| Summary: | 博士 === 國立成功大學 === 物理學系 === 103 === To improve graphene-based multifunctional devices at nanoscale, a stepwise and controllable fabrication procedure must be elucidated. In this thesis, we have firstly demonstrated that long-range electronic interaction between Bismuth (Bi) adatoms on graphene formed on a 4H-SiC (0001) substrate at room temperature (T=300K). Using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we have elucidated that such oscillatory interaction results mainly from the mediation of graphene Dirac-like electrons and the effect of the corrugated surface of SiC substrate. These two factors cause the observed oscillatory interaction with characteristic distribution distances and linear arrangements of Bi adatoms.
Furthermore, with coverage-variation, a series of structural transition of Bi adatoms, adsorbed on monolayer epitaxial graphene (MEG), is then explored at room temperature. Bi adatoms undergo a structural transition from one-dimensional (1D) linear structures to two-dimensional (2D) triangular islands and such 2D growth mode is affected by the corrugated substrate. Upon Bi deposition, a little charge transfer occurs and a characteristic peak can be observed in the tunneling spectrum, reflecting the distinctive electronic structure of the Bi adatoms. When annealed to ~500K, 2D triangular Bi islands aggregate into Bi nanoclusters (NCs) of uniform size. A well-controlled fabrication method is thus demonstrated. The approaches adopted herein provide perspectives for fabricating and characterizing periodic networks on MEG and related systems, which are useful in realizing graphene-based electronic, energy, sensor and spintronic devices.
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