Formation of surface oxides and Ag2O thin films with atomic oxygen on Ag(111)

- Ag(111) exposed to gas-phase oxygen atoms in UHV.
- Oxygen atoms formed over a hot Ir filament at either 1750 K or 2000 K.
- Chemical state of adsorbed oxygen depends on filament temperature.
- Ag2O thin film forms with higher dissociation temperature.
- Surface oxides and subsurface oxygen form at lower filament temperature.

The nature of the oxygen species adsorbed to silver surfaces is a key component of the heterogeneously catalyzed epoxidation of ethylene and partial oxidation of methanol over silver catalysts. We report the formation of two different silver-oxygen species depending on the flux and energy of incident gas-phase oxygen atoms on an Ag(111) surface. A combination of surface science techniques was used to characterize the oxidized surfaces. Atomic oxygen was generated with an Ir filament; lower temperatures created surface oxides previously reported. When O was deposited with a higher filament temperature, the surface became highly corrugated, little subsurface oxygen was observed, and thin layers of Ag2O were likely formed. These results show that the energy and flux of oxygen are important parameters in the chemical identity and abundance of oxygen on silver surfaces and suggest that formation of the Ag2O thin film hinders formation of subsurface oxygen.

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