Real-Space Imaging of the First Stages of FeSi 2 Epitaxially Grown on Si(111): Nucleation and Atomic Structure

The first stages of the growth of iron disilicide on Si(111) have been studied with Scanning Tunnelling Microscopy. Nucleation and growth of two-dimensional, epitaxial islands of disilicide are obtained by means of a Solid Phase Epitaxy method. Atomically resolved images show that the islands present a hexagonal closed-packed symmetry and correspond to the first stage of a new metastable cubic phase of FeSi 2 which grows matching its (111) plane to the Si(111) surface. The surface of the islands shows a 2 × 2 reconstruction explained on the basis of the reduction in number of Si dangling bonds. The results allow us to visualize in the real space that metastable phases can be stabilized by heteroepitaxial growth on suitable substrates.