Molecular Dynamics Simulations of Structural Relaxation of Two-dimensional Lattice Mismatch Epitaxial Aluminum Thin Film
|Course||Materials Physics and Chemistry|
|Keywords||dislocation two-dimensional lattice mismatch thin film aluminum molecular dynamics simulation|
The epitaxial growth under the condition of two-dimensional lattice mismatch is relatively close to the actual film growth. Knowing its essential nature of epitaxial film growth from the atomic aspect has some leading significance in theory in improving the thin film preparation process and the quality of film. This thesis applies the three-dimensional molecular dynamics simulations, using the fourth-order Predict-Correct algorithm to solve systematic equation of motion, using the Embedded Atomic Method Many-body potential to calculate the interaction among aluminum atomics, using Langevin constant temperature algorithm to maintain the constant temperature. It offers respective simulation study of structural relaxation of the two-dimensional lattice mismatch epitaxial aluminum thin film of atomic layers with the temperatures of 300K,500K,700K and 800K, of the film thickness of 1,3,6,10,15, with the condition of its mismatch at±2%,±4%, and±6%. The main conclusion is as follows:1. The thickness of misfit dislocations appeared is related with the temperature and the mismatching degree:when the mismatch is the same, with the relatively high temperature, misfit dislocation appears slightly thinner than that with low temperature; When temperature is the same, with the mismatching degree increasing, the mismatch dislocation thickness becomes gradually thinner.2. The mismatch character has great influence on the structure of the two-dimensional lattice mismatch epitaxial aluminum thin film and the dislocation formation:With the same conditions, the epitaxial thickness needed in the formation of negative dislocation is thinner than that of the positive mismatch degree, or the dislocation formation happens earlier when the thicknesses is the same; With the negative mismatch situation, the dislocation formation begins from a squeezing atomic group in triangle cone-shape in a surface layer. While the dislocated formation begins in distorted pit area in the atomic surface layer with the positive mismatch situation; when the structure is stable, the negative mismatch system squeezes out the partial atomic layer in surface; the pit will appear in the four quarters of positive mismatch system.