Y-junction carbon nanotubes grown by in situ evaporated copper catalyst

Y-junction carbon nanotubes have been grown by hot-filament chemical vapor deposition for which a gas mixture of acetone and hydrogen was fed and in s itu evaporated copper was supplied. Transmission electron microscopy images reveal that? two of three branching angles around the Y-junction are obtus e (>90 degrees) while the other is sharp (<90<degrees>). The sharp branchin g angles ranging between 50 degrees and 80 degrees are nearly twice the ben ding angles of simple bend junctions. This indicates that the Y-junction ca n be presented in structure as a combination of two bend junctions. An atom ic configuration involving six heptagons on the three saddle surfaces is pr oposed to understand the topological structure of the observed Y-junction c arbon nanotubes. (C) 2001 Elsevier Science B.V. All rights reserved.