【摘要】 在传统标定AFM测力系统的楔形法基础上,通过线形加载的扫描方式,得到不同载荷下AFM针尖在平面和斜面上的切向力-位移循环曲线,并进一步计算出不同载荷下的摩擦力标定系数,进而根据该系数随载荷的变化趋势,选取高载下相对稳定的数据作为最终的标定结果.结果表明,由于改进的楔形法全面考察了摩擦力标定系数随载荷的变化趋势,避免了低载标定所引入的误差,标定结果更合理.更多还原

【Abstract】 Atomic force microscopy(AFM) has become one of the most important device to perform experimental studies on nanotribology.To obtain quantitative friction force,it is needed to calibrate the force in AFM.The experimental results indicated that the load exhibited a strong effect on the calibration by the traditional wedge calibration method.The calibration factor α obtained at various load could be different from each other by one order in magnitude.The effective calibration factor can even not be obtained at very low load.The reason may be related to the failure of the assumption of the wedge calibration method,since the method assumed that the friction coefficient is independent on the variation of the normal force during the calibration process.In fact,the assumption is only effective at high load.At low load,the assumption is failure since the interfacial friction is not proportional to the load,which in turn induces the large error in the calibration process.Therefore,an improved wedge calibration method was proposed in this paper.Based on the traditional wedge calibration method,the calibration factors α corresponding to various loads were obtained by experiments.From the calibration factor versus load curve,the final calibration factor α was then determined as the relatively stable value of α at high load.Since the improved wedge calibration method investigated the variation of the calibration factors with loads, the calibration result is more reasonable than the traditional one.更多还原