Ordered surface alloy formation of immiscible metals:: The case of Pb deposited on Ag(111) -: art. no. 155424

The deposition of 1/3 Pb monolayer at room temperature onto Ag(111) leads to a (root 3x root 3)R30 degrees superstructure. We present here a detailed structural study of this surface structure by synchrotron radiation surface x ray diffraction (SR-SXRD) and scanning tunnel microscopy (STM). We show that Pb atoms are embedded into the silver top surface layer forming an ordered Ag2Pb surface alloy despite the strong tendency of the system to phase separate in the bulk. Quenched molecular dynamics simulations allow us to interpret this ordering reversal, in terms of size-mismatch induced surface alloying.