GROWTH ANISOTROPY AND SELF-SHADOWING - A MODEL FOR THE DEVELOPMENT OFINPLANE TEXTURE DURING POLYCRYSTALLINE THIN-FILM GROWTH

The development of a preferred crystallographic orientation in the pla ne of growth, an in-plane texture, is addressed in a model that incorp orates anisotropic growth rates of a material and self-shadowing. Most crystalline materials exhibit fast growth along certain crystallograp hic directions and slow growth along others. This crystallographic gro wth anisotropy, which may be due to differences in surface free energy and surface diffusion, leads to the evolution of specific grain shape s in a material. In addition, self-shadowing due to an obliquely incid ent deposition flux leads to a variation in in-plane grain growth rate s, where the ''fast'' growth direction is normal to the plane defined by the substrate normal and the incident flux direction. This geometri c growth anisotropy leads to the formation of elongated grains in the plane of growth. Neither growth anisotropy alone can explain the devel opment of an in-plane texture during polycrystalline thin-film growth. However, whenever both are present (i.e., oblique incidence depositio n of anisotropic materials), an in-plane texture will develop. Grains that have ''fast'' crystallographic growth directions aligned with the ''fast'' geometric growth direction overgrow grains that do not exhib it this alignment. Furthermore, the rate of texturing increases with t he degree of each anisotropy. This model was used to simulate in-plane texturing during thin-film deposition. The simulation results are in excellent quantitative agreement with recent experimental results conc erning the development of in-plane texture in sputter deposited Mo fil ms. (C) 1997 American Institute of Physics.