Showing papers by "Ronan McGrath published in 2003"

Low-energy electron diffraction from quasicrystal surfaces

Abstract: The discovery of ordered but aperiodic quasicrystal structures has required the development of new diffraction methods to determine their structures. The purpose of this review is to highlight the challenges posed by the aperiodicity of quasicrystals to the study of their surface structures by low-energy electron diffraction (LEED). This paper describes how the LEED technique has been thus far adapted to study several quasiperiodic surface structures, and summarizes the results of those studies. It also presents new spot-profile-analysis LEED results from the fivefold surface of Al–Pd–Mn. An x-ray diffraction experiment and a He-atom diffraction experiment, both on Al–Pd–Mn, are also described for comparison.

Nanostructured quasiperiodic surfaces: the origin of pentagonal hollows and their role in adsorption and nucleation processes

Abstract: Pentagonal hollows, which are imaged as dark five-fold stars, form the dominant structural motif in scanning tunnelling microscopy (STM) measurements of the five-fold surfaces of icosahedral quasicrystals. Recent progress in the understanding of these surfaces has led to a thorough understanding of these entities; we illustrate how they may be considered as truncations of the basic building blocks (i.e. Bergman clusters) of the bulk structure. The use of these pentagonal hollows as adsorption and nucleation sites is demonstrated using STM images of their filling during scanning of the clean Al–Pd–Mn surface and in the adsorption of C60 molecules and copper atoms on Al–Pd–Mn and of aluminium atoms on Al–Cu–Fe.