A PdO(101) thin film grown on Pd(111) in ultrahigh vacuum

We present experimental results demonstrating that a high quality PdO(101) thin film can be grown on Pd(111) in ultrahigh vacuum by oxidizing the metal at 500 K using an oxygen atom beam, followed by annealing to 675 K. Low energy electron diffraction (LEED) images show that the [010] direction of the PcO(101) thin film aligns with the [-110] direction of the Pd(111) substrate, and that the PdO film grows in three degenerate domains, rotated 120 degrees relative to one another. Based on excellent agreement between the experimental and simulated LEED patterns, we conclude that the surface structure of the PdO thin film deviates minimally from bulk-terminated PdO(101). Recent temperature programmed desorption (TPD) experiments also provide evidence that the PdO(101) thin film on Pd(111) is terminated by the stoichiometric surface in which half of the Pd atoms are coordinatively unsaturated (cus), corresponding to a cus-Pd atom density equal to about 35% of the surface density of Pd(111). The ability to generate a well-defined PdO(101) surface in ultrahigh vacuum should provide new opportunities for conducting model surface science studies of PdO, particularly studies aimed at elucidating the reactivity of PcO(101) toward species important in commercial applications of Pd catalysis. (C) 2008 Elsevier B.V. All rights reserved.