EFFECT OF MATERIAL STIFFNESS ON INTERMODULATION RESPONSE IN DYNAMIC ATOMIC FORCE MICROSCOPY

We perform simulations and experiments on an oscillating atomic force microscope cantilever approaching a surface, where the intermodulation response of the cantilever driven with two pure harmonic tones is investigated. In the simulations, the tip and surface interact with a conservative nonlinear force, and the parameter space of approach distance and surface stiffness is ex-plored. Approach experiments are carried out on three surfaces with widely varying stiffness. Qualitative similarities between simulations and experiment can be seen, but quantitative com-parison is difficult due to the overly idealized tip-surface force model used in the simulation. NOMENCLATURE z The instantaneous tip-surface separation. z0 The equilibrium tip-surface separation. ∆z0 Change in z0 as controlled by the z piezo in experiments. f0 Resonant frequency of the fundamental bending eigenmode of the cantilever. k The spring constant of this eigenmode. Q The quality factor of the resonance. ∗Address all correspondence to this author