Molecular Dynamics Study Of The Microstructure And Properties Of Ti/Al Deposition Thin Film

The preparation and properties analysis of nano-scale metallic multilayers havebeen the subject of intense study in recent years. In particular, the Ti-Al alloy thin filmsare attractive for a broad range of applications to aircraft and industry due to their highstrength, high melting temperature, desirable oxidation and creep resistances, combinedwith low density. To achieve well defined optical, electronic and magnetic properties, itis necessary that the films be flat on an atomic scale and that interdiffusion does notoccer. The film preparation techniques include physical vapor deposition, chemicalvapor deposition and molecular assembly. Owing to the limitations of experiment,Molecular Dynamics method on the scale of atom is adopted to imitate the film growthprocess through physical vapor deposition, to obtain the optimum deposition parameters.It can provide theoretical support for the experiment and prediction.In this thesis, we investigate the film growth process of Ti/Al (001) under variousdeposition process parameters. We focus on the roughness、 intermixing andmicrostructure of the deposition films. The main contents in this thesis are listed asfollows:Firstly, the effects of different incident angle on films are investigated. TheRoot-mean-square roughness, packing density, radial distribution function and thepercentage of pair bonds of Ti thin film have been calculated. The results indicate thatthe effects of incident angle on surface roughness and packing density are small whenthe incident angle is less than30°; but when the incident angle is more than30°,thesurface roughness increases and the packing density decreases, especially when theincident angle is60°, the Ti film obeys the fibrous growth mode. Increasing theincident angle has minor effects on the microstructure of Ti thin film, growing with anfcc structure.Secondly, the effects of different incident energy and substrate temperature onfilms are studied and compared. The results of simulation show that the surfaceroughness of the grown film could be reduced when the incident energy and/orsubstrate temperature increase. Two kinetic factors, local acceleration and theincorporation energy barrier, are introduced to analyze the interface intermixing. Because the energy barrier is two or three times higher than other transition metals, theintermixing amount is interface-confined, instead of compounds. Furthermore, themicrostructure of Ti thin film is studied by radial distribution function (RDF) and pairanalysis technique (PA). It is demonstrated that increasing the substrate temperature hasremarkable effect on the structural configuration of the deposited Ti films, while theincident energy dependency is negligible. When the substrate temperature is300K andbelow, Ti thin film grows mainly with an fcc structure. As the temperature is increased,the components of fcc structure decreases, whereas the component of the disorderedstructure increases.In general, the thesis has systematically studied the Ti/Al(001) thin films accordingto adatom incident angle, incident energy and substrate temperature, to provided atheoretical basis for the film growth.