Competing stabilization mechanism for the polar ZnO(0001)-Zn surface

G. Kresse, O. Dulub, U. Diebold

Institut für Materialphysik and Center for Computational Materials Science, Universität Wien, A-1090 Wien, Austria
Department of Physics, Tulane University, New Orleans, Louisiana 70118, U.S.A.

Phys. Rev. B 68 (2003) 245409

Density-functional calculations for the (0001)-Zn surface of wurtzite ZnO are reported. Different stabilization mechanisms, such as metallization of the surface layer, adsorption of OH groups or O adatoms, the formation of Zn vacancies, and large scale triangular reconstructions are considered. The calculations indicate that isolated Zn vacancies or O adatoms are unfavorable compared to triangular reconstructions. In the absence of hydrogen, these triangular features are stable under any realistic temperature and pressure. When hydrogen is present, the reconstruction is lifted, and hydroxyl groups stabilize the ideal otherwise unreconstructed surface. The transition between the unreconstructed hydroxyl covered surface and the triangular shaped features occurs abruptly; OH groups lift the reconstruction, but their adsorption is energetically unfavorable on the triangularly reconstructed surface.

Corresponding author: Ulrike Diebold (diebold at iap_tuwien_ac_at).

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