Scanned probe microscopy of electronic transport in carbon nanotubes

We use electrostatic force microscopy and scanned gate microscopy to probe the conducting properties of carbon nanotubes at room temperature. Multiwal led carbon nanotubes are shown to be diffusive conductors, while metallic s ingle-walled carbon nanotubes are ballistic conductors over micron lengths. Semiconducting single-walled carbon nanotubes are shown to have a series o f large barriers to conduction along their length. These measurements are a lso used to probe the contact resistance and locate breaks in carbon nanotu be circuits.