Low-energy electron diffraction study of potassium adsorbed on Ni(111)

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Abstract
Low-energy electron diffraction (LEED) data are presented for submonolayer coverages of potassium on Ni(111) at 70 K K. Several incommensurate phases are observed which differ in their degree of order. At low coverage, rings are observed in the LEED pattern which are attributed to an amorphous solid or a fluid phase. At coverages between 0.14 and 0.22 monolayer, a hexagonal solid structure is observed which disorders into a correlated fluidlike phase before disordering completely. At a coverage of 0.25, the overlayer has a commensurate 2×2 structure, which is more stable than the incommensurate structures. The dominant interaction at all coverages appears to be the repulsive dipole interaction. Density modulations in the incommensurate layer, if they exist, are very weak. A phase diagram is presented.