacial heat dissipation dominates nonequilibrium state evolution with thickness below ballistic length. This work significantly enriches the tool kit of ultrafast techniques and provides guidance for rational design and optimization of micro‐/nanodevices.

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Re-examining Electron-Fermi Relaxation in Gold Films With a Nonlinear Thermoreflectance Model

Cited by 28 publications

References 25 publications

Ultrafast and steady-state laser heating effects on electron relaxation and phonon coupling mechanisms in thin gold films

Ultrafast and steady-state laser heating effects on electron relaxation and phonon coupling mechanisms in thin gold films

The Role of Electronic and Vibrational Scattering on Thermal Transport Across Multiple Interfaces in Nanostructures

Unconventional Shrinkage of Hot Electron Distribution in Metal Directly Visualized by Ultrafast Imaging

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