Grain Growth and Texture Evolution in Thin Films

Microstructural and texture evolution during grain growth in polycrystalline thin films was investigated. Grain growth in thin films is a coarsening process driven by the reduction of grain boundary energy, surface energies, and strain energy density. Because crystal properties can be anisotropic, grain growth in thin films is an orientation selective process. Surface and interfacial energy minimization or reduction favors the growth of grains with low combined surface and interfacial free energy. For the films and substrates investigated in this thesis, surface and interfacial energy promotes the growth of (111)-textured grains. Thin films on thick substrates are usually subjected to a non-zero state of strain, arising from differential thermal expansion between the film and the substrate, from densification and from intrinsic strains. For elastically deformed fcc metal films, strain energy density promotes the growth of (001)-textured grains. In plastically deformed films, strain energy density can favor the growth of (011)-textured grains; this results from the orientation dependence of the yield stress of grains in thin films. (111) grains are predicted to maximize the yield stress, and (011) grains are predicted to have low yield stress. An analytic model for texture evolution during grain growth in thin films can be developed by equating the magnitudes of the orientation-dependent driving forces, for pairs of orientations. The