Hot Electron Thermoreflectance Coefficient of Gold during Electron-Phonon Nonequilibrium

Elizabeth L. Radue, John A. Tomko, Ashutosh Giri, Jeffrey L. Braun, Xin Zhou, Oleg V. Prezhdo, Evan L. Runnerstrom, Jon Paul Maria, Patrick E. Hopkins

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

The temperature-dependent reflectivity of metals is quantified by the thermoreflectance coefficient, which is a material-dependent parameter that depends on the metallic band structure, electron scattering dynamics, and photon wavelength. After short-pulse laser heating, the electronic subsystem in a metal can be driven to temperatures much higher than that of the lattice, which gives rise to unique nonequilibrium electron and phonon scattering dynamics, leading to a "hot electron" thermoreflectance that is different from the traditionally measured equilibrium coefficient. In this work, we analytically quantify and experimentally measure this hot electron thermoreflectance coefficient through ultrafast pump-probe measurements of thin gold films on silica glass and sapphire substrates. We demonstrate the ability to not only quantify the thermoreflectance during electron-phonon nonequilibrium but also validate this coefficient's predicted dependence on the absolute temperature of the electronic subsystem. The approach outlined in this work provides a metrology to further understand and quantify excited-state scattering effects on the dielectric function of metals.

Original languageEnglish (US)
Pages (from-to)4880-4887
Number of pages8
JournalACS Photonics
Volume5
Issue number12
DOIs
StatePublished - Dec 19 2018

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biotechnology
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering

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    Radue, E. L., Tomko, J. A., Giri, A., Braun, J. L., Zhou, X., Prezhdo, O. V., Runnerstrom, E. L., Maria, J. P., & Hopkins, P. E. (2018). Hot Electron Thermoreflectance Coefficient of Gold during Electron-Phonon Nonequilibrium. ACS Photonics, 5(12), 4880-4887. https://doi.org/10.1021/acsphotonics.8b01045