Amplitude Response of Single-Wall Carbon Nanotube Probes during Tapping Mode Atomic Force Microscopy:  Modeling and Experiment

Imaging of surfaces with carbon nanotube probes in tapping mode results frequently in complex behavior in the amplitude−distance curves monitored. Using molecular mechanics simulations, we calculate the force exerted on a nanotube pressed against a smooth surface as it undergoes deformation and buckling. This nonlinear force is then used in a macroscopic equation, describing the response of a damped harmonic oscillator, to predict the amplitude response of a nanotube AFM probe. Similarities between the prediction and experiment suggest that the complex amplitude response seen in the experiment may be explained by the nonlinearity in the force exerted on the nanotube and thus must not necessarily be related to the structure of the surface.