Berlin 2024 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 49: Oxide and Insulator Interfaces I

O 49.1: Vortrag

Mittwoch, 20. März 2024, 10:30–10:45, MA 144

Structure of the Al2O3(0001) surfaceJan Balajka1, Andrea Conti1, Johanna Hütner1, Florian Mittendorfer1, Georg Kresse2, •Michael Schmid1, and Ulrike Diebold11Institute of Applied Physics, TU Wien, Austria — 2Computational Materials Physics, Universität Wien, Austria

Corundum (α-Al2O3) is the thermodynamically stable form of aluminum oxide and used in many fields of technology. Nevertheless, the structures of its surfaces have not been determined yet. Our high-quality ncAFM images of the Al2O3(0001)-(√31×√31)R±9 reconstruction, which forms after high-temperature annealing, rule out the aluminum termination proposed previously [1,2]. The surface is very similar to ultrathin alumina films, which have well-established structural models [3,4]. To determine the structure of the subsurface layers not directly imaged by ncAFM, we employed density functional theory calculations and machine-learned force fields to search the large configuration space, resulting in a lowest-energy structure that fits the experiment. DFT calculations also show that the standard model for the unreconstructed Al2O3(0001)-(1× 1) surface cannot be thermodynamically stable at any conditions. We discuss reasons for the high stability of the reconstruction.

[1] Renaud et al. Phys. Rev. Lett. 73, 1825 (1994)

[2] Lauritsen et al. Phys. Rev. Lett. 103, 076103 (2009)

[3] Kresse et al. Science 308, 1440 (2005)

[4] Schmid et al. Phys. Rev. Lett. 99, 196104 (2007)

Keywords: Aluminum oxide; non-contact AFM; density functional thory; machine learning; surface structure

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