Atomistic investigation of diffusion processes at Al(Si)/Si(111) interphase boundaries obtained by simulated vapor deposition

Abstract

Molecular dynamics and parallel-replica dynamics simulations are applied to investigate the atomic structures and diffusion processes at $\text{Al}\left\{111\right\}\parallel \text{Si}\left\{111\right\}$ interphase boundaries constructed by simulated vapor deposition of Al(Si) alloy on Si(111) substrates. Different orientation relationships and interface structures are obtained for different pre-deposition Si (111) surface reconstructions. Diffusion of both Al and Si atoms at the interfaces is calculated and compared with diffusion along grain boundaries, triple junctions, contact lines, and threading dislocations in the Al–Si system. It is found that $\text{Al}\left\{111\right\}\parallel \text{Si}\left\{111\right\}$ interphase boundaries exhibit the lowest diffusivity among these structures and are closest to the lattice diffusivity. In most cases (except for the Si substrate), Si atoms are more mobile than Al atoms. The diffusion processes are typically mediated by Al vacancies and Si interstitial atoms migrating by either direct or indirect interstitial mechanisms.