The effects of crystallinity and catalyst dynamics on boron carbide nanospring formation

摘要

The formation of helical nanowires—nanosprings—of boron carbide have been observed and a growthmechanism, based on the work of adhesion of the metal catalyst and the tip of the nanowire, developed.The model demonstrates that the asymmetry necessary for helical growth is introduced when thefollowing conditions are met:(1) The radius of the droplet is larger than the radius of the nanowire, and(2) The center of mass of the metal droplet is displaced laterally from the central axis of thenanowire.Furthermore, this model indicates that only amorphous nanowires will exhibit this unique form of growthand that in monocrystalline nanowires it is the crystal structure that inhibits helical growth. Highresolutiontransmission electron microscopy and electron diffraction has been used to compare thestructure of both amorphous and crystalline nanowires.