Fabrication of α-FeSi2 nanowhiskers and nanoblades via electron beam physical vapor deposition

Iron disilicide nanowhiskers and nanoblades are synthesized by depositing Fe onto Si(100) substrates at about 900 degrees C via electron beam physical vapor deposition. The nanostructures are determined as single crystalline alpha-FeSi2 with tetragonal lattice. The nanostructures are stable with prolong exposure under ambient condition, and no transformation towards beta-FeSi2 is detected after 2 h annealing at 500 degrees C and 800 degrees C under high vacuum condition (10(-6) mbar). The growth directions of the whiskers are found as either [001] or [100]. However, in the blades we observe grow only in [100] crystallographic direction. Changing cross-sectional shape of the alpha-FeSi2 whiskers from octagon at the root to rectangle at the upper part is observed and believed to be a result of the thermodynamic and kinetic anisotropy. SiO2 layer formed on the surface of the structures because of its lower surface energy compared to all iron oxides. By this a passivation, which prevents further oxidization, of the nanowhiskers is achieved. The alpha-FeSi2 whiskers form by root growth. (C) 2019 The Authors. Published by Elsevier Ltd.