Theoretical And Experimental Research On Thermophysical Properties Of Nano Thin Films

Thin films with thickness in microscale and nanoscale are important subassemblies in the application areas such as integrated-circuit transinstors, quantum-well lasers and microelectromechanical systems. Since the performance and reliability of the devices are strongly dependent on the heat conduction in thin films, exploring thin film thermal conductivity is of great significance for the design of these devices.This paper elucidates the process of the material micromation, the theory of thermoelectricity cooling, and the recent research of micro-scale thermal transport; discusses the basic theory, detailed steps of molecular dynamics simulation, the classification and application conditions. Based on linear response theories, the thermal properties of solid argon are simulated by equilibrium molecular dynamics method. It is found that thermal expansion may reduce thermal conductivity over the temperature range of 20–80 K, while the variational trend of thermal conductivity relative to temperature is close to the experimental data. After comparing with the thermal conductivity under two different conditions, the thermal conductivity with vacancy is lower than that with Kr, which accounts for phonon scattering on impurities due to lattice strain is stronger than that due to differences in mass between the defect and the surrounding matrix. Simultaneously the results of simulation and experiment can be fitted with a function . In the second part of the thesis, the thermal properties of superlattices is simulated by non-equilibrium molecular dynamics method. It is found that the thermal conductivity and the proportion of interface thermal resistance in total thermal resistance do not change with the number of periods for the superlattice structure with a fixed period length. However, when the total length of the thin film is fixed, the thermal conductivity will increase with the period length and the interface distortion can be observed due to the lattice mismatch. Simultaneously the average interface thermal resistance will go up with period length. Finally, the paper discusses the theory and experimental process of method. Some interesting experimental data are obtained through measuring the thermal conductivity of SiO2 films.