Scanning tunnelling microscopy has been used to study the formation of a Bi monolayer deposited on the five-fold surface of i -Al70Pd21Mn9. Upon deposition of low sub-monolayer coverages, the nucleation of pentagonal clusters of Bi adatoms of edge length 4.9Å is observed. The clusters have a common orientation leading to a film with five-fold symmetry. By inspection of images where both the underlying surface and the Bi atoms are resolved, the pentagonal clusters are found to nucleate on pseudo-Mackay clusters truncated such that a Mn atom lies centrally in the surface plane. The density of these sites is sufficient to form a quasiperiodic framework, and subsequent adsorption of Bi atoms ultimately leads to the formation of a quasicrystalline monolayer. The initial nucleation site is different to that proposed on the basis of recent density functional theory calculations.
Lead has been deposited on the ten-fold surface of decagonal Al 72 Ni 11 Co 17 to form an epitaxial quasicrystalline single-element monolayer. The overlayer grows through nucleation of nanometer-sized irregular islands and the coverage saturates at 1 ML. The overlayer is well-ordered quasiperiodically as evidenced by LEED and Fourier transforms of STM images. Annealing the film to 600 K improves the structural quality, but causes the evaporation of some material such that the film develops pores. Electronic structure measurements using X-ray photoemission spectroscopy indicate that the chemical interaction of the Pb atoms with the substrate is weak.
Copper deposited on the five-fold surface of icosahedral Al-Pd-Mn forms domains of a structure whose surface has a one-dimensional aperiodic modulation. It is shown that C60 deposited on this aperiodic film has highly reduced mobility as compared to C60 deposited on periodic Cu surfaces. This finding is explained in terms of the recently proposed structural model of this system.
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Complex metallic alloy / Structure / Surface / LEED / STM Abstract. Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) results are used to study the pseudo-6-fold nature of the (100) surface of the orthorhombic quasicrystal approximant Al 4 (Cr, Fe). LEED patterns are also presented from the pseudo-10-fold (010) surface of this material. In each case the results are compared with the known bulk structure of this complex metallic alloy.
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