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Transient birefringence and dichroism in ZnO studied with fs-time-resolved spectroscopic ellipsometry

Herrfurth, O. ; Richter, S. LU ; Rebarz, M. ; Espinoza, S. ; Zúñiga-Pérez, J. ; Deparis, C. ; Leveillee, J. ; Schleife, A. ; Grundmann, M. and Andreasson, J. LU , et al. (2021) In Physical Review Research 3(1).
Abstract

The full transient dielectric-function (DF) tensor of ZnO after UV-laser excitation in the spectral range 1.4-3.6 eV is obtained by measuring an m-plane-oriented ZnO thin film with femtosecond (fs)-time-resolved spectroscopic ellipsometry. From the merits of the method, we can distinguish between changes in the real and the imaginary part of the DF as well as changes in birefringence and dichroism, respectively. We find pump-induced switching from positive to negative birefringence in almost the entire measured spectral range for about 1 ps. Simultaneously, weak dichroism in the spectral range below 3.0 eV hints at contributions of inter-valence-band transitions. Line-shape analysis of the DF above the band gap based on discrete... (More)

The full transient dielectric-function (DF) tensor of ZnO after UV-laser excitation in the spectral range 1.4-3.6 eV is obtained by measuring an m-plane-oriented ZnO thin film with femtosecond (fs)-time-resolved spectroscopic ellipsometry. From the merits of the method, we can distinguish between changes in the real and the imaginary part of the DF as well as changes in birefringence and dichroism, respectively. We find pump-induced switching from positive to negative birefringence in almost the entire measured spectral range for about 1 ps. Simultaneously, weak dichroism in the spectral range below 3.0 eV hints at contributions of inter-valence-band transitions. Line-shape analysis of the DF above the band gap based on discrete exciton, exciton-continuum, and exciton-phonon-complex contributions shows a maximal dynamic increase in the transient exciton energy by 80 meV. The absorption coefficient below the band gap reveals an exponential line shape attributed to Urbach-rule absorption mediated by exciton-longitudinal-optic-phonon interaction. The transient DF is supported by first-principles calculations for 1020cm-3 excited electron-hole pairs in ideal bulk ZnO.

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type
Contribution to journal
publication status
published
subject
in
Physical Review Research
volume
3
issue
1
article number
013246
publisher
American Physical Society
external identifiers
  • scopus:85115906171
ISSN
2643-1564
DOI
10.1103/PhysRevResearch.3.013246
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2021 authors.
id
a6a5b443-09a0-4aaa-9757-0a39d7f7809f
date added to LUP
2022-04-19 14:40:41
date last changed
2024-04-20 13:44:11
@article{a6a5b443-09a0-4aaa-9757-0a39d7f7809f,
  abstract     = {{<p>The full transient dielectric-function (DF) tensor of ZnO after UV-laser excitation in the spectral range 1.4-3.6 eV is obtained by measuring an m-plane-oriented ZnO thin film with femtosecond (fs)-time-resolved spectroscopic ellipsometry. From the merits of the method, we can distinguish between changes in the real and the imaginary part of the DF as well as changes in birefringence and dichroism, respectively. We find pump-induced switching from positive to negative birefringence in almost the entire measured spectral range for about 1 ps. Simultaneously, weak dichroism in the spectral range below 3.0 eV hints at contributions of inter-valence-band transitions. Line-shape analysis of the DF above the band gap based on discrete exciton, exciton-continuum, and exciton-phonon-complex contributions shows a maximal dynamic increase in the transient exciton energy by 80 meV. The absorption coefficient below the band gap reveals an exponential line shape attributed to Urbach-rule absorption mediated by exciton-longitudinal-optic-phonon interaction. The transient DF is supported by first-principles calculations for 1020cm-3 excited electron-hole pairs in ideal bulk ZnO.</p>}},
  author       = {{Herrfurth, O. and Richter, S. and Rebarz, M. and Espinoza, S. and Zúñiga-Pérez, J. and Deparis, C. and Leveillee, J. and Schleife, A. and Grundmann, M. and Andreasson, J. and Schmidt-Grund, R.}},
  issn         = {{2643-1564}},
  language     = {{eng}},
  month        = {{03}},
  number       = {{1}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review Research}},
  title        = {{Transient birefringence and dichroism in ZnO studied with fs-time-resolved spectroscopic ellipsometry}},
  url          = {{http://dx.doi.org/10.1103/PhysRevResearch.3.013246}},
  doi          = {{10.1103/PhysRevResearch.3.013246}},
  volume       = {{3}},
  year         = {{2021}},
}