Controlled growth of Y-junction nanotubes using Ti-doped vapor catalyst

We demonstrate a bulk process for the synthesis of Y-junction carbon nanotubes using Ti-doped Fe catalysts. It is shown that the nanotube branching can be induced or stopped at will by tuning the Ti composition in the catalyst particle that seeds the growth of nanotubes. Detailed electron microscopic studies suggest that the mechanism for the observed Y-junction formation is mediated via catalyst particle attachment on the walls of a growing MWNT, from which the branching nanotubes nucleate and grow. By controlling the Ti concentration in the precursor, cascading Y-junction series as well as quadruple junctions have been successfully synthesized, offering the possibility for interesting device applications. The simplicity and controllability of such an in-situ Y-junction fabrication technique make it an excellent source of ready-made networks for potential nanoscale devices.