SRC Users' Meeting - Synchrotron Radiation Center - University of ...

ELECTRONIC PROPERTIES OF MN-SILICIDE ON SI(111)
J. J. Paggel, K. Schwinge, G. Ctistis, U. Deffke, and P. Fumagalli
Institut für Experimentalphysik, Freie Universität Berlin, Germany
T. Miller and T.-C. Chiang
Department of Physics, University of Illinois at Urbana-Champaign, IL
and
Frederick-Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, IL
The electron spin as new degree of freedom in electronics is widely discussed. One
central problem is spin-injection into the semiconductor material, i.e. the transfer of the spinpolarization
from the magnetic electrode into the semiconductor. It is generally believed that
structural disorder at the interface will lower the injection efficiency. In order to achieve high
spin-polarization in the semiconductor, epitaxial, magnetic films on semiconductors are therefore
sought after.
Mn – in its conventional antiferromagnetic -phase – might be a promising candidate for
magnetic films on silicon. Its fcc-phase is lattice matched to Si. There is even a large probability
for Mn to be ferromagnetic at RT in this phase. Growing Mn-films on Si(111) yields epitaxial
films with six-fold symmetry. Auger electron spectroscopy indicates a large Si-content of the
films, maybe even a Si surface layer. RHEED and STM indicate closed films of good quality.
The nature of these films could not be revealed using our laboratory experiments. Photoelectron
spectroscopy experiments, reported here, identify the film as metallic Mn-silicide. The bonding
character between Mn and Si is largely covalent. The Si2p core-level from the silicide is very
simple and shows a striking similarity to the core-level of the famous Si(111)-(77)
reconstruction, turning the interest from potential application of the films to basic research, as the
electronic properties of the Si(111)-(77) are still under debate. The Si(111)-(77) reconstruction
shows at least two nearly dispersionless surface states, associated with adatoms, which are also
identified as origin for the prominent surface core-level of the Si(111)-(77) reconstruction. The
Si2p core-level from the silicide shows a similar surface component, such that an adatom surface
state was expected. The latter has not been found yet.
This work was funded by the Deutsche Forschungsgemeinschaft through SFB 290 and
grant Pa661/5-1, the U.S. National Science Foundation (grant DMR-02-03003), the U.S.
Department of Energy, Division of Materials Sciences (grant DEFG02-91ER45439), and the
Petroleum Research Fund, administered by the American Chemical Society. The Synchrotron
Radiation Center is supported by the National Science Foundation under grant DMR-00-84402.