HETEROEPITAXIAL SUBSURFACE GROWTH MODE RESULTING IN INTERLAYER MIXING

A subsurface growth mode which results in interlayer mixing has been r evealed 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 incre ased, the -Pd-Cu- chains remain at the same level, but become covered, partly by Cu atoms expelled during alloying, partly by substrate mate rial supplied from steps and terraces. This results in a very rough su rface morphology, even at relatively low Pd coverages. Similar structu res were observed on Ag(110). The observed growth mode is expected to apply to other heteroepitaxial systems as well.