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Dominance of short-range-order effects in low-energy electron-diffraction intensity spectra

1992; American Physical Society; Volume: 45; Issue: 23 Linguagem: Inglês

10.1103/physrevb.45.13595

1095-3795

P. Hu, Colin Barnes, D. A. King,

Surface and Thin Film Phenomena

Using low-energy electron-diffraction (LEED) formalism, we demonstrate theoretically that LEED I-V spectra are characterized mainly by short-range order. We also show experimentally that diffuse LEED (DLEED) I-V spectra can be accurately measured from a disordered system using a video-LEED system even at very low coverage. These spectra demonstrate that experimental DLEED I-V spectra from disordered systems may be used to determine local structures. As an example, it is shown that experimental DLEED I-V spectra from K/Co {101\ifmmode\bar\else\textasciimacron\fi{}0} at potassium coverages of 0.07, 0.1, and 0.13 monolayer closely resemble calculated and experimental LEED I-V spectra for a well-ordered Co{101\ifmmode\bar\else\textasciimacron\fi{}0}-c(2\ifmmode\times\else\texttimes\fi{}2)-K superstructure, leading to the conclusion that at low coverages, potassium atoms are located in the fourfold-hollow sites and that there is no large bond-length change with coverage.