Crystal phase and growth orientation dependence of GaAs nanowires on Ni_xGa_y seeds via vapor-solid-solid mechanism

One of the challenges to utilize high performance III-V compound semiconductor nanowires (NWs) for large-scale technological applications is to control the crystal phase and growth orientation for homogenous nanowire properties. Here, we report the dependence of crystal structure and growth orientation of GaAs NWs on Ni_xGa_y seeds via vapor-solid-solid mechanism. The crystal structure of catalytic seeds is found to direct the crystal phase of NWs with cubic NiGa seeds yielding zincblende GaAs NWs while hexagonal Ni₂Ga₃ seeds producing wurtzite GaAs NWs. Furthermore, the seed/nanowire interface plane relationship would dictate the epitaxial growth orientation of NWs, which is independent of the NW diameters and growth conditions. All these suggest the importance of well-controlled phase and orientation of catalysts for the synthesis of homogenous nanowires.