Structural transformations on an oxidized $\mathrm{Ag(111)}$ surface

The structure of the $\mathrm{Ag(111)}$ surface after the adsorption of molecular oxygen at a temperature of $300$ K is studied by low-temperature scanning tunneling microscopy. It is established that local surface oxide is formed at the first stage of adsorption. The subsequent adsorption of $\mathrm{O}_2$ results in the appearance of new objects with a size of $3$–$8$ Å and a height of $1.0$–$1.5$ Å on the $\mathrm{Ag(111)}$ surface, which form quasi-ordered structures with increasing degree of coating. The heating of the system obtained up to $500$ K leads to a structural transition resulting in the formation of single islands of the $p(4\times4)$ phase on the surface. Surface structures are identified by a simulation based on the density functional theory.