Low-temperature conductive tip scanning measurements of single walled carbon nanotubes.

We have built a low-temperature atomic force microscope (AFM) that fits inside a 38 mm bore cryostat. The scanning probe is attached to a quartz tuning fork, and a frequency shift is used as the feedback signal. By using a conductive tip we can locally tunnel into single walled carbon nanotubes grown on a non-conducting (SiO2) substrate. The nanotubes are contacted by a metal grid *electrode* evaporated on top of the sample. The tip is used as a second, movable contact. We measure the nanotube conduction as a function of the tip position and the gate voltage.