Münster 1999 – wissenschaftliches Programm
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O: Oberflächenphysik
O 29: Adsorption an Oberfl
ächen (V)
O 29.6: Vortrag
Donnerstag, 25. März 1999, 15:45–16:00, S10
Anisotropic chain structures and their phase transitions: Li on Mo(112). — •H. Pfnür2, A. Fedorus1, V. Koval1, D. Kolthoff2, I. Lyuksyutov3, and A. Naumovets1 — 1Inst. of Physics, Ukrainian Academy of Sciences, Kiev — 2Institut für Festkörperphysik, Universität Hannover — 3Texas A&M University
Alkali and alkaline-earth metals are known to form ordered chain structures on open surfaces like Mo(112), which has a row-like structure. The system Li/Mo(112) forms (1× 4), (1× 2) and incommensurate ordered structures in the first monolayer [1]. The chains of the commensurate structures are oriented perpendicular to the close-packed rows of the substrate, whereas the adsorbate forms incommensurate gradually compressed rows parallel to the substrate rows at coverages above 0.5. We measured the half widths of the LEED profiles and determined the phase diagram for the whole range of the first monolayer. (1× 4) and (1× 2) structures exhibit continuous order phase transitions to disorder. The rows of the incommensurate structures for coverages, Θ, between 0.67 and 0.9 show correlations that are compatible with the introduction of solitons starting from the rectangular unit cell with close packed Li rows at Θ = 0.90. First results of the effect of additional small concentrations (0.1 ML) of Dy as defects will also be presented.
[1] M.S. Gupalo, V.K. Medvedev, B.M. Palyukh, and T.P. Smereka, Sov. Phys. Sol. State 21 (1979) 568.