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Title: Diamond-graphene surface and interfacial adsorption studies
Keywords: adsorption, diamond, epitaxial graphene, surface science, density functional theory
Issue Date: 18-Jan-2010
Citation: HOH HUI YING (2010-01-18). Diamond-graphene surface and interfacial adsorption studies. ScholarBank@NUS Repository.
Abstract: In this age of nanoscience and technology, due to reduction of device sizes, the surface of a material or interface of composite plays a crucial role in determining its properties. With a myriad of forms, carbon-based materials offer a number of new and exciting possibilities for both scientific research and practical applications. In this thesis, we investigated diamond surfaces and graphene through a combination of theoretical simulation and experimental efforts to provide the best possible elucidation. The surface chemistry of diamond and graphene, as well as the interfacial binding between diamond and graphene, was investigated with a view towards understanding how bonding affects the electronic properties of these condensed carbon phase. The reconstructed diamond (100) and (111) surfaces are found to be reactive templates for chemical functionalization, thus it is possible to assemble molecules or functionalities of interest on the diamond surface in a controlled fashion. In the case of the diamond (111) surface, this is the first experimental and theoretical evidence for such reactions. The possibility of tailor-made surface termination is invaluable to the realization of diamond applications in molecular electronics. The binding of organic molecules on metallic graphene, a monolayer sheet of carbon, can induce a band gap opening. This is important for tuning the electronic properties of graphene. Cycloaddition of allyl organics on the dimer rows of the clean C(100)-2×1 diamond surface is confirmed by sticking probability measurements and density functional theory (DFT) calculations, whereas cycloaddition of aromatic molecules on the Pandey chain of the clean C(111)-2×1 diamond surface is validated by high-resolution electron-loss spectroscopy (HREELS) and DFT calculations. Chemical modification also gives rise to an induced dipolar layer that modifies the electrostatic potential outside the surface, thus the functionalized diamond surface exhibited negative electron affinity similar to hydrogenated diamond surfaces. The diamond-graphene interface is an interesting model for building pure carbon-based electronics and thus this model is too investigated to understand the structure at the interface. We also present a methodology for the growth and characterization of epitaxial graphene. The quality of our samples is verified by in situ reflection high-energy electron diffraction (RHEED), Raman spectroscopy, HREELS and electrochemical studies. Finally, we demonstrate a simple method for tuning the band gap of graphene: non-covalent functionalization. DFT calculations and nonlinear optical properties of functionalized EG provided evidence for the opening of a band gap. This effect is due to a breaking of the six-fold symmetry in graphene, brought about by the p-p interaction between graphene and aromatic adsorbates.
Appears in Collections:Ph.D Theses (Open)

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