  The dynamic behavior of AFM is studied taking into account the nonlinear
interaction forces between probe and sample. The exerted forces on the free end
of micro-beam are simulated with the third degree polynomial. The effect of
some parameters on the dynamics of AFM is studied. The results show that the
frequency response of AFM is not sensitive to the tip mass in the case of both
the sample and cantilever vibration. The effect of sample vibration is studied
in the case of in-phase and anti-phase vibration. The results show that
although the vibration amplitude of sample is very small compared to the
amplitude of cantilever, it has great effect on the resonant frequency of the
cantilever.
