Study On Energetic Deposition And Heteroepitaxial Behavior By Moleculer Dynamics Simulation

Low-temperature plasma assisted film growth is one of important method to improve film properties and has been applied in the fabrication of films. The study on the mechanism of film growth at atomic level will reveal the great significance in controlling growth conditions, optimizing the characters of thin films manufacture and developing novel film materials. From the viewpoint of atomic level, the film growth is a non-equilibrium surface dynamical process, including deposition, diffusion, nucleation of atoms, as well as growth. In this thesis, low-energy depositions, surface diffusion of adatoms and evolution of heteroepitaxial islands were simulated by molecular dynamic method (MD) with embedded atom method (EAM).We investigated the yields and distribution of adatoms, sputtering atoms and vacancy induced by the interaction of low energetic Pt incident atoms and Pt(111) surfaces. It is found that there is a sputtering threshold, ranging from 30 to 40eV. With increasing the energy of incident atoms, yields of adatoms will be enlarged and the distribution area will be expanded. In addition, the existence of substituted impurities will change the stability of the surface and affect the yields of adatoms. In the study of low energetic sputtering of Pt(111) surfaces, it is found that the sputtering yield induced by light incident atoms is higher than that of heavy atoms, which does not agree with the linear cascade theory based on the binary collision model. A new physical mechanism for low energy sputtering, where the reflection of incident atom by target atom dominates the sputtering process of surface atoms, is suggested.For the study on diffusing processes of adatoms, interaction between the adatoms and the substrate, interaction between two adatoms and its influence on surface diffusion are presented, in the sight of lattice deformation caused by the adatoms. The results show that, the Cu adatom may have an impact on the substrate as deep as 10 layers and will lead to ununiformity of the distribution of surface strain and local pressure. In the process of adatom diffusion, the deformation induced by the interaction of adatom and substrate plays an important role in the adatom's migration. Additionally, an adatom can exert impact on the diffusion of another adatom in certain distance by a direct interaction between the two adatoms and an indirect interaction caused by lattice deformation strain field of the substrate.In the research of heteroepitaxial growth, it is concluded that the dominant reasons of heteroepitaxial behavior should be attributed to bonding properties, including bond length, bond angle and bond energy but not the traditional lattice mismatch theory. Essentially...