Epitaxial growth of RuO2(100) on Ru(10(1)over-bar0): Surface structure andother properties

We determined the surface structure of RuO2(100) formed on Ru(1010) by empl oying the techniques of low-energy electron diffraction (LEED) and density functional theory (DFT) calculations. The RuO2(100) film grows lattice-matc hed with its [010] direction along the [0001] direction of Ru(1010) (4.5% c ompressively strained), while it grows incommensurately with the [001] dire ction of RuO2(100) along the [1.210] direction of Ru(1010). The RuO2(100) s urface is terminated by bridging O atoms, which are attached to the coordin atively unsaturated Ru (cus-Ru) atoms with a bond length pf 2.01 Angstrom. The other Ru-O bond lengths are in the range of 1.90-2.05 Angstrom, typical for bulk RuO2. Due to the presence of cus-Ru atoms on RuO2(100), CO molecu les adsorb quite strongly as evidenced by a desorption state at 300-400 K. The activity of the RuO2(100) surface for the CO oxidation reaction is simi lar to that of RuO2(110). The surface energies of RuO2(110) and RuO2(100) a re 71 and 87 meV/Angstrom (2), respectively.