CU ADSORPTION ON CO FILMS - EDGE DECORATION VERSUS INTERMIXING

Heteroepitaxial growth of the Co-Cu system is investigated by scanning tunneling microscopy. Cu deposited on Co/Cu(001) decorates the step e dges of Co islands and forms nanometer-sized rings. Subsequent deposit ion of Co transforms the film morphology from compact to heterogeneous ly intermixed. We relate this growth asymmetry to the largely differen t surface free energies of Co and Cu, which impose a diffusion barrier at Co-Cu boundaries, and to atomic exchange processes that occur in t he presence of Co adatom gas. (C) 1997 Elsevier Science B.V.