In-contact dynamics of atomic force microscopes

Demonstrates and explains the great impact scan parameters and cantilever properties have on the dynamics of atomic force microscopes (AFM), and hence its performance. Results show that when operating in air and in-contact with hard samples, modal damping is a strong function of contact force set-point and amplitude of disturbance, i.e. sample surface topography. Small amplitudes and large set-points result in lower damping. In addition, a large contact force can result in damage to the sample and increase friction force between probe and sample. Further, cantilevers with long probes result in pole-zero flipping possibly due to the compliance of the probe being comparable to that of the cantilever. These large changes in the dynamics of the AFM impose a challenge on its feedback system. It requires a controller that provides robust performance to ensure high-fidelity of data and reduce image artifacts. Consequently, the selection of scan parameters should be tied-in to controller parameters to potentially achieve higher level of performance.