Strain energy anisotropy in germanium and other diamond-cubic polycrystalline films

Based on elastic theory strain energy densities of grains with various textures have been calculated in diamond-cubic polycrystalline films. The results show that the strain energy density is anisotropic. The (100) grains have the lowest strain energy density, while the (111) texture corresponds to the highest one. It is the reverse for surface energy density. Therefore, strain energy minimization and surface energy minimization favor different crystalline orientations of grain growth and compete to determine the final texture of thin films. Discussion turns out that such competition in germanium films, as in other diamond-cubic films, results in a (100) texture barely appearing because the strain energy anisotropy can not dominate during grain growths.