Atomic force microscope (AFM) is very useful in nano-scale force measurement. Lateral force is typically used in nanoscratch and surface friction measurement based on AFM. As one of the most important parameters to obtain lateral force, the lateral spring constant of AFM cantilever probe is of great significance and needs to be quantitative calibrated. Lateral torsion and lateral force of the cantilever are two parameters need to be measured in lateral spring constant calibration. In this article, we develop a calibration system and introduce a calibration method using an AFM head and an electromagnetic balance. An aluminium column with a known angel on top is placed on the weighing pan of the balance. The cantilever is precisely positioned in the AFM head, then approaches and bends on the aluminium column. During this procedure, the bending force and the lateral torsion of the cantilever are synchronously measured by the balance and an optical lever system, respectively. Then the lateral spring constant is calculated with a formula. By using this method, three kinds of rectangular cantilever are calibrated. The relative standard deviations of the calibration results are smaller than 2%.
Vibration isolation system is a prerequisite to achieve high resolution picture using scanning tunnel microscope (STM). The principle of spring damping isolation, staked flat-elastomer isolation, pneumatic isolation, and sandbox damping isolation is introduced. The relationship between resonant frequency of the isolation and the effect is presented. The four resonant frequencies are calculated through Finite Element Analysis (FEA). The four vibration isolations is designed and optimized according to the analysis. The experimental results show that spring damping isolation has the best effect and a transfer ratio of
10-6(120dB) can be obtained.