Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5426738 | Surface Science | 2006 | 15 Pages |
The interaction of O2 with Pd single crystals including Pd(1Â 1Â 1), Pd(1Â 1Â 0) and Pd(1Â 0Â 0) in the pressure range 1-150Â Torr was studied using scanning tunneling microscopy (STM). The Pd single crystal surface morphologies were determined by the oxidation conditions: O2 pressure, exposure time and treatment temperature. Oxygen dissolution into Pd metal followed by the formation of bulk oxide was observed. The dissolution of oxygen resulted in the increase of the inter-planar spacing between the first two layers, 9-14% increase after an exposure of Pd(1Â 1Â 1) to 10-25Â Torr O2 at 600Â K for 10Â min, and 10-20% increase after exposing Pd(1Â 1Â 0) and Pd(1Â 0Â 0) to 1Â Torr O2 at 600Â K for 10Â min. Elongated or semi-spherical oxide agglomerates along the steps nucleated and grew on both Pd(1Â 1Â 0) and Pd(1Â 0Â 0) surfaces after oxidation in 5-25Â Torr O2 at 600Â K. When bulk PdO was formed, the single crystal surface was covered with semi-spherical agglomerates 2-4Â nm in size, which tended to aggregate to form a “cauliflower-like” structure. The single crystal surface area also increased during oxidation.