Basic Theory And Research Of The Key Technology Of STM In Wide Scope And Higher Speed

Scanning tunneling microscope (STM), one of the most effective and important means of testing and processing in manometer technology, is receiving ever-increasing popularity in its application with the coming of nanometer technology. Beside the stabilization of the instrument itself, the quality of its pictures, the simplicity of its operation, the expansion of its application sphere and the trend of it becoming an industry have aroused more and more concerns.On the basis of analyzing the current situation of STM's research and application nationally and internationally, the paper makes thorough theoretical analysis into the defects of STM made in China. Thorough experiment and research the success of STMIPC-205B has been seen, which expands STM's application sphere and lays good foundation for the popularization of STM in China,The main research contents of the thesis are shown as follow: the basic design theory of scanning and controlling system, e.g. the design theory and accomplished route of pre-amplifier and logarithm amplifier, which satisfy the request of STM scanning with high precision, low noise and good linearity in wide scope and higher speed; the design theory and accomplished route of lens body according with requests above; the physical mechanism and improved steps concerning noise and vibration which influence the theoretical precision of STM.The important and developed achievements are shown as follow:(1) The new design theory of scanning and controlling system has been put forward, which satisfy the request of STM scanning in wide scope and higher speed. The tunnel-current is weak signal(nA), the relationship between tunnel-current and tunnel-distance is exponential, the feedback pressure which accord with requests of controlling precision(mV) and linearity arrives at decades volts. In the past, owing to single-amplifier and broken-line amplifier, we can obtained more satisfying images if STM scans in narrow scope and lower speed. We have broken up enlarged multiples and reduce noise proportion of signal by replacing the single-amplifier with tri-degree linear amplifier, as well as, adopt logarithm amplifier to insure linearity of feedback volt. The new design theory makes it possible that STM scans in wide scope and higher speed.(2) Using the combination of reformed mechanical structure and piezoelectricityceramic, we fulfill driving, going to and examining of needle in nm level and wide scope. The limit coming from dynamic scope of piezoelectricity ceramic has been broken through by designing high-precision tri-dimensional digital display work platform, the scanning scope has been broadened from 20 y mX 20 u m to 25mm X 25mm,the reliability of process in nm level is improved also.(3) For the aim that STM is not influenced by surroundings , on the basis of analyzing reasons results in noise and vibration, some improved steps has been adopt to reduce vibration and noise as well as using method of wavelet to deal with images. The steps include: In order to restrain noise when computer performs other orders, exterior-clock is adopt to break through limit from computer's interior-clock; using main board and perfect screened body of lens, reducing long wire connections, separating the step-motor-controlling machine with the data-gathering-system machine, using vibration-reducing of holographic platform to absorb energy having high frequency or low frequency, improving rigidity of STM to abstain resonance, using the intelligent and digitalized control model, high-precision A/D(D/A) cards to increase the precision.The research of this thesis possesses important academic meanings and practicality, on the basis of breaking through basic theory and designed theory concerning with STM, we make use of the fruit of research of integrated circuit, computer, mechanical engineering and other correlated technology. It has established base for expanding applied scopes of STM made in China.