Morphology of germanium nanowires grown in presence of B ₂H ₆

We study the Au-catalyzed chemical vapor growth of germanium (Ge) nanowires in the presence of di-borane (B2 H6), serving as doping precursor. Our experiments reveal that, while undoped Ge nanowires can be grown epitaxially on Si(111) substrates with very long wire lengths, the B2 H6 exposure renders the Ge nanowires significantly tapered. As we describe here, this peculiar morphology stems from the combination of the acicular, one-dimensional nanowire growth and a dramatically enhanced, B-induced conformal Ge deposition. The combination of acicular and conformal Ge growth mechanisms results in cone-shaped Ge nanostructures. © 2006 American Institute of Physics.