Abstract:Atomic force microscopy (AFM) is an important tool for observing and manipulating samples at micronanometer scale. Compared with traditional contacting mode and tapping mode AFMs, the nonresonant tapping mode AFM has got wide applications due to its high accuracy control force and the ability to acquire multiple mechanical characteristics simultaneously. In this paper, adopting the method based on combining the background subtraction and synchronization algorithm, a homebuilt nonresonant tapping mode AFM is built. A general noise simulation model is established for the position detection circuit, the position detection circuit noise is optimized, so that the precision of the minimum controllable force is improved, which makes the minimum controllable force smaller than 50 pN. The morphology characterization of the standard silicon lattice was performed to verify the imaging performance of the system. And the characterization of various mechanical properties of composite materials, such as morphology, adhesion force and deformation was carried out to verify the effectiveness of the system and the imaging method.