| The study of the properties of a single-molecule or single-atom,such as the electrical,optical,and magnetic properties of the molecule or atom,is an important and urgent work for the current micro-world scientific research.Mechanical Controllable Break Junction(MCBJ)and Scanning Tunneling Microscopy-Break Junction(STM-BJ)technique are widely used as the main technical means for the study of single molecule and elemental electronics.Because the single-molecule and single-atom are only a few nanometers in size,the measurement process under this scale is very vulnerable to the external environment.The most significant disturbance is the vibration from the environment.The slight vibration of the external environment makes it impossible for the single-molecule to be stably connected between the electrode pair.Therefore,most of the single-molecule measurement instruments need to be designed with high-performance vibration isolation devices to reduce the external vibration interference and improve the accuracy of precision instrument measurement.For most of the precision measurement of single-molecules,the core measurement components are very sensitive to external vibration,and the price is also very expensive.Therefore,it is difficult to directly test and optimize the performance of the vibration isolation system by means of experimental methods.For this reason,this paper proposes a new method for the vibration isolation design based on mathematical modeling and simulation.Firstly,the simulation model is used to study the performance of the vibration isolation system.Then,parameters of the vibration isolation system are optimized based on the simulation,resulting in the final design to be verified by the experiment.This design method can not only shorten the design of the vibration isolation system,but also reduce the design cost.This paper mainly focuses on the design and optimization of vibration isolation system for Mechanical Controllable Break Junction(MCBJ)instruments.By using numerical modeling and simulation techniques,an applicable method for quickly designing high-performance vibration isolation systems is proposed.It is not only avoiding a large number of experimental tests,and obtaining good results,but also giving a new way of the vibration isolation system design for precision instrument.The main works and results of the thesis are concluded as follows:(1)For the MCBJ characterization platform,a simple and applicable vibration isolation device was designed.According to the structure of the device,a relevant mathematical model of vibration transmission was established.(2)By using COMSOL MULTIPHYSICS software,the mathematical model was numerically simulated and the vibration process was simulated.Based on this,the vibration isolation performance of the vibration isolation device was investigated,and three important parameters for determining the vibration isolation performance of the vibration isolation device were found:the elastic coefficient of the elastic element in the vibration isolation system,the mass of the suspension and the geometry of the testing platform.(3)Through the analysis to the model and the simulation results,the general rules for improving the performance of the vibration isolation system have been discovered,and the optimal structure of the platform with the best vibration isolation performance has been found,that provide a guideline for the vibration isolation system design.(4)According to the simulation results,three actual vibration isolation devices with different parameters were designed.Based on the experimental data from the MCBJ test,the performances of the three devices were analyzed and compared demonstrating the feasibility and effectiveness of the vibration isolation system design method proposed. |
PDF Full Text Request