Migration of an Al adatom on the clean, H-terminated, or partly H-terminated diamond (001) surfaces

Abstract

The migration mechanism of Al atoms on diamond (001) surfaces has been investigated by theoretical calculations with the molecular-orbital method using the semiempirical approximation and/or the first-principles method using the density-functional theory. Computations were performed on three kinds of different surfaces: (1) a $2\ifmmode\times\else\texttimes\fi{}1$ reconstructed clean surface, (2) a H-terminated $2\ifmmode\times\else\texttimes\fi{}1$ monohydride surface, and (3) a partly H-terminated surface. The lowest potential-energy paths for the Al adatom migration were determined for the above three diamond surfaces. The activation energy required for the Al diffusion on the clean surface was estimated to be 0.7 eV, whereas the energy required for the diffusion on the H-terminated surface was very small $(\ensuremath{\sim}1 \mathrm{meV}).$ Further, the transfer of an Al adatom from the H-terminated to the nonterminated regions occurred spontaneously with a large energetic stabilization over 3 eV. It is strongly suggested from these theoretical results that the fabrication of thermally stable regulated Al nanostructures is possible on diamond (001) surfaces using the H termination as a mask for selective metal growth.