Dynamic atomic force microscopy (AFM) is a standard technique for imaging and the analysis of surfaces at the nanometer scale. In order to estimate material properties from the microscope data it is important to understand the nonlinear dynamics in the tip-sample interaction. Here, the system response of a tapping-mode atomic force microscope is invstigated with numerical simulations. In the numerical model, the AFM cantilever is treated as a distributed parameter system that is capable of higher eigenmode excitation. With this multiple-degree-of-freedom (MDOF) approach the generation of higher harmonics as well as the generation of subharmonics is analysed. Under typical imaging conditions higher harmonics are generated whereas a closer approach to the specimen surface can lead to a complicated dynamics.
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