Wachstum amorpher Schichten: Vergleich von Experiment und Simulation im Bereich Oberflächenrauhigkeit und mechanische Spannungen

Abstract

Structure formation and mechanical stresses of amorphous and polycrystal films, prepared by evaporation, sputtering and PLD, are investigated, and modelled with the help of Monte-Carlo simulations, molecular dynamics simulations and continuum growth models.The growth of amorphous vapor deposited films is characterized by a pronounced structure formation and intrinsic mechanical stresses in dependence of the film thickness, independent of the details of the alloy. In contrast, films prepared by sputtering and PLD are much smoother. After substrate dependent early stages of growth, film growth in the medium film thickness regime (typ. 100nm) can be characterized by rather smooth growth. In the late stages of growth, the films roughen significantly. By a systematic experimental variation of the preparation parameters, it is possible to identify the major atomic mechanisms of mesoscopic structure formation and intrinic film stresses, and to correlate both aspects. In the framework of continuum growth models, which include surface diffusion, self shadowing and hill coalescence as major atomic mechanisms, a quantitative understandig of structure and tensile stresses in the high film thickness regime is possible. A surface reconstruction mechanism can explain the measured compressive stresses. It is also possible to study relaxation mechanisms in this framework.By a combination of experiments, numerical analysis and modelling with discrete and continuum models, it is possible to identify dominant mechanism on the atomic scale concerning their mesoscopic and macroscopic effects in experiment and theory and to compare with each other.