A LOW-ENERGY-ELECTRON DIFFRACTION STUDY OF OXYGEN, WATER AND ICE ADSORPTION ON PT(111)

We present low-energy electron diffraction (LEED) studies of a p(2 x 2 ) overlayer of oxygen, a monolayer of water and a multilayer ice film on Pt(111). Oxygen adsorbs in a fcc hollow site; buckling in the first two substrate layers leads to a local expansion of the substrate unde rneath the oxygen. Water adsorbs as a disordered monolayer and diffuse LEED intensities (DLEED) can be observed. From the structure of the d iffuse background preferred next-neighbor distances can be concluded. A multilayer of water forms a thick molecular crystal of ice grown in (square-root 3 x square-root 3)R30-degrees periodicity on Pt(111).