Nature and dynamics of the OPd(110) surface bonding

Abstract

The nature and dynamics of the OPd(110) surface bonding is analyzed by incorporating a compact model of bond-to-band and the potential-barrier into the outcomes of LEED, STM, XPS, UPS, angular-resolved photoemission spectroscopy (ARPS) and the thermal desorption spectroscopy (TDS). A model of buckleddipole and a description of the bonding dynamics are suggested. To form a Pd 2O tetrahedron, the precursor O −1 in a Pd 5O cluster evolves into a threefold-coordinated O −2. The hybridized-O −2 bonds to one Pd atom underneath and one Pd in the surface, and the O −2 polarizes its two surface neighbors through nonbonding lone pairs. The buckled metal dipoles yield zigzag protrusions in the STM images. It is shown that the outstanding spectral features are recognized as the binding processes and modified density-of-state. For example, the ARPS features around −2.0 and −4.5 eV below E f are identified as the Osp 3 nonbond and bond states, respectively. The work-function-change derived from the UPS relates to the antibonding dipole subband. The characteristic features in the exposure-resolved TDS correlate to individual processes of ionic OPd bond, nonbonding lone pair, and the virtual bond formation. Hence, it is essentially realistic to interpret the reaction as the dynamics of the O −1 developing into the hybridized-O −2.