Development Of High-resolution AFM And Its Application To Mechanics And Small Molecular Structure

With the emergence of surface analytical instrument - Scanning Tunneling Microscope (STM) and Atomic Force Microscope (AFM) in 1980s, nanotechnology has developed rapidly in the past 20 years. STM and AFM are widely used in many fields for their atomic-level resolution, especially in material science, biology, nano-mechanics and small molecule structure. With the development of nanotechnology, STM and AFM, as the most important tools in nano-measuring and nano-machining, are playing an increasing important role in the nano-observing and micro-machining fields. The size of small molecule structure is about 0.5 nm, and it is very difficult to use commercial AFM to observe the space morphology of small molecule structure because its lateral and vertical resolutions are 0.2 nm and 0.05 nm respectively. The work described in this paper was funded by the"985 Project"key subject and a special Foundation of College. The development of high-resolution AFM.IPC-208B and its application were researched. The major innovative achievements described in this paper are as follows:①The lens body design of high-resolution AFM.IPC-208B and its realization were given. This lens body consists of stepping motor, piezoelectric ceramics, cantilever, variable speed system and workbench. In this lens body, the combined structure of mechanical transmission and piezoelectric ceramics were designed to realize the transmission, orientation and scanning in large scope, yet its accuracy is on the nano-scale. On the basis of thoroughly analyzing the generation mechanism of noise and vibration, some improved measures had been taken to reduce noise and vibration, and these measures included the use of the damped vibration workbench, the suspended spring and the synthetic rubber buffer. In AFM.IPC-208B, there are thirteen degrees of freedom of this workbench devised to enhance its resolution and enlarge its scope of measuring and processing, among which six degrees of freedom are offered by the upper and lower piezoelectric ceramics, four degrees of freedom are used for the motion of workbench along X, Y, Z1, and Z2 direction, and the rest forming the 3-D polar coordinates system (r,θ, z ) are applied to the adjustment of cantilever. In AFM.IPC-208B, STM can be used alone.②Some new theories of data acquisition and scanning control system were given. In its preamplifier, the single-amplifier circuit was replaced with the three-stage linear amplification circuits, which could decompose magnification times and reduce Signal-to-Noise. The broken-line amplifier was replaced with the logarithm amplifier SH325 to ensure the linear feedback of control loop. The fourteen bits D/A card and the external clock were used to avoid the generation of noise signal when computer executes other instructions and to break up the limitation of 1 ms precision from computer's internal clock, in D/A card the upside-down T resistance network was installed.③The application of AFM.IPC-208B to roughness measurement was discussed. The special programs of 2-D and 3-D roughness parameters calculation were programmed based on MATLAB language, and the surface morphology of DLC film were observed by AFM.IPC-208B and from the obtained data the 2-D and 3-D roughness parameters were calculated and analyzed by the special programs. From these results the following conclusions can be drawn: AFM.IPC-208B can measure the nano-scale roughness of DLC film surface and its 3-D roughness parameters are more stable and more reliable than its 2-D ones.④The application of AFM.IPC-208B to micro-fabrication was studied. Based on STM performance of AFM.IPC-208B, the micrometer-scale line was etched on HOPG surface by mechanical etching method, and its width and depth were about 5μm and 30μm, respectively.⑤The small molecule structure morphology of WO3 sol film adulterated with platinum, ZnO and TiN film and the micro-morphology of gene chip surface were observed by AFM.IPC-208B, and their corresponding structural parameters were also obtained. The above results have never been seen in home and abroad reports and possess higher scientific values.