Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 91: Epitaxy and growth: Oxides and insulators

O 91.7: Vortrag

Donnerstag, 17. März 2011, 18:45–19:00, WIL C307

Epitaxial Polar Europium Oxide on Ir(111) — •Stefan Schumacher, Daniel F. Förster, Carsten Busse, and Thomas Michely — II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln

EuO is a ferromagnetic semiconductor with a Curie temperature of 69 K and a band gap of about 1.2 eV. We have grown submonolayer films of EuO by means of reactive molecular beam epitaxy on Ir(111). The initial growth shows atomically flat islands of polar EuO(111) as can be seen from scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). Both in STM images and LEED we see a rotational mismatch of the dense-packed rows of EuO(111) and Ir(111) of up to about 5^∘.

Using dI/dz spectroscopy and analyzing the Gundlach oscillations in scanning tunneling spectra we find a strong increase of the work function for the first polar bilayer EuO compared to bare iridium. The work function increase also gives rise to a strong reduction of the apparent height of the EuO islands in STM images. We interpret the work function increase to result from the additional surface dipole created by the polar EuO(111) surface.