Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 77: Oxides and insulators: Epitaxy and growth
O 77.11: Vortrag
Donnerstag, 25. März 2010, 17:30–17:45, H42
Epitaxial Europiumoxide on Ni(100) with Single Crystal Quality — •Daniel F. Förster, Jürgen Klinkhammer, Carsten Busse, Zhiwei Hu, L. Hao Tjeng, and Thomas Michely — II. Physikalisches Institut, Univ. zu Köln, Zülpicher Str. 77, 50937 Köln
EuO is one of the rare ferromagnetic semiconductors. Showing a variety of outstanding electronic properties it is e.g. an ideal candidate for spintronic systems. Growth on metal substrates gives rise to additional effects e.g. due to image charge screening or Schottky barriers. Hence the electronic structure is expected to have a different thickness dependence compared to oxide substrates. The initial growth of EuO films on Ni(100) strongly depends on the flux ratio Eu/O and the growth temperature. We use reactive molecular beam epitaxy (MBE) with a flux ratio Eu/O ≈ 3/2 to grow stoichiometric EuO(100). For two monolayer thick films grown at 450∘C in-situ scanning tunneling microscopy (STM) shows films with large monatomic flat terraces and few defects. The EuO grows quasi-pseudomorphically, hence the EuO is in-plane compressed by 3.1%. Low energy electron diffraction (LEED) measurements show the relaxation of the surface lattice constant close to the bulk value within the first 40 monolayers. 100 nm thick films grown at 320∘C and annealed at 600∘C have a RMS roughness of only 0.5 nm. The step edges are roundly shaped due to the annealing process and the LEED shows spots as sharp as for a single crystal. Ex-situ X-ray adsorption spectroscopy (XAS) was performed after capping with a 4 nm thick Al film. No signs of Eu3+ or oxygen vacancies were found, thus the EuO film is stoichiometric.