The movement of ion pairs on the surfaces of simple oxides was examined. Using temperature-accelerated dynamics, the elementary processes involved were identified and the activation energies for these were used as inputs to kinetic Monte Carlo simulations. Results were presented for the motion of BaO and SrO ion pairs on the (100) surfaces of BaO and SrO, respectively, and the formation of island pairs on these surfaces was studied. The simulations revealed the importance of exchange mechanisms in surface diffusion and the growth of oxides. The importance of such reactions was little recognized in ionic systems, where it was assumed that ionic surface diffusion occurred via the hopping motion of ion pairs from one surface site to another. Exchange mechanisms could dominate transport processes on both terraces and steps, for both homo-epitaxial and hetero-epitaxial growth. It was suggested that unavoidable mixing, which occurred when an exchange mechanism operated, had to be considered when attempting to grow sharp interfaces in oxide nanostructures.

Simulating Surface Diffusion and Surface Growth in Ceramics. M.Y.Lavrentiev, D.J.Harris, J.H.Harding, N.L.Allan, J.A.Purton: Dalton Transactions, 2004, 19, 3071-5