Characteristic capacitance in an electric force microscope determined by using sample surface bias effect

A method to determine the dependence of characteristic capacitance of an electric force microscopy tip on tip-sample separation is presented. It is demonstrated that by introducing sufficient voltage to the sample surface, the first derivative of the characteristic capacitance for tip-sample complex could be obtained and, subsequently, the characteristic capacitance versus tip-sample separation could be determined. In addition, the effective charge position on the tip relative to sample surface could also be identified.