Germanium adsorption on Ag(111): An AES-LEED and STM study

: The adsorption of germanium on Ag(111) has been investigated using Scanning Tunneling Microscopy, Auger Electron Spectroscopy and Low Energy Electron Diffraction. From the shape of the Auger peak-to-peak versus time curves, we deduce that at room temperature the growth mode is nearly layer-by-layer at least for the first two layers. In the sub-monolayer range, the growth starts by the formation of a (mean square root of 3 x mean square root of 3)R30 degrees surface superstructure which is complete at 1/3 monolayer coverage. Beyond this coverage a rectangular c(mean square root of 3 x 7) superstructure is observed. STM images reveal that this last reconstruction is formed by an ordered arrangement of self-assembled Ge tetramers giving rise to a surprising undulation of the surface.