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Strain and stress relationships for optical phonon modes in monoclinic crystals with βGa2O3 as an example

R. Korlacki, M. Stokey, A. Mock, S. Knight, A. Papamichail, V. Darakchieva, and M. Schubert
Phys. Rev. B 102, 180101(R) – Published 12 November 2020
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Abstract

Strain-stress relationships for physical properties are of interest for heteroepitaxial material systems, where strain and stress are inherent due to thermal expansion and lattice mismatch. We report linear perturbation theory strain and stress relationships for optical phonon modes in monoclinic crystals for strain and stress situations which maintain the monoclinic symmetry of the crystal. By using symmetry group analysis and phonon frequencies obtained under various deformation scenarios from density-functional perturbation theory calculations on βGa2O3, we obtain four strain and four stress potential parameters for each phonon mode. We demonstrate that these parameters are sufficient to describe the frequency shift of the modes regardless of the stress or strain pattern which maintain the monoclinic symmetry of the crystal. The deformation potentials can be used together with experimentally determined phonon frequency parameters from Raman or infrared spectroscopy to evaluate the state of strain or stress of βGa2O3, for example, in epitaxial heterostructures.

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  • Received 27 May 2020
  • Revised 27 October 2020
  • Accepted 29 October 2020

DOI:https://doi.org/10.1103/PhysRevB.102.180101

©2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

R. Korlacki1,*, M. Stokey1, A. Mock2, S. Knight1, A. Papamichail3, V. Darakchieva3, and M. Schubert1,3,4,†

  • 1Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA
  • 2NRC Research Associateship Programs, 500 Fifth Street, Washington, DC 20001, USA
  • 3Terahertz Materials Analysis Center and Competence Center for III-Nitride Technology C3NiT–Janzén, Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping SE 58183, Sweden
  • 4Leibniz Institute for Polymer Research, Dresden D-01069, Germany

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Issue

Vol. 102, Iss. 18 — 1 November 2020

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