Growth of inclined boron nanowire bundle arrays in an oxide-assisted vapor-liquid-solid process

In the vapor-liquid-solid process typically employed for semiconductor nanowire growth, nucleation and anisotropic crystal growth of single nanowires are achieved with generation of a solid/liquid alloy interface using metal catalysts. The nucleation and growth mechanism of nanowires may be greatly altered when a second liquid is introduced into the solid/liquid alloy interface. In this work, we demonstrate bundled boron nanowire (BNW) array growth on Au coated Si substrates by introducing a second liquid of B2O3 onto the solid (B)/liquid alloy (Au-B) interface. The BNWs in each bundle are straight but highly inclined with respect to the normal of the substrate. A study of BNW morphology and chemical elemental distribution using electron microscopy and energy dispersive x-ray spectroscopy suggested that the catalyst Au provided the nucleation site for BNW bundles while the liquid B2O3 modified the initiation of BNWs from each nucleation site, resulting in multiple initiation of the BNWs from each site.