Deep vs shallow nature of oxygen vacancies and consequent n -type carrier concentrations in transparent conducting oxides

J. Buckeridge, C. R.A. Catlow, M. R. Farrow, A. J. Logsdail, D. O. Scanlon, T. W. Keal, P. Sherwood, S. M. Woodley, A. A. Sokol, Aron Walsh

Research output: Contribution to journalArticle

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Abstract

The source of n-type conductivity in undoped transparent conducting oxides has been a topic of debate for several decades. The point defect of most interest in this respect is the oxygen vacancy, but there are many conflicting reports on the shallow versus deep nature of its related electronic states. Here, using a hybrid quantum mechanical/molecular mechanical embedded cluster approach, we have computed formation and ionization energies of oxygen vacancies in three representative transparent conducting oxides: In2O3,SnO2, and ZnO. We find that, in all three systems, oxygen vacancies form well-localized, compact donors. We demonstrate, however, that such compactness does not preclude the possibility of these states being shallow in nature, by considering the energetic balance between the vacancy binding electrons that are in localized orbitals or in effective-mass-like diffuse orbitals. Our results show that, thermodynamically, oxygen vacancies in bulk In2O3 introduce states above the conduction band minimum that contribute significantly to the observed conductivity properties of undoped samples. For ZnO and SnO2, the states are deep, and our calculated ionization energies agree well with thermochemical and optical experiments. Our computed equilibrium defect and carrier concentrations, however, demonstrate that these deep states may nevertheless lead to significant intrinsic n-type conductivity under reducing conditions at elevated temperatures. Our study indicates the importance of oxygen vacancies in relation to intrinsic carrier concentrations not only in In2O3, but also in SnO2 and ZnO.

Original languageEnglish
Article number054604
JournalPhysical Review Materials
Volume2
Issue number5
DOIs
Publication statusPublished - 2018 May 25

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Oxygen vacancies
Oxides
Carrier concentration
conduction
oxides
oxygen
Ionization potential
conductivity
oxygen supply equipment
Electronic states
ionization
orbitals
Point defects
Conduction bands
Vacancies
void ratio
energy of formation
point defects
conduction bands
Defects

All Science Journal Classification (ASJC) codes

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

Cite this

Buckeridge, J. ; Catlow, C. R.A. ; Farrow, M. R. ; Logsdail, A. J. ; Scanlon, D. O. ; Keal, T. W. ; Sherwood, P. ; Woodley, S. M. ; Sokol, A. A. ; Walsh, Aron. / Deep vs shallow nature of oxygen vacancies and consequent n -type carrier concentrations in transparent conducting oxides. In: Physical Review Materials. 2018 ; Vol. 2, No. 5.
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Buckeridge, J, Catlow, CRA, Farrow, MR, Logsdail, AJ, Scanlon, DO, Keal, TW, Sherwood, P, Woodley, SM, Sokol, AA & Walsh, A 2018, 'Deep vs shallow nature of oxygen vacancies and consequent n -type carrier concentrations in transparent conducting oxides', Physical Review Materials, vol. 2, no. 5, 054604. https://doi.org/10.1103/PhysRevMaterials.2.054604

Deep vs shallow nature of oxygen vacancies and consequent n -type carrier concentrations in transparent conducting oxides. / Buckeridge, J.; Catlow, C. R.A.; Farrow, M. R.; Logsdail, A. J.; Scanlon, D. O.; Keal, T. W.; Sherwood, P.; Woodley, S. M.; Sokol, A. A.; Walsh, Aron.

In: Physical Review Materials, Vol. 2, No. 5, 054604, 25.05.2018.

Research output: Contribution to journalArticle

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AU - Catlow, C. R.A.

AU - Farrow, M. R.

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AU - Walsh, Aron

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