| Nano-science and technology is a foreland and cross subject that developed around 1990. It has developed many branches, such as nano-microelectronics, nano-phase materials science, nano-mechanics, nano-biology, nano-physics, nano-particles chemistry and so on. In the new century, nano-technology will play an important role in the development of science and technology.In the field of nano-technology, SPM is the basement and has become an indispensable tool for observation and research. There are great varieties of scanning probe microscopes (SPMs). Among them, atomic force microscope (AFM) has been most widely applied in various fields such as material science, microelectronics, bio-medical science, optics, physics, chemistry and so on. In some special occasions, however, test samples should be placed in liquid. For example, many chemical reactions and electrochemical reactions react in liquid; organic samples such as protein are active only in liquid; materials that are very easily oxidized cannot be exposed in air. Therefore, the research about AFM measuring in liquid has not only the important theoretical significations, but also the wide applications. The aim of this thesis is to develop a powerful and practical AFM measuring in liquid, which will extend the applied field and help the atomic force microscopy expediently and effectively used in various scientific areas.The research content and innovation of this thesis are as follows.It provides detailed discussion about the mechanism of the acting force between the sample and the probe tip. We have calculated the buoyancy acting on the tip in liquid and the interfacial force acting on the tip when it enters into liquid.We have developed a novel method of AFM measuring in liquid, the probe tip of which is totally put into the liquid during scanning. In most of the previous version of AFM measuring in liquid, a liquid-drop is simply dropped on the sample surface, and the AFM tip is only capable of scanning the surface in the liquid-drop. Firstly, the sample is not totally submerged. Secondly, the probe tip and the optical beam path areundoubtedly disturbed by the interfacial force. While in our new design, these problems can be successfully avoided. We have designed a transparent window, it makes the beam path get across the interface of air-solid and solid-liquid, rather than the air-liquid path. So the beam path of the AFM measuring in liquid is not disturbed by the surface fluctuation of the liquid. Furthermore, the probe tip is not influenced by the interfacial force, because the interfacial force only act on the transparent window, not on the probe.We have developed a new version of AFM measuring in liquid at the first time. Besides the merit we have discussed above, it has more strongpoint. The microprobe scans in XYZ directions; the sample holder and liquid cell are designed for open environment. So almost there is not any weight and dimension restriction on the sample, i.e., bigger and heavier samples can also be measured by the AFM measuring in liquid. Furthermore, it can carry out in-situ and online scanning on sample surfaces. With these significant characteristics of the system, we can make real-time research on some chemical reaction such as iron corrosion. Thus, the AFM measuring in liquid is much more practical and will be widely applied.We have compiled the software of data acquisition and system control, and have integrated some functions in the program, such as scanning parameters setting, real-time display of images, and some essential functions of image processing. We have put real-time control and data acquisition into effect.Using this AFM measuring in liquid, many experiments and research have been carried out. Some samples were scanned to test its capability. The nano-structure images of aluminum as well as some other samples were obtained. Furthermore, the procedure of corrosion on sample surface in acid has been successfully observed using this system. These experiments show that the AFM system works well in bot... |
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