Studium superstuktur NO na povrchu Pd(111) pomocí LEED.

A LEED study of NO superstructures on the Pd(111) surface

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We have examined two adsorption structures of NO on the Pd(111) surface and the transformation between them. Low-energy electron diffraction (LEED) I (V ) curves of the Pd(111)-p(2 x 2)-NO and Pd(111)-c(4 x 2)-NO surface structures were acquired and analyzed using tensor LEED. Our structural models confirm a previous study by scanning tunneling microscopy and DFT (Hansen et al 2002 Surf. Sci. 496 1). In the c(4 x 2)-NO structure, which forms at an NO coverage of 0.5 monolayers (ML), the NO molecules occupy fcc and hcp hollow sites and are almost upright with only slight tilting, possibly related to NO-NO repulsion. In the p(2 x 2)-NO structure (0.75 ML), with two NO molecules in hollow sites and one in an on-top site, we find strong tilting of the on-top molecule. Upon heating, thermal desorption of NO leads to a transition from the p(2 x 2) to the c(4 x 2) structure, which leads to splitting of the diffraction spots and/or streaky spots. The transition is discussed in terms of domain walls.

Byly analyzovány dvě struktury NO na povrchu Pd(111): Pd(111)-p(2 x 2)-NO a Pd(111)-c(4 x 2)-NO a jejich vzájemný přechod pomocí metody tensor LEED.

We have examined two adsorption structures of NO on the Pd(111) surface and the transformation between them. Low-energy electron diffraction (LEED) I (V ) curves of the Pd(111)-p(2 x 2)-NO and Pd(111)-c(4 x 2)-NO surface structures were acquired and analyzed using tensor LEED. Our structural models confirm a previous study by scanning tunneling microscopy and DFT (Hansen et al 2002 Surf. Sci. 496 1). In the c(4 x 2)-NO structure, which forms at an NO coverage of 0.5 monolayers (ML), the NO molecules occupy fcc and hcp hollow sites and are almost upright with only slight tilting, possibly related to NO-NO repulsion. In the p(2 x 2)-NO structure (0.75 ML), with two NO molecules in hollow sites and one in an on-top site, we find strong tilting of the on-top molecule. Upon heating, thermal desorption of NO leads to a transition from the p(2 x 2) to the c(4 x 2) structure, which leads to splitting of the diffraction spots and/or streaky spots. The transition is discussed in terms of domain walls.

NO, PD(111), tensor LEED, superstruktura

NO, PD(111), tensor LEED, superstructure

2009

16.03.2009

0953-8984

Journal of Physics: Condensed Matter

21

13

134005-1–134005-7

7