Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 37: Metal Oxide Surfaces II: Structure, Epitaxy and Growth

O 37.1: Vortrag

Dienstag, 2. April 2019, 14:00–14:15, H16

Growth and phase transitions of wurtzite CoO films on Au(111) — •Maximilian Ammon1, Sara Baumann1, Tilman Kisslinger1, Lutz Hammer1, Josef Redinger2, and M. Alexander Schneider11Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, D-91058, Germany — 2Institut für Angewandte Physik & CMS, TU Wien

The metastable wurtzite polymorph of CoO shows interesting properties, but has so far only be found as nanoparticles and islands on Au(111) [1,2]. Here we establish the wurtzite polymorph on Au(111) by a LEED-I(V) analysis, STM and DFT calculations.

Cobalt oxide films with a thickness of ∼ 3 nm are grown reactively on Au(111) at T = 280 K in UHV. STM identifies that films grown under oxygen poor conditions are closed with grain sizes around 20 nm. LEED-I(V) proves the structure to be oxygen-terminated wurtzite CoO (RP = 0.13), the structural parameters are in agreement with DFT calculations. Oxygen rich conditions lead instead to spinel Co3O4. Both polymorphs undergo distinctly different irreversible phase transitions upon annealing in UHV: wurtzite CoO is a precursor for rocksalt CoO(100) (T≥ 600 K), while spinel CoO converts above 800 K to rocksalt CoO(111). Films of a thickness 1 nm grow only in the wurtzite phase as identified by the conversion to CoO(100) and the observed lattice constant of 0.326 nm.

[1] Risbud et al., Chem. Mater. 17, 834-838 (2004)

[2] Walton et al., ACS Nano 9, 2445-2453 (2015)

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