Infrared dielectric functions and Brillouin zone center phonons of

Megan Stokey, Rafał Korlacki, Matthew Hilfiker, Sean Knight, Steffen Richter, Vanya Darakchieva, Riena Jinno, Yongjin Cho, Huili Grace Xing, Debdeep Jena, Yuichi Oshima, Kamruzzaman Khan, Elaheh Ahmadi, Mathias Schubert

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

We determine the anisotropic dielectric functions of rhombohedral α-Ga2O3 by far-infrared and infrared generalized spectroscopic ellipsometry and derive all transverse optical and longitudinal optical phonon mode frequencies and broadening parameters. We also determine the high-frequency and static dielectric constants. We perform density functional theory computations and determine the phonon dispersion for all branches in the Brillouin zone, and we derive all phonon mode parameters at the Brillouin zone center including Raman-active, infrared-active, and silent modes. Excellent agreement is obtained between our experimental and computation results as well as among all previously reported partial information from experiment and theory. We also compute the same information for α-Al2O3, the binary parent compound for the emerging alloy of α-(AlxGa1−x)2O3, and use results from previous investigations [Schubert, Tiwald, and Herzinger, Phys. Rev. B 61, 8187 (2000)10.1103/PhysRevB.61.8187] to compare all properties among the two isostructural compounds. From both experimental and theoretical investigations, we compute the frequency shifts of all modes between the two compounds. Additionally, we calculate overlap parameters between phonon mode eigenvectors and discuss the possible evolution of all phonon modes into the ternary alloy system and whether modes may form single-mode or more complex mode behaviors.

Original languageEnglish (US)
Article number014601
JournalPhysical Review Materials
Volume6
Issue number1
DOIs
StatePublished - Jan 2022
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Physics and Astronomy (miscellaneous)

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