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 investigated using spot profile analysis low energy electron diffraction (SPA-LEED). The surface gives rise to a tenfold diffraction pattern with the peak positions 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 +/- 0.05) Angstrom, a value which agrees with the bulk distance of the fivefold quasiperiodic 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 certain degree of lateral disorder within the terraces. (C) 2000 Elsevier Science B.V. All rights reserved.