Exploring the Effect of Plasticity on the Phase Imaging of TM-AFM Through Molecular Dynamics Simulations

In the tapping-mode atomic force microscope (TM-AFM), the probe tip continuously taps the sample surface, which may cause plastic deformation of the sample and result in energy dissipation. The energy dissipation of the probe is closely related to the scanned phase image. To quantify the energy dissipation due to plastic indentations of the sample, this study utilized a combination of molecular dynamics (MD) simulations and experiments on single-crystal copper samples, including multiple nano-indentation tests. The energy dissipation of the probe due to the plastic deformation of the sample was calculated by integrating the hysteresis curve of the indentation depth versus the force applied to the indenter. The simulation results are in good agreement with the experimental ones. Both sets of results have demonstrated that the plastic energy dissipation decreases as the number of indentations increases, and eventually the energy of the probe tends to stabilize. This equilibrium energy dissipation is associated with other dissipation mechanisms. Furthermore, it was observed that, after hundreds of taps, the dissipated energy of plastic deformation could be ignored, implying that the scanned image may not reflect the plasticity information of the sample after multiple taps of the probe on the sample surface for scanning.