Features of cantilever motion in dynamic-mode AFM

The dynamic motion of a cantilever in dynamic-mode atomic force microscopy is investigated theoretically with an elastic oscillator model of the cantilever interacting with the surface. For the tip-surface interaction, the Lennard-Jones and hard-wall models are assumed. The numerical integration of the equation of motion and the Poincare map method are used for the analysis of the lip motion. Various strange features of the tip motion are due to the extremely non-linear nature of the interaction, such as quasiperiodic oscillation and fractional resonance. In particular, the coexistence of the dynamic touching mode with the non-touching mode is revealed. The phase-frequency relation of the dynamic touching mode is obtained, and can be observed experimentally. (C) 1998 Elsevier Science B.V. All rights reserved.