Molecular Dynamics Simulation Of Mechanical Properties And Defect Movement Of Semiconductor Material Si

The design and prediction of the crystal structures and properties of materials aided by computers can be achieved through numerical simulation. It is the main researchful direction of the current material field. There have been extensive applications in many fields for the semiconductor material Si due to its excellent mechanical properties, easy growing the large and high-purity crystal etc. But, there are still many unresolved problems in the aspects of microstructures, mechanical properties and defect movement due to limitations in research method. The mechanical properties and defect movement of Si has been investigated by molecular dynamics simulation (MD) and the code GULP in this work and it is helpful for further understanding of the microstructure of Si.Firstly, the present status and research progress of the semiconductor material Si the importance of computer in material design and the development of computer simulation for Si is systematically reviewed. Molecular dynamics simulation and Interatomic potential of Si are also elucidated. Furthermore, the code GULP and the module of calculation used in this article are simply introduced.Secondly, the cohesive energy and mechanical properties of Si are calculated using different potentials and different parameters of potential, then the parameters of potential is optimized. The analysis indicates that for diamond-cubic Si, using the Stillinger-Weber (SW) potential could obtain more stable structure (the minimum cohesive energy) and show better change of properties than using the Terrsoff potential. And, the cohesive energy, lattice constant and bulk modulus are also calculated by using the modified SW parameters. The new result is more reasonable and comes to be highly consistent with the experimental values.Thirdly, through the simulation of the vacancy movement along the crystallography orientations of <111> and <110>, the result of analysis shows that the energy barrier of vacancy movement is the smallest when the vacancy moves along the <111> crystallography orientation, the vacancy mainly moves along the <111> crystallography orientation in Si crystal. Moreover, the energy barrier (about 4.1eV) calculated by using the modified SW parameters is consistent with the published value (the range from 4.0eV to 5.0eV).Finally, the issue of confirming the suitable parameters of MD is introduced. We obtain the most suitable parameters by analysis: the time step size is 0.001ps; Leapfrog Verlet is chosen as the integration method; the system size is 4×4×4; the equilibrium step is 4000; Then, the melting point of Si is calculated based on these parameters, and the value of the melting point by simulation is agreement with the experimental values.