Floating stacking fault during homoepitaxial growth of Ag(111)

We have investigated the influence of Sb on the formation of stacking faults during Ag(111) growth using x-ray scattering. In equilibrium, a predeposition of 1/3 monolayer Sb results in a (root 3 X root 3)R 30 degrees reconstruction in which the top layer is wrongly stacked. Upon continued Ag growth at 100 degrees C, the Sb segregates and the Ag atoms return to the correct stacking, while the new Ag atoms in the top layer again have the wrong stacking. This thus effectively leads to a floating stacking fault. Because of kinetic limitations, the same effect occurs for lower Sb coverages.