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O: Fachverband Oberflächenphysik

O 14: Clean surfaces: Metals, semiconductors, oxides and insulators I

O 14.2: Vortrag

Montag, 14. März 2011, 15:15–15:30, WIL B122

Electronic structure and thermodynamics of oxygen vacancies on (100) and (111) surfaces of MgO. — •Sergey V. Levchenko, Norina Richter, and Matthias Scheffler — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany

Polar metal oxide surfaces exhibit an increased sensitivity to the chemical environment due to major changes in surface stoichiometry driven by the requirement to compensate the surface charge. On top of such rearrangements, formation of surface point defects can greatly influence chemical properties of the surface. In this study, we employ density functional theory with HSE06 exchange-correlation functional with different values of the exchange screening parameter (including PBE as a limiting case) to calculate electronic structure and formation energies of neutral and charged O vacancies at the polar MgO(111) surface, which has been (and continues to be) a subject of extensive experimental and theoretical studies. The vacancies are calculated at the O-terminated octopolar reconstruction, which was predicted to be the most stable one for a wide range of O chemical potentials [1]. We use the ab initio atomistic thermodynamics approach [2] to estimate concentration, distribution, and charge states of the vacancies as a function of temperature, oxygen pressure, and electronic chemical potential. The properties of defects at the (111) surface are compared to the defects at the non-polar (100) termination.— [1] W. B. Zhang and B. Y. Tang, J. Phys. Chem. C 112 (2008) 3327; [2] K. Reuter and M. Scheffler, Phys. Rev. B 65, 035406 (2001); C. M. Weinert and M. Scheffler, Mat. Sci. Forum 10-12, 25 (1986)