原子力显微镜在轻敲模式下的动力学模型

基于Hamaker假设、Lennard-Jones势能定律及经典弹性理论建立了一种新型的球体与平面黏着接触的弹性模型，该模型显示黏着力在原子力显微镜(AFM)针尖趋近和撤离样品表面，即加载和卸载的两个过程中存在黏着滞后现象，表明了AFM在轻敲工作模式中存在能量耗散.同时，根据所建的黏着接触弹性模型，建立了AFM在轻敲工作模式下的动力学模型，研究了AFM在轻敲工作模式下的振动幅度、相位差及耗散功率随针尖与样品表面间距的变化规律，仿真结果与现有的实验结果相一致.

Dynamic model of atomic force microscopy in tapping-mode

The theoretical model about energy dissipation of atomic force microscopy (AFM) in tapping-mode has great significance for the investigation of the dynamic response of AFM tip influenced by the adhesive force. Based on the Hamaker hypotheses and the Lennard-Jones potential and elastic theory, a novel elastic model is established for adhesive contact between a sphere and a plane. The model shows that the variation of the adhesive force with the distance in the loading process is different from that in the unloading process, i.e., an adhesive hysteresis, which is the indication of energy dissipation of AFM, is engendered in the tapping-mode. On the basis of the adhesive model, the dynamic model of AFM in tapping-mode is established to investigate the variations of the amplitude, phase shift and energy dissipation with the distance between AFM tip and the sample surface. The results obtained by the dynamic model are in agreement with the experimental results available.