Synthesis of ultrathin semiconducting iron silicide epilayers on Si(1 1 1) by high-temperature flash |
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Authors: | I. Goldfarb |
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Affiliation: | Department of Solid Mechanics, Materials and Systems, and University Research Institute for Nanoscience and Nanotechnology, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel |
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Abstract: | In this work ultrathin iron silicide epilayers were obtained by the reaction of iron contaminants with the Si(1 1 1) substrate atoms during high-temperature flash. After repeated flashing at about 1125 °C, reflection high-energy electron diffraction indicated silicide formation. Scanning tunneling microscopy revealed highly ordered surface superstructure interrupted, however, by a number of extended defects. Atomic-resolution bias-dependent imaging demonstrated a complex nature of this superstructure with double-hexagonal symmetry and (2√3×2√3)-R30° periodicity. Among the possible candidate phases, including metastable FeSi2 with a CaF2 structure and FeSi1+x with a CsCl structure, the best match of the interatomic distances to the measured 14.4 Å × 14.4 Å unit cell dimensions pointed to the hexagonal Fe2Si (Fe2Si prototype) high-temperature phase. The fact that this phase was obtained by an unusually high-temperature flash, and that neither its reconstruction nor its semiconducting band-gap of about 1.0 ± 0.2 eV (as deduced form the I-V curves obtained by scanning tunneling spectroscopy) has ever been reported, supports such identification. Due to its semiconducting properties, this phase may attract interest, perhaps as an alternative to β-FeSi2. |
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Keywords: | Epitaxy Silicides Scanning tunneling microscopy Scanning tunneling spectroscopies Surface structure, morphology, roughness, and topography Surface electronic phenomena (work function, surface potential, surface states, etc.) Semiconducting surfaces |
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