STM and AFM investigation of coiled carbon nanotubes produced by laser evaporation of fullerene

Carbon nanotubes were grown by the evaporation of a fullerene/Ni particle mixture in vacuum, using 532 nm laser pulses of 12–28 μJ from a Nd YAG laser. The evaporated material was deposited on a freshly cleaved graphite (HOPG) surface and the samples were investigated by scanning tunneling microscopy (STM) and AFM. In the present work, we focus on the Y-branched and coiled carbon nanotubes, the formation of which supposes the incorporation of non-hexagonal rings in the hexagonal graphitic network. The regularity of the observed coils is an indication that the incorporation of the pentagons and heptagons occurred in a very regular way. The possible atomic structure of the coiled carbon nanotubes is discussed.