Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 77: Oxides and insulators: Epitaxy and growth

O 77.3: Vortrag

Donnerstag, 25. März 2010, 15:30–15:45, H42

Epitaxial growth of ultra-thin ceria films on Si(111) — •Björn Menkens¹, Jan Ingo Flege¹, Sebastian Gevers², Daniel Bruns², Joachim Wollschläger², and Jens Falta¹ — ¹Institute of Solid State Physics, University of Bremen, 28359 Bremen, Germany — ²Physics Department, University of Osnabrück, 49069 Osnabrück, Germany

Rare-earth oxides are of major interest in fundamental research due to their intriguing electronic properties, which provide strong potential for multiple applications. Ceria, e.g., is a prominent compound in catalytic converters because of its high oxygen storage capacity, which results from multiple crystallographic phases and their associated oxidation states. In this contribution, we present a growth study of epitaxial ceria films on Si(111) by chemically sensitive x-ray standing waves (XSW) and grazing-incidence x-ray diffraction (GIXRD).

Under ultrahigh-vacuum conditions only Ce₂O₃ can be observed as shown by XPS. Our results show different phases depending on the ceria film thickness. The distinction between a hexagonal phase and the bixbyite (cubic) structure for ultra-thin Ce₂O₃(111) films on Si(111) was achieved by XSW using Ce3d_5/2 and O1s photoelectrons as secondary signals and subsequent comparison with calculated Fourier components. For film thicknesses exceeding a few nanometers, their crystallinity and surface roughness were investigated by GIXRD and complemented by x-ray relectivity (XRR) measurements. Furthermore, we will discuss the influence of chlorine on ceria growth on Si(111), which acts as a passivating agent for the Si(111) surface.