  We use Kelvin Force Microscopy (KFM) to study the electrostatic properties of
single-walled Carbon Nanotube Field Effect Transistor devices (CNTFETs) with
backgate geometry at room temperature. We show that KFM maps recorded as a
function of the device backgate polarization enable a complete phenomenological
determination of the averaging effects associated with the KFM probe side
capacitances, and thus, to obtain KFM measurements with quantitative character.
The value of the electrostatic lever arm of the CNTFET is determined from KFM
measurements, and found in agreement with transport measurements based on
Coulomb blockade.
