Stranski-Krastanov like oxide growth on Ag(1Â 1Â 1) at atmospheric oxygen pressures

The oxidation behavior of Ag(1 1 1) was studied by means of in situ surface X-ray diffraction at atmospheric oxygen pressure. Exposure to 1 bar oxygen at 773 K reveals a competing growth of three different oxygen-induced structures on Ag(1 1 1), namely the well-known p(4 × 4) reconstruction, a surface oxide in a p(7 × 7) coincidence structure and the bulk oxide Ag2O in (1¯1¯1¯) orientation. The latter two exhibit the same honeycomb on hexagon arrangement of the Ag sublattice with respect to the Ag(1 1 1) surface. An inverted stacking of Ag planes in the bulk oxide islands is observed as compared to the Ag(1 1 1) substrate, which sheds new light on the Ag2O formation process. Finally, we present a structural model of the p(7 × 7) reconstruction, based on a three-layer O-Ag-O slab of Ag2O(1 1 1).