Stoichiometric reconstruction of the Al₂O₃(0001) surface

J. I. Hütner, A. Conti, D. Kugler, F. Mittendorfer, G. Kresse, M. Schmid, U. Diebold, J. Balajka

Institut für Angewandte Physik, TU Wien, 1040 Wien, Austria
Faculty of Physics, University of Vienna, 1090 Vienna, Austria

Science 385 (2024) 1241-1244

Macroscopic properties of materials stem from fundamental atomic-scale details, yet for insulators, resolving surface structures remains a challenge. We imaged the basal (0001) plane of α-aluminum oxide (α-Al₂O₃) using noncontact atomic force microscopy with an atomically defined tip apex. The surface formed a complex (√31 × √31)R±9° reconstruction. The lateral positions of the individual oxygen and aluminum surface atoms come directly from experiment; we determined with computational modeling how these connect to the underlying crystal bulk. Before the restructuring, the surface Al atoms assume an unfavorable, threefold planar coordination; the reconstruction allows a rehybridization with subsurface O that leads to a substantial energy gain. The reconstructed surface remains stoichiometric, Al₂O₃.

Corresponding author: Jan Balajka (balajka).

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This manuscript is also available at arXiv.org.