Wilhelmer, Christoph and Turiansky, Mark E. and Waldhor, Dominic and Cvitkovich, Lukas and Van de Walle, Chris G. and Grasser, Tibor (2025) Optical properties of vacancies in aluminum oxide (α-Al2O3) from first principles. PHYSICAL REVIEW MATERIALS, 9 (9): 096202. ISSN 2475-9953
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We employ first-principles calculations based on hybrid density functional theory to investigate the structural and optical properties of the oxygen vacancy (VO) and aluminum vacancy (VAl) in alpha-Al2O3, the most stable (corundum) phase of alumina. Our calculations facilitate the identification of experimental excitation and luminescence spectra with specific electronic transitions at the vacancy sites. The absorption line shape for excitation of an electron at VO0 to the conduction-band minimum (CBM) is in excellent agreement with the 6.1 eV band detected by optical absorption spectroscopy, and we find that the 5.9 eV absorption band is generated by an internal electron transition at VO0. We confirm that the slowly decaying 3.0 eV emission band of the F center is due to a triplet-singlet transition at VO0. Our calculations also reveal that the 4.8 eV/5.4 eV absorption and 3.8 eV emission bands assigned to the F+ center are generated by internal transitions at V +1 The line shape for the excitation of an electron from VO+1 to the CBM agrees well with an absorption band at 6.4 eV, while the recombination of an electron with VO+2 also produces luminescence around 3.8 eV, but with a considerably broader line shape. For Al vacancies, we confirm that the most prevalent configuration in alpha-Al2O3 is a split-vacancy configuration VAl,s, and we calculate migration barriers for different directions in the corundum crystal. We predict absorption and emission spectra for the excitation and recombination of an electron localized Al,s sites with the CBM. The line shapes of the two VAl configurations overlap and are considerably broader than the spectra corresponding to VO.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | FINDING SADDLE-POINTS; ELECTRONIC-STRUCTURE; OXYGEN VACANCY; F+ CENTER; CENTERS; DEFECTS; LUMINESCENCE; AL2O3; BAND; ABSORPTION |
| Subjects: | 500 Science > 530 Physics |
| Divisions: | Physics > Institute of Theroretical Physics > Chair Professor Richter > Group Klaus Richter |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 16 Jul 2026 06:54 |
| Last Modified: | 16 Jul 2026 06:54 |
| URI: | https://pred.uni-regensburg.de/id/eprint/67145 |
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