Rare gases physisorbed on Pt(111):: a low-temperature STM investigation

The structure and the phase transitions of Xe, Kr and Ar physisorbed on Pt(1 1 1) in the submonolayer-coverage range has been explored by low-temperature scanning tunneling microscopy. The hexagonal incommensurate rotated (HIR) hexagonal incommensurate (HI) transition with decreasing Xe coverage has been observed unambiguously. The onset of adlayer rotation occurs for Xe islands larger than 700 Angstrom(2). Xe dimers physisorbed on Pt(1 1 1) are commensurately ordered on the Pt(1 1 1) surface. The experimental results are compared to molecular dynamic simulations. The orientation of the high order of commensurability (HOC) Kr structure with respect to the surface strongly depends on the terrace width and on the step morphology. Kr monolayer misorientation ranging from 0degrees to 30degrees has been observed depending on the surface morphology. The Ar monolayer adopts a HOC structure aligned with respect to the Pt(1 1 1) surface while for low coverage, the most energitically favorable position of the Ar islands corresponds to a R(1.875 x n)degrees (n an integer) HI structure. (C) 2002 Published by Elsevier Science B.V.