Combined STM, LEED and DFT study of Ag(100) exposed to oxygen at near atmospheric pressures

I. Costina1, M. Schmid2, H. Schiechl2, M. Gajdoš3, A. Stierle1, S. Kumaragurubaran1*, J. Hafner3, H. Dosch1, P. Varga2

1Max-Planck Institut für Metallforschung, 70569 Stuttgart, Germany
2Institut für Allgemeine Physik, Technische Universität Wien, 1040 Wien, Austria
3Institut für Materialphysik and Center for Computational Materials Science, Universität Wien, 1090 Wien, Austria
*present address: National Institute for Material Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Japan

Surf. Sci. 600 (2006) 617-624

We have investigated the interaction of molecular oxygen with the Ag(100) surface in a temperature range from 130 K to 470 K and an oxygen partial pressure ranging up to 10 mbar by scanning tunnelling 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 O2, the individual oxygen atoms are randomly distributed on the surface. When the sample is exposed to 10 mbar O2 at room temperature, small p(2x2) reconstructed patches are formed on the surface. After oxidation at approx. 470 K and 10 mbar O2 pressure the surface undergoes a c(4x6) reconstruction coexisting with a (6x6) superstructure. By ab-initio thermodynamic calculations it is shown that the c(4x6) reconstruction is an oxygen adsorption induced superstructure which is thermodynamically stable for an intermediate range of oxygen chemical potential.

Corresponding author: A. Stierle. Reprints also available from M. Schmid (schmid< encoded email address >).

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