Tem Study of Yielding in Polycrystalline Gold Thin Films

We have used transmission electron microscopy (TEM) to study the microstructure of thin gold films which were grown on 〈100〉 rock salt. The samples were annealed on the rock salt substrate or on a gold TEM specimen grid. Films annealed on rock salt had a larger mean grain size than those annealed on TEM grids. All of the annealed films have a 〈111〉 preferred orientation. Several cracks are observed in the film annealed on rock salt. Plastic yielding of the film was identified by the presence of dislocations, and is caused by tensile stress derived from grain growth. In spite of the uniform texture of the films, the observed dislocations were concentrated only in some individual grains, while their surrounding grains remained dislocation-free. Yielded grains showed no difference of orientation that would lead to higher Schmid factors, so other predictors of yielding must be considered.