Ge/Ag(111): Surface alloy of a semiconductor on a metal

We present one of the first experimental studies of the formation of an ord ered surface alloy of a semiconductor, Ge, and a metal, Ag, with bulk tende ncy to phase separation. The kinetics of growth at room temperature as well as the surface segregation of Ge have been investigated for the (111) orie ntation using Auger Electron Spectroscopy (AES) and Low Electron Energy Dif fraction (LEED). The growth mode of Ge on Ag(111) is layer-by-layer like up to at least two layers. An unexpected ordered surface alloy forming a p(root 3 x root 3)R30 degrees superstructure is observed during the growth at 1/3 germanium mono layer, followed by a p(7 x 7) superstructure at one-monolayer coverage. The surface Ge segregation studied via both dissolution and segregation kineti cs shows the particular stability of the ordered p(root 3 x root 3)R30 degr ees surface alloy.