Epitaxially-hyperbranched FeSi nanowires exhibiting merohedral twinning

We report the synthesis of epitaxially-hyperbranched FeSi nanowires via chemical vapor transport using FeSi₂ as the source material and I₂ as the transport agent. Scanning electron microscopy reveals that the nanowires have diameters ranging from 25 to 1000 nm, depending on the morphology. Structural characterization using electron diffraction, energy dispersive spectroscopy, and powder X-ray diffraction reveal that these nanowires are single-crystalline cubic FeSi with growth in the <110> direction. X-Ray photoelectron spectroscopy shows that the thin, amorphous coating on these nanostructures is comprised primarily of silicon oxide. Interestingly, these FeSi nanowires exhibit merohedral twinning, an uncommon type of twinning in nanostructures that cannot be observed using electron diffraction, with the (001) twin plane parallel to the <110> growth direction. Such merohedral twinning should generally be expected for all B20 silicide nanowires. In addition to nanowires, other morphologies including nanocombs, nanoflowers, and micron-sized crystals are also observed during the synthesis at various temperature zones of the growth substrates.