Quasi-ordered C₆₀molecular films grown on the pseudo-ten-fold (1 0 0) surface of the Al₁₃Co₄quasicrystalline approximant

Abstract

The growth of C60 films on the pseudo-tenfold (100) surface of the orthorhombic Al13Co4 quasicrystalline approximant was studied experimentally by scanning tunneling microscopy, low-energy electron diffraction and photoemission spectroscopy. The (100) surface terminates at bulk-planes presenting local atomic configurations with five-fold symmetry-similar to quasicrystalline surfaces. While the films deposited at room temperature were found disordered, high-temperature growth (up to 693 K) led to quasi-ordered molecular films templated on the substrate rectangular unit mesh. The most probable adsorption sites and geometries were investigated by density functional theory (DFT) calculations. A large range of adsorption energies was determined, influenced by both symmetry and size matching at the molecule-substrate interface. The quasi-ordered structure of the film can be explained by C60 adsorption at the strongest adsorption sites which are too far apart compared to the distance minimizing the intermolecular interactions, resulting in some disorder in the film structure at a local scale. Valence band photoemission indicates a broadening of the molecular orbitals resulting from hybridization between the substrate and overlayer electronic states. Dosing the film at temperature above 693 K led to molecular damage and formation of carbide thin films possessing no azimuthal order with respect to the substrate.

The role of three-dimensional bulk clusters in determining surface morphologies of intermetallic compounds: Quasicrystals to clathrates

“…In fact, DFT calculations have highlighted two strong adsorption configurations: one with the hexagonal face of the C 60 molecule facing the center of one Al bipentagonal motif located slightly below the mean position of the surface plane and a second with, indeed, the pentagonal C 60 face parallel to the surface in between the two sets of Al bipentagonal motifs. 101 Due to steric considerations, both sites cannot be populated simultaneously, explaining part of the disorder observed in the molecular film. For high-temperature deposition and low coverage, the fullerenes gather into elongated islands aligned in specific directions, which alternate on adjacent terraces.…”

“…Once completed, the quasiordered and rumpled C 60 film adopts the orthorhombic unit mesh of the substrate. 101…”

A Critical Review on Al-Co Alloys: Fabrication Routes, Microstructural Evolution and Properties

“…Another field of high interest for Al-Co alloys that attracted a lot of attention is the surface, catalytic and transport properties of Al-Co intermetallic compounds [24][25][26][27][28][29][30][31][32][33]. During the last decade, the focus shifted on the fabrication of bulk Al-Co alloys, using non-equilibrium techniques such as vacuum arc melting, and the assessment of their surface degradation properties.…”