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SPA-LEED & SMOKE
Spot-Analysing - Low Energy Electron Diffraction and
Surface Magneto-Optical Kerr Effect
(Dr. S. Fölsch, A. Helms, A. Riemann)
Research Fields
SPALEED is a surface-sensitive technique which utilizes the diffraction of low-energy electrons (typically 10-100 eV)
at a surface. The analysis of diffraction spot profiles yields direct information on spatial correlations at the surface,
i.e., the vertical and lateral atomic surface rouhgness (mean terrace sizes and number of atomic layers exposed to the
surface) are determined quantitatively. The high resolution of the instrument (transfer width ~1000 Å) enables an
accurate measurement of lateral lattice constants. Thus, epitaxial strain and structural features of ultrathin overlayers
can be determined with high precision. Our interest is focussed on the controlled modification of structure and
morphology of surfaces and epitaxial overlayers. In particular, we are interested in the magnetic properties of
ultrathin metal films and its interrelationship with structural and morphological features. For in situ measurements
of surface- and thin-film-magnetism the system is combined with a conventional SMOKE setup.
Current activities
Recent and current activities involve
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adsorbate-mediated manipulation of regular step arrays on vicinals [Ag/Si(100)4°]
-
uniaxially strained ferromagnetic films on highly asymmetric substrates [Fe/Cu(311)]
-
stabilization of artificial structures by pseudomorphism [bcc-Co/Cr(110)]
Experiment
The apparatus enables combined in situ measurements of structure, morphology and magnetism of ultrathin ferromagnetic
overlayers under the well-defined conditions of UHV. It features a conventional SMOKE (surface magneto-optical Kerr effect)
setup for magnetic measurements and a SPALEED instrument to determine crystallographic as well as topographic properties of
the surface or the growth front. Apart from these analytical techniques the setup is equipped with additional standard-type
surface science tools (sample preparation, chemical characterization with XPS, MBE sources).
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