Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 56: Oxide Surfaces I

O 56.4: Vortrag

Mittwoch, 13. März 2013, 16:45–17:00, H45

Growth of ultrathin samaria films on Pt(111) studied by LEED and STM — •J.H. Jhang¹, A. Schaefer¹, W. Cartas², J.F. Weaver², and M. Bäumer¹ — ¹Institute for Applied and Physical Chemistry, University of Bremen, Germany — ²Department of Chemical Engineering, University of Florida, USA

Samaria has been considered as a highly selective catalyst for oxidative coupling of methane (OCM). It also exhibits catalytic activity for dehydration reactions, e.g. the decomposition of 2-propanol. Heterocatalytic reactions take place on the surface of catalysts, thus the selectivity and activity of oxide catalysts strongly depend on surface defects, surface structures, and also oxygen storage and release capabilities. While other rare earth oxides like ceria have been studied intensively, detailed surface science studies on samaria are still lacking. In this contribution we report an investigation of ultrathin samaria films grown on a Pt(111) substrate. Samaria films were prepared by physical vapor deposition (PVD) of Sm metal in O₂ (p = 5 x 10⁻⁷ mbar) at 600 K substrate temperature, then post-annealed in O₂ at 1000 K in order to obtain well-ordered samaria structures. The well-ordered structures have been characterized via low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Both LEED and STM results reveal a lattice parameter of the samaria films close to the (111) surface orientation of C-type Sm₂O₃. Annealing treatments in UHV caused significant topographic changes to the films, accompanied by the formation of a cubic phase in (001) orientation, most likely SmO, due to partial reduction.