Design Of A Laser Force Measuring System For AFM Nanotweezer

In order to better understand the nano-world and thereby promote applications of the nanotechnology in fields of material, biology, medicine, information, etc., the research of nanotechnology and the development of the nano-fabrication equipments have became a focus of technological competition among countries. AFM (Atomic Force Microscopy) is one of the most important tools used in the nanotechnology. By detecting interaction forces between the AFM tip and the nano-world, AFM can be used for the nanoscale imaging of surface morphology, nano-material properties characterization, and accurate control of nano-manipulation. This thesis is suppoted by the National Natural Science Foundation of China through the project"the basic research on multi-scale manipulation and connction of three-dimensional nano-structures and devices", aiming to develop a laser force-measuring system for a home-built dual-probe AFM nanotweezer, and complete its accurate calibration.For the force detection during the three-dimensional operation and control, a laser force measuring system, based on the principle of optical deflection method, was designed for the AFM nanotweezer. Interferences among system components and laser paths are fully considered and the designed system has high detection precision, compact structure and favorable operability. Moreover the AFM nanotweezer laser force measuring experimental system was established.In addition, a new calibration device was developed for sensitivity calibration of the AFM laser force measuring system. Both the normal and lateral sensitivity of the laser force measuring system can be obtained with this calibration device. A nonlinear calibration method has been used to compensate the nonlinearity of PSD (photoelectric position detector), so as to effectively broaden the linear range of the force measurement, thereby providing precise force detection and control in the three-dimensional manipulation through the AFM nanotweezer. Finally, a series of experiments were completed by using the laser force-measurement system, such as sample surface morphology scanning, probe-substrate pull-off force and friction measurement. Experimental results show that the force-measurement system can provides accurate forces description between tip and objects in the process of nanomanipulation, and be capable of very high force detection with a precision of dozens of pico-Newton.The research of AFM nanotweezer laser force-measurement system promote the development of precisely controllable three-dimensional nanomanipulation and nanoassembly methods, and has certain practical value for the study of nano technology.