The structural property and interaction of bismuth-based low-dimensional structures growth on monolayer epitaxial graphene

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Student thesis: Doctoral Thesis

Abstract

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
Date of Award2015 Jul 24
Original languageEnglish
SupervisorJung-Chun Huang (Supervisor)

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