In this work we report a comprehensive experimental and computational study of the dynamical behavior of the tapping mode atomic force microscope (AFM) probe in interaction with the force field of a sample surface. To address the nonlinear nature of the probe dynamics, we apply describing function method. We established that the corner frequency of the low pass describing function of the probe is sensitive to the modulation amplitude and is generally higher than predicted by linear — force gradient — approximation. We show that large tip apex radii and high values of surface Young’s moduli can introduce a resonant amplitude transfer, which could lead to image distortion and system instabilities. We demonstrate that the oscillating amplitude of the probe far from the surface and during imaging, and the ratio of these two (setpoint) have an influence on the describing function of the probe similar to that of the quality factor. Accordingly, expert control of these parameters is as effective as active $Q$ control in improving the imaging bandwidth of the tapping mode AFM.

• Received 15 June 2005

DOI:https://doi.org/10.1103/PhysRevB.73.155403