STM investigation of surface alloy formation and thin film growth by Sb4 deposition on Au(1 1 1)

The growth of thin antimony films on the Au(1 1 1) surface at room temperature is studied by scanning tunneling microscopy (STM) in ultrahigh vacuum. At coverages up to one monolayer nanometer-sized islands are formed on the Au(1 1 1) terraces. High resolution STM images of these islands allow the distinction of gold and antimony atoms and confirm the formation of a well-ordered surface alloy. Its symmetry and interatomic distances agree well with the unreconstructed (1 0 0) plane of the bulk compound AuSb2. With increasing antimony coverage amorphous layers grow on the alloy support. In the initial stage of the amorphous layer growth ordered regions with cubic lattice structure are found in the overall amorphous films. The measured lattice constants and symmetries of these local structures imply that they consist of undissociated Sb4 clusters.