Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 89: Oxides and Insulator Surfaces II
O 89.10: Vortrag
Donnerstag, 10. März 2016, 17:30–17:45, H4
SMSI effect of a non-reducible oxide: ZrO2/metal inverse model catalysts — •Michael Schmid, Peter Lackner, Joong-Il J. Choi, and Ulrike Diebold — Institut f. Angewandte Physik, TU Wien, Vienna, Austria
Many oxide-supported metal catalysts exhibit the so-called SMSI (strong metal-support interaction) effect, where the metal gets overgrown by an ultrathin oxide layer under reducing conditions [1,2]. This effect is usually limited to reducible oxides, and the ultrathin oxide is substoichiometric. We have deposited few-layer ZrO2 films on Pt and Rh(111) surfaces and find dewetting upon annealing to high temperatures in oxygen, i.e., between the oxide islands the bare metal surface gets uncovered. Annealing in ultrahigh vacuum instead leads to a structure akin to Stranski-Krastanov growth, i.e., oxide islands with the metal in between covered by an ultrathin oxide, as in SMSI systems. We identify this ultrathin oxide as an essentially stoichiometric ZrO2 trilayer [3], thus the reason for the SMSI effect observed must be different from the usual variation of oxide stoichiometry. We propose a new mechanism for the SMSI effect, which is alloying between Zr and the metal, modifying the metal-oxide bonding.
[1] Tauster, Fung, Baker, Horsley, Science 211, 1121 (1981).
[2] Dulub, Hebenstreit, Diebold, Phys. Rev. Lett. 84, 3646 (2000).
[3] Antlanger et al., Phys. Rev. B 86, 035451 (2012).