Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 109: Heterogeneous Catalysis on Metal Oxides

O 109.9: Talk

Thursday, March 19, 2020, 17:00–17:15, TRE Phy

Revisiting the high temperature oxidation of Ni₃Al(111) by in situ STM — •Tim Kratky¹, Xinzhou Ma^1,2, and Sebastian Günther¹ — ¹TUM, Dept. Chemie, Lichtenbergstr. 4, D-85748 Garching — ²Foshan University, Materials Science and Energy Engineering, CN-528000 Guangdong

The Ni₃Al(111) surface was characterized during oxidation within the temperature range of 690-800 K by in situ scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and auger electron spectroscopy (AES). Surface aluminum oxide formation is observed. Above 790 K, the known (√67×√67)R12.2^∘ double layer oxide grows, which consists of two Al–O layers. Oxygen dosing at the lower temperature of 740±10 K leads to a single layer oxide showing a (7×7) moiré pattern. Surprisingly, when lowering the temperature below 720 K during oxygen exposure, a so far unknown bilayer oxide arises. At temperatures close to 720 K, the 2nd layer is ordered and a novel diffraction pattern with a (4√3× 4√3)R30^∘ unit cell is observed with its hexagonal O lattice aligned to the support. Below 700 K, the 2nd oxide layer is still formed ontop of the single layer oxide but in a disordered state so that the LEED pattern of the single layer oxide with a (7× 7) moiré unit cell is observed again. Thus, the confusing fact arises that the (7× 7) LEED pattern may originate from both, a single- or a low temperature double layer oxide.