Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 99: Semiconductor Substrates: Structure, Epitaxy and Growth
O 99.8: Vortrag
Freitag, 20. März 2015, 12:15–12:30, MA 042
Morphology of ultra-thin ZnO on Ag(111) — •Bjoern Bieniek1, Patrick Rinke1,2, Takashi Kumagai1, Shamil Shaikhutdinov1, Bo Hong Liu1, and Matthias Scheffler1 — 1Fritz Haber Institut der MPG, Berlin, Germany — 2Aalto University, Helsinki, Finland
In the context of catalysis and hybrid inorganic/organic systems, metal supported ultra-thin ZnO can be used as model systems. However, the atomic morphology of these films is not well understood [1,2,3]. To investigate the thickness and termination of ZnO adsorbed on Ag we combine experimental techniques with all-electron density-functional theory calculations performed with the FHI-aims code and the PBE functional. PBE ab initio thermodynamics calculations predict H terminated 2×1-H structures to be most stable for all film thickness and H2 pressures from low to ultra-high vacuum. However, a comparison of relative apparent height differences in calculated and measured scanning tunnelling microscopy (STM) images gives the best agreement for H- and OH-free two layer ZnO films. Further evidence for H- and OH-free unreconstructed ZnO films comes from the absence of OH peaks in infra-red spectroscopy and the comparison of measured and simulated field effect resonances (FER). We attribute this discrepancy to the ab initio thermodynamics prediction to kinetic effects such as energy barriers for the dissociation of H2 and H2O. [1] C. Tusche et al. PRL 99, 026102 (2007) [2] Y. Martynova et al., J. Cat., 301, 227-223 (2013) [3] G. Weirum et al. J. Phys. Chem. C, 114 (2010)