Texture Maps for Orientation Evolution During Grain Growth in Thin Films

Abstract

Orientation selective grain growth in thin films arises due to anisotropy in materials properties. For continuous thin films, there are at least two orientation dependent driving forces for grain growth: (i) surface and interface energy anisotropy; (ii) strain energy anisotropy (both elastic and plastic). In fcc metals, the preferred growth of grains with (111) texture occurs due to their low surface and interface energy. Stresses in thin films arise during deposition and as a result of post-deposition annealing. A texture dependence of strain energy density arises in biaxially strained thin films due to anisotropy of elastic properties and/or orientation-dependent yield stresses. For most fcc metals, the strain energy driving force promotes the growth of (001) grains due to minimization of the combined elastic and plastic strain energy. The magnitudes of the orientation dependent driving forces for grain growth depend on the characteristics and processing conditions of the film and substrate. We have performed grain growth experiments for Ag films on single crystal Ni on MgO; Ag films on plasma-enhanced chemical vapor deposited (PECVD) SiO₂ on MgO; Ag films on oxidized Si; and Ni films on oxidized Si. The texture resulting from grain growth in films of different thicknesses and deposited at different temperatures were determined, and the results are presented in the form of texture maps. The texture which dominates as a result of grain growth can be understood through the use of texture maps and compares well with analytic models for texture development during grain growth in thin films.