Study On Heteroepitaxial Growth Of Au/Cu,Ag/Cu And Cu/Au System By Molecular Dynamics Dynamics Simulation

Heteroepitaxial growth is an important subject in film growth. The study on film growth at atomic level is helpful to reveal the nature and physical mechanism of film growth. Moreover, these studies are useful to improve the technology and the film quality. In this thesis, the heteroepitaxial growths for Au/Cu(001), Au/Cu(111), Ag/Cu(001), Ag/Cu(111), Cu/Au(001) and Cu/Au(111) were simulated by molecular dynamic method(MD) with embedded atom method(EAM). The morphological evolution, local pressure map, adhesion energy and deformation energy were studied.The major points of this work were summarized as follows:1. In the process of heteroepitaxial growth, morphology of heteroepitaxial island is correlated to the environment nearby. In heteroepitaxial growth on (001) surface, at the relative positions of the atoms at bridge sites are higher than the positions of the atoms at four-fold hollows. In the case of (111) surface, however, the atoms at bridge sites are lower. The difference between (001) and (111) results from competition between the interactions of the atoms in the islands and the interactions of the atoms of the islands to substrates. In some processes of epitaxial growth, typical morphologies have been observed: Ag-c(10×2) structures formed in Ag/Cu(100) growth; Moire structures were found on Ag/Cu(111) surfaces; self-assemble phenomena of epitaxial island appeared in the growth of Cu/Au(111).2. From analysis of local pressure, we found that atoms on the bridge sites are in the state of strong tension. Atoms in Moire" structure in the growth of Ag/Cu(111) are in the state of strong tension, too. However, in the growth of Cu/Au(111), self-assemble of atoms in the islands increases the interactions of the atoms, and decreases the bonding between the island and the substrate.3. Adhesion energy of Au-Cu is larger than that of Ag-Cu and bonding between island and substrate of (001) surface is larger than that on (111) surface. The order of adhesion energy of epitaxial growths, from large one to small one, are Cu/Au(001), Au/Cu(001), Au/Cu(111), Ag/Cu(001), Cu/Au(111), Ag/Cu(111). Deformation energy of Cu/Au(001) and Cu/Au(111) growth is the largest, which suggests that in these two growth processes, epitaxial island has significant influence on substrate. Following them areAg/Cu(001) and Ag/Cu(111) system. The deformation energy in Au/Cu(001) is the smallest. In all of the simulations, deformation energy on (001) surfaces is always smaller than that on (111) surfaces, which tells us that islands on (111) surfaces has stronger effect on substrate, i.e., instability of epitaxial growth on (111) increases.