Unconventional roles of metal catalysts in chemical-vapor syntheses of single-crystalline nanowires

Abstract

In this invited contribution at the 29th International Conference on the Physics of semiconductors (ICPS 2008), we review two examples of solid-catalytic nanowire (NW) growth in parallel comparisons to the NW growth from the eutectic liquid catalyst. First, we demonstrated the Cu-catalyzed Ge NW growth using GeH4 vapor precursor at 200 °C, which is far below the Cu-Ge eutectic temperature of 644 °C, with a relatively uniform diameter distribution directly templated from that of the catalysts. We provide evidence that the formation of solid Cu3 Ge catalysts and Ge diffusion across the catalysts are responsible for such low-temperature growth of Ge NWs in a size-deterministic manner. Second, we show the spontaneous silicidation of NiSix NWs on continuous Ni bulks using SiH4 vapor precursor at 400 °C. This growth is particularly marked in that NiSi x NWs are formed in a self-organized manner without employing the nanocluster catalysts. We discuss this spontaneous growth of NiSix NWs within the frame of the nucleation kinetics in the low supersaturation limit in analogous with the earlier examples of the vapor-condensation at the low vapor pressures. © 2009 American Institute of Physics.