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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2012)

Film growth is characterized by the making and breaking of chemical bonds. Other interactions such as Van der Waals and electrostatic forces are secondary if not negligible. The primary purpose of this thesis is to provide an assessment on how epitaxial growth on an inert substrate, i.e. no dangling bonds, can proceed. This is done by calculating the adsorption energy of carbon (C), silicon (Si), and germanium (Ge) adatoms at different sites on graphene sheet and mapping their potential energy surface. We observe that adsorption energy of carbon on graphene is the strongest, 1.45 eV more than that of silicon and 1.56 eV more than germanium. The second part of this thesis is observing how C, Si and Ge dimers behave on graphene. Carbon dimer still displays the strongest interaction with graphene, yet the binding strength of germanium dimer surpasses that of silicon's in these dimer simulations. All calculations are done by the ab-initio density functional theory.

    Cover page: Adsorption of Carbon, Silicon, and Germanium Adatoms on Graphene Sheet
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2014)
    The diffusion processes and kinetic barriers of individual carbon adatoms and clusters on graphene surfaces are investigated to provide fundamental understanding of the physics governing epitaxial growth of multilayer graphene. It is found that individual carbon adatoms form bonds with the underlying graphene whereas the interaction between graphene and carbon clusters, consisting of 6 atoms or more, is very weak being van der Waals in nature. Therefore, small carbon clusters are quite mobile on the graphene surfaces and the diffusion barrier is negligibly small (∼6 meV). This suggests the feasibility of high-quality graphene epitaxial growth at very low growth temperatures with small carbon clusters (e.g., hexagons) as carbon source. We propose that the growth mode is totally different from 3-dimensional bulk materials with the surface mobility of carbon hexagons being the highest over graphene surfaces that gradually decreases with further increase in cluster size.
      Cover page: On the kinetic barriers of graphene homo-epitaxy
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