Molecular Dynamics And Lattice Dynamics Simulation Of Thermal Expansion Property Of Si Single-Crystal

Silicon is the most widely used semiconductor material which has the most abundant storage on Earth, and it has a large number of applications in the field of microelectronics. The last twenty years, the silicon material in micro-electromechanical systems are also widely used,as people successfully developed a variety of silicon micro-pressure sensors, silicon microscale accelerometers. Thermal properties is a fundamental physical properties of silicon material, for their understanding and knowledge will help us to successfully design and reliable use of micro-electromechanical systems based on various components of silicon materials. For the silicon single-crystal materials,Thermal expansion is the most important type of thermal properties,which has long been the object of sufficient theoretical and experimental research. Through many experiments,people found that it has a negative thermal expansion phenomenon at low temperature, studies have shown that, with Stillinger-Weber model, people can not be calculated to get negative thermal expansion coefficient at low temperatures. Therefore,this model can not explain the physical mechanism of negative thermal expansion of silicon single-crystal materials at low temperatures, and must be corrected.This paper will reveal the microscopic mechanism of silicon crystals with negative thermal expansion properties at low temperatures, it willalso amend Stillinger-Weber model, so that it can be applied to study the thermal expansion of silicon single-crystals. And it can provide a theoretical basis for the rational design of MEMS components and its reliable use. The research method is also applicable to the thermal expansion properties of other crystalline materials of diamond structure,which is universal.The main contents of this paper include:1. Introduction The thermal properties of silicon material, especially the theoretical and experimental study of the current situation and significance of thermal expansion properties.2. Introduction the basic principles of molecular dynamics simulations of monocrystalline silicon under Stillinger-Weber model and the main steps and processes of molecular dynamics simulation, and simulation with the experimental data.3. Using the lattice dynamics method to derive the relationship between the thermal expansion coefficients of silicon single-crystal and third-order force constants in two-body and three-body interaction of silicon atoms, Through the use of perturbation theory to derive lattice constants and thermal expansion coefficients formulas of silicon single crystal, so as to explore the physical properties of silicon single-crystal which has a negative thermal expansion at low temperatures.4. Comparing lattice dynamics simulation results, moleculardynamics simulation results and experimental data of silicon single-crystal thermal expansion properties, and drawing the relevant conclusions: silicon single-crystal do exist negative thermal expansion property at low temperature, positive third-order force constant is the basic cause of this property.