DYNAMICS OF THE CANTILEVER IN NONCONTACT ATOMIC-FORCE MICROSCOPY

The dynamics of a cantilever in noncontact atomic force microscopy (nc -AFM) is theoretically investigated based on an elastic oscillator mod el of the cantilever interacting with the surface. As for the tip-surf ace interaction, Lennard-Jones and the hard-wall potentials are assume d. Numerical integration of the equation of motion and the Poincare ma p method are used for the analyses of the tip motion. As a result of t he extremely nonlinear nature of the interaction, various strange feat ures of the tip motion, such as quasiperiodic oscillation and fraction al resonance, are found. In particular, the coexistence of the dynamic touching mode and the nontouching mode is revealed. The phase-frequen cy relationship of the dynamic touching mode is obtained, which could be observed experimentally.