Orientation-dependent chemistry and band-bending of Ti on polar ZnO surfaces

Orientation-dependent reactivity and band-bending are evidenced upon Ti deposition (1-10 Å) on polar ZnO(0001)-Zn and ZnO(0001[combining macron])-O surfaces. At the onset of the Ti deposition, a downward band-bending was observed on ZnO(0001[combining macron])-O while no change occurred on ZnO(0001)...

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Published in:Physical chemistry chemical physics : PCCP 2017, Vol.19 (16), p.10350-10357
Main Authors: Borghetti, Patrizia, Mouchaal, Younes, Dai, Zongbei, Cabailh, Gregory, Chenot, Stéphane, Lazzari, Rémi, Jupille, Jacques
Format: Article
Language:English
Subjects:
Augers
Chemical Physics
Chemical Sciences
Deposition
Inorganic chemistry
or physical chemistry
Physics
Surface chemistry
Theoretical and
Titanium
Titanium compounds
Titanium dioxide
Zinc
Zinc oxide
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Summary:Orientation-dependent reactivity and band-bending are evidenced upon Ti deposition (1-10 Å) on polar ZnO(0001)-Zn and ZnO(0001[combining macron])-O surfaces. At the onset of the Ti deposition, a downward band-bending was observed on ZnO(0001[combining macron])-O while no change occurred on ZnO(0001)-Zn. Combining this with the photoemission analysis of the Ti 2p core level and Zn L (L )M M Auger transition, it is established that the Ti/ZnO reaction is of the form Ti + 2ZnO → TiO + 2Zn on ZnO(0001)-Zn and Ti + yZnO → TiZn O + (y - x)Zn on ZnO(0001[combining macron])-O. Consistently, upon annealing thicker Ti adlayers, the metallic zinc is removed to leave ZnO(0001)-Zn surfaces covered with a TiO -like phase and ZnO(0001[combining macron])-O surfaces covered with a defined (Ti, Zn, O) compound. Finally, a difference in the activation temperature between the O-terminated (500 K) and Zn-terminated (700 K) surfaces is observed, which is tentatively explained by different electric fields in the space charge layer at ZnO surfaces.
ISSN:1463-9076
1463-9084
DOI:10.1039/c6cp08595d