Improved calibration method for lateral force of the cantilever deflection force sensor in atomic force microscope

Quantitative friction measurement of nano materials in atomic force microscope (AFM) requires accurate calibration method for the lateral force. An improved calibration method for the lateral force of the cantilever in AFM is presented. The calibration factor derived from the original method increased with the applied normal load, which indicates that separate calibration should be required for every given applied normal load to keep the accuracy of friction measurement. We analyze the reason for this phenomenon, and improve the original method by introducing the contact factor, which is derived from the contact stiffness between the tip and the sample, to the calculation of calibration factors. Our method makes the calculation of calibration factors under different applied normal loads be possible without repeating the calibration procedure. Comparative experiments on a silicon wafer have been done by both the two methods to validate our method..