By studying the growth of Cu2O islands during the initial oxidation stages of (001)Cu, using  in situ  transmission electron microscopy, it was found that the predominant mechanism for the growth of 3-dimensional islands was the surface diffusion of O. There was also a non-negligible contribution, to metal oxide growth, which arose from another mechanism. This was suggested to be the direct impingement of O atoms on the oxide islands.

J.C.Yang, M.Yeadon, B.Kolasa, J.M.Gibson: Applied Physics Letters, 1997, 70[26],