Structural and electronic properties of Pt modified Au(100) surface.

Investigations on electronic and geometric structures of platinum adsorbed on monocrystalline gold surfaces are important for understanding the remarkable catalytic properties of bimetallic Pt-Au systems. Herein, the morphology of quasi-hexagonal (hex) Au(100) surface after deposition of platinum for coverage up to 0.5 monolayer (ML) has been investigated by scanning tunneling microscopy (STM). For coverage range 0.2-0.4 ML the creation of elongated islands with mono-atomic height is observed. The islands consist of flat phase of disordered Pt-Au alloy which coexists with nanowire-like features with a hex atom arrangement and quantized width. Annealing the Pt/Au(100) system at 100-150 °C changes the surface morphology. The islands disappear and the topmost layer of the surface consists of flat phase of Pt-Au alloy which coexists with the hex-stripes. Small domains of ordered c(2 × 2) structure of Pt-Au alloy are found. The electronic properties of this structure have been investigated by ab-initio calculations. The obtained results allow to distinguish the Pt from Au atoms by their appearance in the STM images. The calculated electronic structures indicate a bonding creation between Pt and Au atoms and an electron d-states redistribution of Pt in comparison to the bare Pt(100)-(1 × 1) surface.