AVS 63rd International Symposium & Exhibition
    Surface Science Monday Sessions
       Session SS+AS+HC-MoM

Paper SS+AS+HC-MoM6
D2O Interaction with Planar ZnO(0001) Bilayer Supported on Au(111): Structures, Energetics and Influence of Hydroxyls

Monday, November 7, 2016, 10:00 am, Room 104E

Session: Mechanistic Insights on Surface Reactions in Catalysis and at Novel Interfaces
Presenter: Xingyi Deng, National Energy Technology Laboratory
Authors: X. Deng, National Energy Technology Laboratory
D.C. Sorescu, National Energy Technology Laboratory
J. Lee, National Energy Technology Laboratory
Correspondent: Click to Email
Ultrathin oxides with single or few atomic layers are considered new types of due to the emergence of film-specific structures with properties distinct from their bulk counterparts. ZnO(0001) bilayer grown on Au(111) adopts a planar, graphite-like structure via an intralayer relaxation from the bulk wurtzite structure. In this work, we investigate the interaction between D2O and the planar ZnO(0001) bilayer grown on Au(111) with temperature programed desorption (TPD), low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. D2O molecules adsorbed on this planar surface form two ordered overlayers, a (3 × 3) and a (√3 × √3)R30°, not seen before on any of the bulk ZnO single crystal surfaces. The apparent activation energies of desorption (Ed) estimated from TPD peaks agree well with the adsorption energy values calculated from DFT. The DFT calculations also reveal that both overlayers are mediated by extensive hydrogen bonding among the molecules but with different packing densities. The hydroxyl groups, accumulating very slowly on the ZnO(0001) bilayer surface under the standard ultrahigh vacuum (UHV) environment, strongly suppress the formation of the (√3 × √3)R30° overlayer but have less impact on the (3 × 3) overlayer. We suggest that the difference in packing densities of the overlayers leads to these findings such that only the (3 × 3) overlayer with a more open structure can accommodate small amounts of the adsorbed hydroxyls.