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原子力显微镜(atomic force microscope,AFM)的扫描探针、针尖以及样品组成了一个微观接触、弹性变形、相对运动和摩擦的系统.采用微尺度黏着接触理论的M-D模型,研究了微探针针尖和样品表面的弹性接触和相对运动,探究了扫描过程中能量的转换和耗散过程.推导出了无量纲的黏滑数,模拟出了不同黏滑数下的AFM侧向力信号:η<1时,AFM侧向力信号十分微弱,没有剧烈突变;η=1时,出现针尖跳跃现象(对应微观黏滑现象),但没有能量损耗;η>1时,针尖跳跃滞后加强,黏滑现象明显,并且伴随能量耗散.该无量纲参数揭示了微观黏滑现象产生的机理,统一地表示了探针刚庋、结构参数、黏着接触表面、载荷、样品形貌以及扫描参数的综合作用和影响,并与现有的AFM测试结果吻合良好.最后,提出了从AFM侧向力信号中定量提取摩擦力信号的分析方法.
The scanning probe, tip and sample of the atomic force microscope (AFM) make up a system of micro-contact, elastic deformation, relative motion and friction.Using the MD model of micro-scale adhesive contact theory, The elastic contact and relative motion of the sample surface were investigated, and the energy conversion and dissipation process in the scanning process was explored.The dimensionless number of stick-slip was deduced and the AFM lateral force signal was simulated with different stick-slip numbers: η <1 , The lateral force signal of AFM was very weak with no abrupt mutation; when η = 1, the phenomenon of pinpoint jump (corresponding to microscopic stick-slip phenomenon) appeared but there was no energy loss; when η> 1, the tip jump hysteresis was strengthened and the phenomenon of stick- , And accompanied by energy dissipation.The dimensionless parameters reveal the mechanism of microscopic stick-slip phenomena and unified the comprehensive effect and influence of probe stiffness, structural parameters, adhesive contact surface, load, sample morphology and scanning parameters , And it is in good agreement with the existing AFM test results.Finally, an analysis method of quantitatively extracting the friction signal from the AFM lateral force signal is proposed.