Synthesis of ultrathin semiconducting iron silicide epilayers on Si(1 1 1) by high-temperature flash
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چکیده
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 p 3 2p3)-R30 periodicity. Among the possible candidate phases, including metastable FeSi2 with a CaF2 structure and FeSi1þx with a CsCl structure, the best match of the interatomic distances to the measured 14.4 A · 14.4 A 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 b-FeSi2. 2004 Elsevier B.V. All rights reserved.
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تاریخ انتشار 2004