Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 16: Oxide und Isolatoren I
O 16.4: Vortrag
Dienstag, 25. März 2003, 12:00–12:15, FOE/ANOR
Color center formation and metal adsorption on vicinal MgO films — •C. Tegenkamp, J. Kramer, and H. Pfnür — Institut für Festkörperphysik, Universität Hannover, Appelstrasse 2, 30167 Hannover
In this study we explored the possibility to grow MgO films
with high step density and to form color centers on step sites.
Both the formation of color centers on these MgO surfaces and the
adsorption
of Pd have been studied by means of EELS and XPS.
At first the morphology of MgO films on a Ag (1 1 19) substrate has been
investigated using SPA-LEED.
After deposition of a few monolayers of MgO, satellites appear around the
specular beam, which are attributed to
(1 1 19) facets and mosaics.
A detailed analysis of the spot positions has shown that the steps are
composed of both polar and non-polar edges.
In order to study color center formation, these vicinal MgO surfaces have
been
irradiated with electrons and the formation of several loss features in the
band gap
was examined by EELS.
In comparison with experiments on a flat MgO surface, an increase of
loss–intensities caused by color centers at
step sites was observed due to the higher step density.
The adsorption of small coverages of Pd on the disturbed surface results in
the disappearance of the loss–intensity,
therefore color centers are a preferred adsorption site for Pd atoms.
Interestingly, the first monolayer of Pd seems to wet the MgO surface and
an
oxidic species PdOx
is formed.