Dependence of strain energy on the grain orientations in an FCC-polycrystalline film on rigid substrate

Abstract

A thin polycrystalline film attached to a bulk substrate of different thermal expansion coefficient will experience a thermal strain when the temperature is changed. Calculations of the strain energies for various grain orientations relative to the film surface were made for an FCC polycrystalline film on a substrate. Results show that prior to yielding, the four lowest strain energy densities correspond to grains with (1 0 0), (5 1 1), (3 1 0) and (3 1 1) planes oriented parallel to the plane of the film. In a yielded film, the four lowest strain energy densities correspond to the grains with (1 1 0), (1 0 0), (5 1 1) and (2 1 1) planes oriented parallel to the plane of the film. From strain energy minimization, grains with (1 0 0), (5 1 1), (3 1 0) and (3 1 1) or (1 1 0), (1 0 0), (5 1 1) and (2 1 1) planes oriented parallel to the plane of the film should be favorable in an attached FCC-polycrystalline film after annealing, depending on the degree of deformation of the film.