"seedless" vapor-liquid-solid growth of Si and Ge nanowires: The origin of bimodal diameter distributions

We identify a previously uncharacterized vapor-liquid-solid growth mode that can produce small diameter, epitaxial 〈110〉 oriented Si and Ge nanowires (NWs). Disilane or digermane pyrolysis evolves H2 causing the monolayer thick Au/Si(111) layer between three dimensional Au seeds to dewet and form small Au islands. Under some conditions, these small islands facilitate "seedless" growth of small diameter NWs distinct from larger NWs that grow from the deposited seeds leading to a bimodal diameter distribution. We identify the precursor pressures and growth temperature regimes for which Si and Ge NW growth occurs in the absence of deposited seeds from the dewetted Au/Si(111) layer.