Effects of surface diffusional anisotropy on the current-driven surface morphological response of stressed solids

A comprehensive analysis is presented of the effects of surface diffusional anisotropy on the morphological stability of planar surfaces of stressed crystalline solids under the simultaneous action of an electric field. The analysis is based on self-consistent dynamical simulations of driven surface morphological evolution in conjunction with linear stability theory. Results are reported of a systematic study of the effects on the surface morphological response of varying surface diffusional anisotropy parameters; these include the direction of the applied electric field with respect to fast surface diffusion directions, the surface crystallographic orientation, and the strength of the anisotropy that increases with decreasing temperature. For face-centered cubic crystalline solids under stress, we find that there exists a preferred direction for the applied electric field that optimizes their surface morphological response. In addition, we find that for these solids under given surface electromigration conditions, the morphological response of their ⟨ 111 ⟩ -oriented surfaces is superior to that of their ⟨ 100 ⟩ -oriented and ⟨ 110 ⟩ -oriented surfaces. Furthermore, we demonstrate that increasing the strength of the surface diffusional anisotropy in these materials has beneficial effects on their surface morphological stability under the simultaneous action of an electric field. Our predictions can provide guidance for experimental studies of surface morphological response to the combined action of electric fields and mechanical stresses, as well as for tailoring operating conditions to improve the mechanical reliability of thin films in service.