Microstructure and morphology evolution during the growth of faceted thin films.

The research presented in this dissertation addresses development of a microstructure scale model to study the deposition of faceted thin films. The model is based upon the principle of evolutionary selection due to competitive growth of differently oriented facets and grains. We investigate a wide range of growth scenarios, from the chemical vapor deposition of diamond, to the optimization of microstructure by manipulation of growth conditions, to the oblique deposition of films grown physical vapor deposition conditions. The present simulations are all two-dimensional continuum models. The simulation algorithm tracks the growth surface and crystal orientations during film growth. From this data, we extract the temporal evolution of the crystallographic texture, microstructure (grains, voids, etc.) and morphology of polycrystalline faceted thin films. We have analyzed the evolution of such average parameters as the mean grain size, grain size distribution, surface roughness, crystallographic texture and growth zones as a function of a series of parameters that represent atomic scale growth properties, Quantitative comparisons between the predicted structures and experiments show that this model reproduces the central microstructural features of films grown under a restricted class of conditions (where surface diffusion is negligible). The main application of the present model examined in this dissertation is the chemical vapor deposition of diamond. In order to be able to control the structural properties of thin films, the central goal is to establish the relationship between growth conditions and microstructure. We investigate two modes of optimizing film structure. In the first, we examine how changing the relative velocities of crystal facets by manipulating the gas composition during chemical vapor deposition can be used to grow films with the required bulk structure and morphology. The second mode is through the control of the deposition angle during physical vapor deposition. The orientation of grain columns, the porosity, the crystallographic texture, and grain size are shown to be sensitive to the deposition angle. In order to isolate the effects of shadowing from other physical effects (such as surface diffusion, deposition species size, flux divergence, etc.), we have constructed a simulation where all of these effects are completely removed.Ph.D.Applied SciencesChemical engineeringMaterials scienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126211/2/3016931.pd