Root-like structure at the nanowire/substrate interface in GaAs nanowires

We report the observation of a root-like structure at the interface between GaAs nanowires and the (100) single-crystal GaAs substrate. These nanowires were grown via the vapor-liquid-solid mechanism using metalorganic vapor phase epitaxy. The root-like structure extends from the base of the nanowires into the substrate and has been investigated in detail using transmission electron microscopy and high-resolution electron microscopy. While the nanowires predominantly exhibit the zinc-blende type diamond cubic structure with the growth axis parallel to < 111 > and growth twins perpendicular to the growth axis, the root regions have a CdTe type orthorhombic structure that has been reported to occur in GaAs only under high-pressure conditions. (c) 2006 American Institute of Physics.