Intermixing and two-dimensional alloy formation in the Na/Au(111) system

The adsorption of Na on Au(111) has been studied by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Upon thermal activation ordered structures are formed which consist of intermixed Na-Au layers. A thermodynamically stable hexagonal NaAu2 layer with a lattice constant of ~ 5.4 Å is identified, which can be regarded as a two-dimensional alloy.