| Invented by Dr. Gerd Binnig and Heinrich Rohrer,the scanning tunneling microscope (STM) is the first device that gains the real space image of atoms. Ever since then,great varieties of Scanning Probe Microscopes (SPM) were developed on the base of STM. Now in the field of nano-technology,the STM has been an indispensable tool for observation and research. It has also been widely used in various fields such as physics,chemistry,material science,bioscience,microelectronics,opto-electronics and so on. Therefore,the research about STM not only has significations in theoretics,but also has wide applications.STM has many intrinsic excellences such as its high resolution reaching nanometer level even atom level,its function of gaining real space images of sample surface,its ability to manipulate atoms and so on. On the other hand,most of STMs were produced overseas. These STMs are always equipped with advanced components such as vacuum chamber,therefore they are costly and require severe maintenance. Meanwhile,they have complex parameters to be set in the human-computer interfaces,which are all in English. These disadvantages limit the popularization and application of STM in China. The aim of this thesis is to develop a high-powered,applied and simple STM,which will help the scanning tunneling microscopy expediently and effectively used in various scientific areas.The research content and achievements of this thesis are as follows.It provided a in-depth discussion about the mechanism of tunneling effect as well as the I-V relation and the expression of tunneling current based on the model of metal-insulator-metal.We have constructed a detecting device of STM for open environment,realized the isolation of environmental vibrations and the shield of electrical noises. On this base,we also designed the CCD monitor system,which is used to real-timely detect the approach of the tip and the sample. This system also realized a freewill choose of scanning-area in specifically scope.We have designed the scanning and control system,which includes a pre-amplifier,a PID feedback and scanning-control circuit,high-voltage amplifiers and so on. The function of controlling scan and feedback has been realized.We have optimized the software of data acquisition and computer control,and integrated some functions in the program,such as scanning parameters setting,real-time display of scanning images and some essential image processing and three-dimensional display.Using this STM,many samples were scanned to test its capability. The atom graphics and nano- structure graphics of Highly Oriented Pyrolytic Graphite (HOPG) were gained as well as some other samples. Stable scan has been observed during all of the experiments,it has been concluded that the system works well in open environment.Some capability parameters of this STM system are as follow:the lateral resolution: 0.1nmthe vertical resolution: 0.01nmthe scanning range: 2 nm X 2 nm - 2000 nm X 2000 nmthe max scanning velocity:1 frame/2sthe size of image: 180X180 pixels or 400 X 400 pixelsthe image format: BMP filethe image processing: image cropping,image smoothing,addingfalse color,three-dimensional display..On this base,the cost of this system has been controlled on a low level. The operation of this system is easy to learn therefore the system doesn't need person specially assigned for maintenance. The anticipation of this thesis has been realized. |
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