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O: Fachverband Oberflächenphysik

O 27: Poster Session I (Methods: Scanning probe techniques; Methods: Atomic and electronic structure; Methods: Molecular simulations and statistical mechanics; Oxides and Insulators: Clean surfaces; Oxides and Insulators: Adsorption; Oxides and Insulators: Epitaxy and growth; Semiconductor substrates: Clean surfaces; Semiconductor substrates: Epitaxy and growth; Semiconductor substrates: Adsorption; Nano- optics of metallic and semiconducting nanostructures; Electronic structure; Methods: Electronic structure theory; Methods: other (experimental); Methods: other (theory); Solutions on surfaces; Epitaxial Graphene; Surface oder interface magnetism; Phase transitions; Time-resolved spectroscopies)

O 27.46: Poster

Dienstag, 24. März 2009, 18:30–21:00, P2

Epitaxial Europiumoxide on Ni(100) — •Daniel F. Foerster, Jürgen Klinkhammer, Carsten Busse, and Thomas Michely — II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany

Stoichiometric EuO is one of the rare ferromagnetic semiconductors. Slightly Eu-rich EuO contains oxygen vacancies which cause an additional semiconductor to metal transition (SMT) with resistivity changes up to 12 orders of magnitude simultaneously with the ferromagnetic transition.

We report on the growth of EuO on Ni(100) using molecular beam epitaxy with film thicknesses ranging from below one atomic layer up to several layers. The growth process is characterised at the atomic scale by in-situ variable temperature scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). Using substrate temperatures of 350^∘C EuO films grow quasi-pseudomorphically with their [100] direction oriented along the [110] direction of Ni, whereat two Ni nearest neighbour distances fit the EuO lattice constant. In consequence this quasi-pseudomorphic EuO phase is compressed by 3.1%. Based on density functional calculations the compressed EuO must be assumed to possess a significantly higher Curie temperature compared to bulk EuO. Besides the quasi-pseudomorphic phase also EuO islands with a second epitaxial relation are observed as a minority phase of EuO films on Ni(100). This phase grows with the EuO [100] direction oriented along the [100] direction of Ni, thus being rotated 45^∘ compared to the quasi-pseudomorphic phase.