Strain dependence of adatom binding energies and diffusion barriers in homo- and heteroepitaxies of $\mathrm{Si}$ and $\mathrm{Ge}$ on $\left(001\right)$ surface has been studied using first-principles calculations. In general, $\mathrm{Si}$ adatom binding energies and diffusion barriers are larger on $\mathrm{Si}\left(001\right)$ and $\mathrm{Ge}\left(001\right)$ surfaces than a $\mathrm{Ge}$ adatom, in accordance with decreasing bond strength from $\mathrm{Si}\text{−}\mathrm{Si}$ to $\mathrm{Si}\text{−}\mathrm{Ge}$ and to a $\mathrm{Ge}\text{−}\mathrm{Ge}$ bond. The overall surface diffusion anisotropy of $\mathrm{Si}$ and $\mathrm{Ge}$ adatoms is found to be comparable on both $\mathrm{Si}\left(001\right)$ and $\mathrm{Ge}\left(001\right)$. The essentially linear dependence of binding energies and diffusion barriers on external strain is reproduced in all the cases, giving strong evidence for a priori quantitative prediction of the effect of external strain on adatom binding and surface diffusion.

• Received 2 February 2004

DOI:https://doi.org/10.1103/PhysRevB.70.155320