Investigation Of Low Energy Pt Atoms Impacts On Pt(111) By Molecular Dynamics Simulation

The understanding of the thin film growth mechanism is a primary task in the thin film research field. The study on micro-mechanism of the thin film growth at atomic level will reveal the physical nature of thin film, and will be of great significance in both the development of equipments of thin film manufacture and the invention of new thin film materials. Energetic particle deposition is one kind of thin film synthesis technique based on energetic beam, such as, IBAD, PLD, IBD etc, which is considered to be of good prospect for wide range of applications. However, comprehensive and systematic understanding has been hardly achieved about the growth mechanism of energetic deposition, especially low energetic deposition. In this thesis, the low energy depositions of incident Pt atom on Pt(111) surfaces doped with Cu, Ag, Au, Ni and Pd were simulated by molecular dynamic method (MD) and embedded atom method (EAM). The influence of low energetic deposition on the growth model of thin film in the earlier stage of growth was discussed. In addition, we expand the doped system to six kinds of noble metals' interaction and principles as well as atomistic mechanism of the influence of substitutional impurities on the stability of the system surface was analyzed.The major points of this work were summarized as followings:A. Interaction between low energetic atoms and substrate surface.During the interaction of low energetic Pt on Pt(111)surface, a sputtering threshold exists, ranging from 30 to 40eV. It is found that adatom yields, vacancy yields and sputtering yields will all increase along with the energy of incident atoms getting higher. Meanwhile, the quantities as well as distribution of adatom and vacancy play an important role in film growth. If we increase the energy of incident atoms reasonably, which will enlarge adatom yields, vacancy yields and their distribution area, layer by layer growth model will be advanced .B. Influence of substitutional impurities on the stability of noble metals' (111) surface.Surface impurities in noble metals' (111) surface will change the surface energy of the system because of the difference of cohesive energy and the difference of atomic radius between the impurities and the substrate atom. If the cohesive energy of the impurities is higher than that of the substrate ones or the doped atoms are bigger than the substrate ones, surface energy will be larger. On the contrary, the surface energy will be lower. We can forecast the segregation of binary alloy by the change of surface energy. It is also found that for noble metals' (111) surface the impact of substitutional impurities on surface vacancy formation energy depends on the impurities' cohesive energy, atomic radius and alloy heats of solution.C. Interaction between low energetic atom and doped substrate surface.The main effect of the introduction of substitutional impurities to noble metal Pt(111) surface, suchas Cu, Ag, Au, Ni, Pd, etc., is to decrease the surface energyi.e., increase the stability of the system. Compared with the results on pure Pt(111) surface, adatomyields, sputtering yields and vacancy yields are a little lower obtained from the interaction of low energetic Pt and doped Pt(111) surface. Substitutional impurities have changed the local density distribution of adatom and vacancy, which will somewhat influence nucleation and further change the growth model and the atomistic state of the film.