Multiscale approach to material synthesis by gas phase deposition

Abstract
Structure and morphology of materials obtained from CVD varies. It can be a submicron film or a multimicron layer of amorphous, polycrystalline or single crystal material on a substrate (epitaxial films). The comprehension of the main features characterizing the growth of these materials is complicated by chemical and physical events occurring at length scales differing for even some orders of magnitudes. For example the fluid phase behavior can be studied through continuous conservation laws, which satisfactorily describe temperature profiles, streamlines and local chemical composition at the length scale of the reactor. In contrast, elementary reactions occurring in the gas phase or on the deposition surface take place at the atomic scale, since they involve the interaction between molecules or between molecules and surface atoms. Finally, if the investigated aspect is the collective surface behavior, then models that can span from the nanometer to the micron scale must be introduced. Here, different models that can be adopted to study phenomena occurring at different length scales are described. One of the principal goals of this work is to link the reactor operating conditions with film properties such as deposition rate, chemical composition, impurity level, and hardness.