Combined STM, LEED and DFT study of Ag(1 0 0) exposed to oxygen near atmospheric pressures

Abstract

We have investigated the interaction of molecular oxygen with the Ag(1 0 0) surface in a temperature range from 130 K to 470 K and an oxygen partial pressure ranging up to 10 mbar by scanning tunneling microscopy, low electron energy diffraction, Auger electron spectroscopy and ab initio density functional calculations. We find that at 130 K, following oxygen exposures of 6000 Langmuirs O 2, the individual oxygen atoms are randomly distributed on the surface. When the sample is exposed to 10 mbar O 2 at room temperature, small, p(2 × 2) reconstructed patches are formed on the surface. After oxidation at ≈470 K and 10 mbar O 2 pressure the surface undergoes a c(4 × 6) reconstruction coexisting with a (6 × 6) superstructure. By ab initio thermodynamic calculations it is shown that the c(4 × 6) reconstruction is an oxygen adsorption induced superstructure which is thermodynamically stable for an intermediate range of oxygen chemical potential.