  The characteristic tip_substrate capacitance is crucial for understanding the
localized electrical properties in atomic force microscopy (AFM). Since it is
highly dependent on tip geometrical features, estimation of the tip_substrate
characteristic capacitance for a given probe is very complex, involving
empirical measurements and numerical simulations. In this paper we propose a
facile approach to study the tip_substrate characteristic capacitance using AFM
force spectroscopy technique. In this scheme, an analytical expression is
considered to model the tip_sample interaction, in which the coefficients are
directly dependent on the tip_substrate capacitance. This method avoids any
complex simulation involving irregular shape of AFM tips. Additionally, it
considerably reduces amount of experimental data needed for the calculation
compared with other techniques. The work presented here also corroborates that
for tip_sample separation lower than 200 nm, the parallel plate_capacitor
approximation is not very appropriate to describe the tip_substrate capacitive
interaction, but an intermediate approximation between a sphere_plane and a
cone_plane geometry seems to be more appropriate.
