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O: Fachverband Oberflächenphysik

O 90: Semiconductor Substrates

O 90.3: Talk

Friday, March 15, 2013, 11:00–11:15, H45

Ultra-thin ZnO films on metal substrates from first principle — •Bjoern Bieniek, Yong Xu, Patrick Rinke, and Matthias Scheffler — Fritz-Haber-Institut der MPG, Berlin, Germany

In the context of catalysis and hybrid inorganic/organic systems, metal supported ultra-thin ZnO films can be used to model catalysts or ZnO surfaces. By means of density-functional theory (DFT - PBE and the hybrid functional HSE) we investigate the structure of ultra-thin ZnO on the (111) surfaces of Ag, Cu, Pd and Pt. In contrast to the bulk, the free-standing ZnO mono-layer adopts a graphene-like structure [1]. We find that this flat structure prevails on the metal substrates and obtain coincidence structures in good agreement with experiment [2, 3]. The influence of O₂ and H₂ environments is investigated with ab-initio thermo-dynamics [4] and surface phase diagrams are presented. Zn- and O-point defects are stabilized in the mono-layer by the substrates that would not be present in the freestanding ZnO mono-layer. With decreasing nobility of the metal substrate, the stability of defects, in particular inter-facial O, increases and the corrugation of the film becomes more pronounced. With increasing H₂ partial pressure sparse ring structures occur in Zn poor conditions. Metal supported ultra-thin ZnO films therefore do not resemble conventional ZnO surfaces and should be regarded as distinct nano-systems in their own right. [1] Z. C. Tu and X. Hu, PRL 94, 035434 (2006) [2] C. Tusche et al. PRL 99, 026102 (2007) [3] G. Weirum et al. J. Phys. Chem. C, 114 (2010) [4] K. Reuter and M. Scheffler, PRB 68, 045407 (2003)