Gating individual nanotubes and crosses with scanning probes

Atomic force microscopy tips are used to apply point-like local gates to manipulate the electrical properties of individual single-walled carbon nanotubes (SWNT) contacted by Ti electrodes. Depleting a semiconducting SWNT at a local point along its length leads to orders of magnitude decrease of the nanotube conductance, whereas local gating to metallic SWNTs causes no change in the conductance of the system. These results shed light into gating effects on metal-tube contacts. Electrical properties of SWNT crosses are also investigated. Scanning-probe gating is used to identify the metallic or semiconducting nature of the nanotube components in the crosses. (C) 2000 American Institute of Physics. [S0003-6951(00)03513-0].