Epitaxy on quasicrystals: metals, semi-metals and molecules

Young, Kirsty
Epitaxy on quasicrystals: metals, semi-metals and molecules. Doctor of Philosophy thesis, University of Liverpool.

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The research described in this doctoral thesis involves the experimental investigation of heteroepitaxial growth at quasicrystal surfaces. The aim is to further extend fundamental surface growth studies to such complex intermetallics and to form high quality, single-component quasicrystalline layers. The experiments included involve deposition of Cu, Bi, pentacene and carbon-60 on quasiperiodic surfaces. The formation and structure of these adsorbate layers on di�fferent quasicrystalline surfaces are analysed with surface science techniques. X-ray photoelectron spectroscopy measurements con�rmed complete �first layer followed by island growth mode of Bi on i-AlPdMn. Upon heating of the layer, stable monolayer and submonolayer coverages were observed supporting a strongly bound layer and the initial nucleation of stable, pentagonal clusters. Low energy electron di�raction patterns of the multilayer show that the {111}-rhombohedral islands are rotationally epitaxial with the substrate while the {012}-rhombohedral islands are not. The atomic structure and size of islands are measured with scanning tunnelling microscopy. A higher flux of Bi is found to inhibit the morphological transformation of the thin �film to {111}-rhombohedral islands. Scanning tunnelling microscopy of pentacene adsorption on i-AlPdMn found the molecules to be chemisorbed in a disordered, at layer at the surface. The same arrangement of molecules is observed for adsorption on a quasicrystalline Bi monolayer, while ordered rows of molecules are evidenced on the latter {012}- rhombohedral Bi islands. Pentacene formed incommensurate layers composed of dense, periodic rows, on the aperiodic vicinal Cu structure on i-AlPdMn. DFT calculations of naphthalene adsorption at the surface supported and detailed the adsorption sites of the acene along the rows. Cu exhibited 3-D cluster growth on i-AgInYb and on a pseudomorphic Bi layer at this surface. The Cu absorbs on the truncated, rhombic triacontrahedral clusters leading to some initial ordering. A pentacene monolayer on i-AgInYb successfully formed the �first epitaxial, quasiperiodic molecular overlayer to be observed experimentally. The layer is composed of many clusters with pentagonal symmetry and a large degree of orientational alignment along high symmetry directions of the substrate is observed. C60 grew in a disordered fashion on a Bi monolayer at i-AgInYb, although some local partial C60 clusters possessing 5- and 10-fold symmetry were observed at low submonolayer coverage.

Item Type: Thesis (Doctor of Philosophy)
Additional Information: Date: 2012-11 (completed)
Uncontrolled Keywords: surface physics, quasicrystals, condensed matter, adsorption, STM molecular overlayers
Subjects: ?? QC ??
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 07 Jan 2013 16:02
Last Modified: 16 Dec 2022 04:37
DOI: 10.17638/00008113
  • McGrath, Ronan
URI: https://livrepository.liverpool.ac.uk/id/eprint/8113