Quasicrystalline surface order on decagonal Al72.1Ni11.5Co16.4: An investigation with spot profile analysis LEED

The quasicrystalline order of a decagonal, Co-rich AlNiCo alloy was investi gated using spot profile analysis low energy electron diffraction (SPA-LEED ). The surface gives rise to a tenfold diffraction pattern with the peak po sitions being related by the golden mean, indicating quasicrystallinity in the surface region. From the half-widths of the specular spot as a function of the electron energy, the step height was determined to be (2.05 +/- 0.0 5) Angstrom, a value which agrees with the bulk distance of the fivefold qu asiperiodic planes of 2.04 Angstrom. Kinematic model calculations revealed that the cluster structure of the bulk is intact also in the surface region . The existence of broad features in the diffraction pattern points to a ce rtain degree of lateral disorder within the terraces. (C) 2000 Elsevier Sci ence B.V. All rights reserved.