Phase transition and atomic structure of an Fe 3Si(100) single crystal surface

Abstract

The surface of Fe 3Si(100) was investigated by low-energy electron diffraction (LEED) and Auger electron spectroscopy. Three different phases were observed depending on the sample annealing temperature. Two (1×1) structures with the full 2D symmetry of the DO 3-type crystal surface can be prepared at temperatures T≤400°C and T≥680°C. The two phases exhibit different LEED spot intensities, indicating that their structures are different. In the temperature regime between 525 and 625°C only a subset of diffraction spots is visible, corresponding to a c(1×1) periodicity. In this phase obviously the chemical order of the DO 3 structure is lost in the surface region. For the low temperature (1×1) phase the LEED structure analysis favours a model consisting of a bulk-like layer stacking sequence with an additional silicon layer on top of a mixed FeSi layer.