C-60 adsorption on the quasicrystalline surface of Al70Pd21Mn9

Room temperature adsorption of C-60 on the flat quasicrystalline surface of Al70Pd21Mn9 has been investigated using scanning tunnelling microscopy. A dispersed overlayer is formed at low coverage, with avoidance of step-edges . There is no evidence of island formation or clustering. As the coverage i s increased, a higher density layer is formed with no evidence of the forma tion of hexagonal ordered adsorbate structures seen on other substrates. Th is is followed by the onset of second layer formation. A range of bonding s ites for C60 molecules is implied from measurements of apparent molecular h eights and from thermal effects. Detailed analysis of the surface at a low coverage (similar to0.065 ML) provides evidence of adsorbate local order, w ith Fibonacci (iota -scaling) relationships between the C-60 molecules. Whe re this occurs, the preferred adsorption site is tentatively identified as the pentagonal hollow. These local correlations however are not found to ex tend over larger regions of the surface. (C) 2001 Elsevier Science B.V. All rights reserved.