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Open Access Publications from the University of California

Differentiating Photoexcited Carrier and Phonon Dynamics in the Δ, L, and Γ Valleys of Si(100) with Transient Extreme Ultraviolet Spectroscopy

  • Author(s): Cushing, Scott K
  • Lee, Angela
  • Porter, Ilana J
  • Carneiro, Lucas M
  • Chang, Hung-Tzu
  • Zürch, Michael
  • Leone, Stephen R
  • et al.

© 2019 American Chemical Society. Transient extreme ultraviolet (XUV) spectroscopy probes core level transitions to unoccupied valence and conduction band states. Uncertainty remains as to what degree the core-hole created by the XUV transition modifies the measurement of photoexcited electron and hole energies. Here, the Si L 2,3 edge is measured after photoexcitation of electrons to the δ, L, and σ valleys of Si(100). The measured changes in the XUV transition probability do not energetically agree with the increasing electron photoexcitation energy. The data experimentally confirm that, for the Si L 2,3 edge, the time-dependent electron and hole energies are partially obscured by the core-hole perturbation. A model based on many-body approximations and the Bethe-Salpeter equation is successfully used to predict the core-hole modification of the final transition density of states in terms of both electronic and structural dynamics. The resulting fit time constants match the excited-state electron thermalization time and the intervalley electron-phonon, intravalley electron-phonon, and phonon-phonon scattering times previously measured in silicon. The outlined approach is a more comprehensive framework for interpreting transient XUV absorption spectra in photoexcited semiconductors.

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