Study On Scanning Control System Of Atomic Force Microscopy Stage

Based on analyzing and summarizing the development of the atomic force microscope (AFM), the principle and work modes of AFM are discussed. The problems existing in the measurement of AFM are pressented. Such impacts as figure of the cantilever with the tip, interference to the system and hysteresis of piezoelectric stage on the result of the measurement are analyzed. Some correlative parts of the probe are designed.The piezoelectric stage is one of the most important parts of AFM, however its hysteresis characteristic severely influences the position precision and scanning precision of the AFM system. With the research on the hysteresis phenomena of the AFM piezoelectric stage, a mathematical model is derived, which can describe any curve of the hysteresis. The simulation and experiment results demonstrate that the mathematical model can precisely describe hysteresis phenomenon, and the error between the simulated and the measured is only about 1%, which provides theory foundation for the control method of AFM piezoelectric stage.A scanning system under open loop operation based on the mathematical model is studied and designed, including the identification of hysteresis model parameters and obtaining of the inverse model. Experiments are desinged to prove the precision of the system. The experimental results demonstrate that the position precision is improved apparently, and the positional error of the system reduces from 10% to 1.5%.To improve the precision of the piezoelectric stage further, a scanning close loop system based on the mathematical model is studied and designed. Experiments are also desinged to prove the precision of the close loop system. The experimental results demonstrate that the positional error of the system reduces to 0.1%, and the close loop system has high dynamic performance and position precision.The scanning control system of AFM piezoelectric stage studied in this paper improves the satge's scanning precision, position precision, the reliability of AFM system.