Heteroepitaxial subsurface growth mode resulting in interlayer mixing

A subsurface growth mode which results in interlayer mixing has been revealed from an interplay between scanning tunneling microscopy and ab initio total-energy calculations for the growth of Pd on Cu(110) and Ag(110) surfaces. On Cu(110), the Pd initially alloys into the surface layer forming ordered linear -Pd-Cu- chains. As the coverage is increased, the -Pd-Cu- chains remain at the same level, but become covered, partly by Cu atoms expelled during alloying, partly by substrate material supplied from steps and terraces. This results in a very rough surface morphology, even at relatively low Pd coverages. Similar structures were observed on Ag(110). The observed growth mode is expected to apply to other heteroepitaxial systems as well.