Local current density detection of individual single-wall carbon nanotubes in a bundle

We have measured the local current density on individual single-wall carbon nanotubes (SWNTs) with the conducting tip of an atomic force microscope; the SWNTs make up a nanometer-scale electronic circuit on an insulating substrate. Scanning tunneling spectroscopy measurements at certain positions on a SWNT bundle show that both metallic and semiconducting nanotubes can coexist in a bundle. The approach applied in this experiment appears as a powerful technique for the investigation of the spatial variation of current density and electronic states of nanometer-scale electronic devices.