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DS: Fachverband Dünne Schichten
DS 11: Thin Film Properties: Structure, Morphology and Composition (XRD, TEM, XPS, SIMS, RBS, AFM, ...): Session II
DS 11.6: Vortrag
Dienstag, 13. März 2018, 10:45–11:00, H 0111
Orientation-dependent chemistry and band-bending of Ti thin layers on polar ZnO surfaces — •Patrizia Borghetti1, Younes Mouchaal1,2, Zongbei Dai1, Gregory Cabailh1, Rémi Lazzari1, and Jacques Jupille1 — 1Sorbonne Universités, Institut des NanoSciences de Paris, F-75005, Paris, France. — 2Laboratoire de Physique des Couches Minces et Matériaux pour l'Electronique (LPCMME), Université d'Oran 1 31000, Oran, Algeria
Next to its use to create ohmic contacts, the deposition of titanium on ZnO is known to promote adhesion for noble metals in optical coatings for glazings, to enhance the gas sensor properties of ZnO and to set up resistive random access memories. However the detailed mechanism of interface reactivity and the role of the surface orientation of ZnO in terms of species profile and chemical state are not yet resolved. In the present work, orientation-dependent reactivity and band-bending are evidenced by X-ray photoemission spectroscopy upon Ti deposition (1-10 Å) on the polar ZnO(0001)-Zn and ZnO(000-1)-O surfaces [1]. On Zn-ZnO, Ti reduces ZnO to form a Ti oxide, while on O-ZnO, the deposition of Ti gives rise to the formation of a (Ti, Zn, O) compound. A similar chemistry is observed upon annealing the Ti adlayers, although with very different activation temperatures, 500 K on O-ZnO and 700 K on Zn-ZnO. Those orientation-dependent behaviours are expected to strongly affect applications relying either on thin Ti/ZnO films and partly explain why Ti/ZnO electrical contact properties are quite scattered and depend on annealing treatments and crystal orientation.
[1] P. Borghetti et al., Phys. Chem. Chem. Phys., 2017, 19, 10350.