K and mixed K+O adlayers on Rh(110)

The evolution of the structure of the adlayers and the substrate during adsorption of K and coadsorption of K and O on Rh(110) is studied by scanning tunneling microscopy and low-energy electron diffraction. The K adsorption at temperature above 450 K leads to consecutive (1 x 4), (1 x 3), and (1 x 2) missing-row reconstructions for coverage up to 0.12 ML, which revert back to (1 x 3) and (1 x 4) with increasing coverage up to 0.21 ML. The coadsorption of different oxygen amount at T > 450 K and eventually following reduction-reoxidation cycles led to a wealth of coadsorbate structures, all involving substrate missing-row-type reconstructions, some including segmentation of Rh rows along the [110] direction. The presence of K stabilizes the (1 x 2) missing-row reconstruction, which facilitates the formation of a great variety of very open (10 x 2)-type reconstructions at high oxygen coverage, not observed in the single adsorbate systems.