Design Of Hardware System And Experiments For Multi-mode AFM

In order to improve the characteristics of dynamic AFM, a new kind of surfacemeasurement method is put forward based on the higher-order resonance characteristicsof the silicon cantilever. Based on the new method, a new set of multi-mode AFMsystem is developed, which can not only work in contact mode, but also can work indynamic mode including first-order, second-order and even higher-order resonant states.The dissertation mainly introduces the following parts that have been finished.(1) The characteristics of the higher-order resonant cantilever in dynamic mode AFMare analyzed, including the derivation of vibration equation and vibration mode functionof the cantilever, and verification that the dynamic characteristics of the higher-orderresonant cantilever are significantly improved compared with the basic resonant mode.(2) The circuit design of the multi-mode AFM system, including the amplitudefeedback and phase feedback circuit. The circuits in contact feedback mode include thecontact mode, the first-order resonant mode and the second-order resonant mode.(3) The improvements of AFM mechanical structures, including the measuring headand the working platform. After improvements, the system becomes more stable, andthe scanning range in X and Y directions is4times larger than before, so does the axialadjustable distance is6times larger.(4) The performance test of the multi-mode AFM, including the noise test, theapproach curve test, the3D topography test and so on in both static and dynamic modesunder amplitude feedback control, as well as the comparison of sensitivity, resolution,and time response between the first and second order resonant cantilever. Besides, thenoise, approach curve, and3D topography under phase feedback control are also tested.(5)The factors that influence the accuracy of the multi-mode AFM are analysed, andsome possible optimization methods are proposed.The scanning measurement in each mode is realized based on the home-builtmulti-mode AFM. The feasibility of scanning measurement using the higher-orderresonant cantilever is verified through experiments. Moreover, it is theoretically andexperimentally proved that the higher-order resonant cantilever has higher sensitivity,higher resolution, and faster scanning speed.