Effect of grain orientation in x-ray diffraction pattern on residual stress in polycrystalline ferroelectric thin film

The grain orientation is represented by orientation distribution function through the volume fraction in case of discrete oriented grains, and we propose an orientation average method to evaluate residual stress in polycrystalline ferroelectric thin film from mesomechanics to continuum mechanics. In order to verify the method's validity, x-ray diffraction patterns of the previous polycrystalline ferroelectric thin films with random orientation and preferred orientation are chosen as samples to evaluate surface residual stresses, and they are compared with the residual stresses evaluated by the conventional and extended sin(2) psi methods. Furthermore, the origin of the total residual stress is theoretically discussed from epitaxial stress, intrinsic stress, thermal stress, and phase transition stress, in order to verify the reliability of the orientation average method. It is only appropriate for thin film with random orientation via the specific diffraction peak however appropriate for thin film with not only random orientation but also preferred orientation via all the diffraction peaks. It is very necessary to consider grain orientation for evaluating residual stress in polycrystalline ferroelectric thin film. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748052]