  A method to precisely calibrate the oscillation amplitude in Dynamic Scanning
Force Microscopy is described. It is experimentally shown that a typical
electronics used to process the dynamic motion of the cantilever can be
adjusted to transfer the thermal noise of the cantilever motion from its
resonance frequency to a much lower frequency within the typical bandwidth of
the corresponding electronics. Therefore, the thermal noise measured in the
in-phase ("phase") and out of phase ("amplitude") output of such an electronics
can be related to the thermal energy $kT$. If the force constant of the
cantilever is known then the oscillation amplitude can be precisely calibrated
from the thermal power measured in these signals. Based on this concept, two
procedures for the calibration of the oscillation amplitude are proposed. One
is based on simple calculation of the Root Mean Square (RMS) measured at the
outputs of the electronics used to process the dynamic motion of the
cantilever, and the other one is based on analysis of the corresponding
spectrum and the calculation of the quality factor, the resonance frequency and
the signal strength.
