Molecular Dynamics Simulation And Dynamics Characteristic Research Of AFM Tip-sample

Micro-electromechanical systems(MEMS) is a multidisciplinary technology, MEMS dynamics research is one of the most important branch, while it is important to study on Nonlinear Dynamics of the coupled system in tip-sample system of atomic force microscope(AFM). Currently, the study of force between tip-sample system has been in exploring stage, and it had no fixed expression in tip-sample system. So according to the above problem, the main research content and the results of this article are as follows:(1) The mechanical properties of AFM between the tip-sample system was investigated. According to the molecular dynamics(MD), the molecular dynamics simulation was employed to study the tip-sample system, in our approach, the hybrid potential was used to simulate the interaction force between them and get an expression of force-distance curve. The interaction force between tip-sample system was discussed in detail when the system under different temperature and the probe tip moved at different speed, and then discussed the influence of different sample material to the interaction force of tip-sample system. The results indicated that the interaction force between tip-sample system increased sharply when the tip had 0.2 nm from the samples, however, the repelling force played a main role. At the same time, there were still some sample atoms adsorbed on the tip surface when tip contact or separated the sample under the action of surface effect.(2) Based on this expression, the dynamic model and Kinetic equation of tip-sample system were established, solved the equation of system by using multi-scale method and obtained the system frequency response function. The relationship between the natural frequency, the response amplitude, the exciting force amplitude and cubic stiffness of system and frequency response curve were discussed respectively. The effects of different sample material on the dynamical characteristic in coupled AFM system was studied by using numerical simulation study, the time history curve and phase diagrams of different locations between tip to sample were compared and the bifurcation diagram was draw when the response of tip-sample system changed under different sample parameters A. The results indicated that various periodic motions occurred in the tip-sample system, different tip and sample material of AFM had a high impact on the nonlinear dynamical characteristics of the system. In addition, it is pointed out that the reason of the system response curve was bent, and obtained the result of tip-jump is due to response curve appeared multiple values in the area of the resonance.