Tip-gating Effect in Scanning Impedance Microscopy of Nanoelectronic   Devices
  Electronic transport in semiconducting single-wall carbon nanotubes is studied by combined scanning gate microscopy and scanning impedance microscopy (SIM). Depending on the probe potential, SIM can be performed in both invasive and non-invasive mode. High-resolution imaging of the defects is achieved when the probe acts as a local gate and simultaneously an electrostatic probe of local potential. A class of weak defects becomes observable even if they are located in the vicinity of strong defects. The imaging mechanism of tip-gating scanning impedance microscopy is discussed. 
Sergei V. Kalinin, Dawn A. Bonnell, Marcus Freitag and A.T. Johnson