Diffusion of a self-interstitial atom in an ultrathin fcc film bonded to a rigid substrate

Abstract

AbstractThe determination of the interstitial sites and saddle points corresponding to the diffusion of an interstitial atom in ultrathin face-centered cubic (fcc) film is of particular interest. The outcome is strongly influenced not only by the orientation of the free surface but also by the location of the defect with respect to the free surface and film-rigid substrate interface. In this article, an atomic-scale simulation is conducted to analyze the effects of depth on the out-of-plane interstitial mechanism of diffusion. To ensure reasonable accuracy and numerical convergence, the atomic interaction up to the second-nearest neighbor is considered. The ab initio examination of the above-mentioned problem associated with thin films requires a large supercell and is computationally time consuming. However, for the sake of demonstration, the values of the barrier height energy pertinent to a diffusing self-interstitial atom in the bulk material are computed using both the first principles density functional theory (DFT) and the developed technique, indicating reasonable correspondence.