AVS 45th International Symposium
    Surface Science Division Thursday Sessions
       Session SS-ThP

Paper SS-ThP22
Stoichiometric Phase Transition and Facetting of Low Index Fe@sub 3@Si Surfaces

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: J. Schardt, University of Erlangen-Nuernberg, Germany
Authors: J. Schardt, University of Erlangen-Nuernberg, Germany
W. Weiss, University of Erlangen-Nuernberg, Germany
W. Meier, University of Erlangen-Nuernberg, Germany
C. Polop, Universidad Autonoma de Madrid, Spain
P.L. de Andres, Universidad Autonoma de Madrid, Spain
U. Starke, University of Erlangen-Nuernberg, Germany
K. Heinz, University of Erlangen-Nuernberg, Germany
Correspondent: Click to Email
In binary compounds segregation of one of the constituents is a freqently observed phenomenon. The respective changes of the stoichiometry are often not restricted to the topmost surface region. In this line, two phases of different stoichiometry can be stabilized on the (100), (110) and (111) surfaces of Fe@sub 3@Si bulk samples. On each surface the two phases can be reversibly transformed into each other by extended annealing cycles. The stability regions of each phase and the phase transition temperatures were determined using the stoichiometric information obtained from Auger electron spectroscopy (AES) and structural fingerprints gained from spot intensity spectra, I(E)-curves, of the low-energy electron diffraction (LEED) pattern. These I(E)-curves were used for quantitative LEED structure analyses of each phase. In the low temperature regime (400° C) for all surfaces a D0@sub 3@ crystal structure can be confirmed. However, for preparation temperatures of around 600° C a restructuring of the surface region is observed. Segregation leads to a Si enrichment of the surface. This is accompanied by a structural transition to a CsCl crystal structure within the region accessible to the low-energy electrons. In addition, using LEED facetting of the (100) and (111) surfaces is observed with facets in (110) orientation which obviously is the energetically most stable plane of Fe@sub 3@Si.