Speaker
Dr
Emmanuel Igumbor
(University of Pretoria)
Description
In this work we present ab-initio calculation results for the Tm3+ interstitial, vacancy-interstitial complex (VGe-Tm3+i) and substitutional (Tm3+Ge) defects as determined by using the Heyd, Scuseria, and Ernzerhof (HSE06) hybrid functional. We calculated the formation energies and the charge state transition levels of different configurations. Our results show that the Tm3+i exists in both the hexagonal and tetrahedral configuration with low formation energy. The interstitial atom is most energetically favourable at the tetrahedral site. The formation energies for the VGe-Tm3+i and Tm3+Ge were as low as 0.84 eV. The most energetically favourable defects were the VGe-Tm3+i in the axial configuration and the Tm3+Ge. The Tm3+Ge and VGe-Tm3+i introduced a single acceptor &epsilon(0/-1) charge state transition level that was positioned deep in the middle of the band gap. The majority of the levels induced by the defects under investigation were either shallow donor or acceptor level lying close to the band gap edges. The charge state thermodynamic transition levels revealed that the vacancy-complex VGe-Tm3+Ge induced shallow levels in the band gap. The VGe-Tm3+Gedisplayed evidence of a single donor level &epsilon(+1/0) and an acceptor level &epsilon(-1/-2) within the band gap. Charge state controlled metastability was exhibited by the VGe-Tm3+Ge.
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No
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No
Would you like to <br> submit a short paper <br> for the Conference <br> Proceedings (Yes / No)?
No
Primary author
Dr
Emmanuel Igumbor
(University of Pretoria)
Co-author
Prof.
Walter Meyer
(University of Pretoria)
