Surface/interface modification and characterization of C-face epitaxial graphene
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Graphene has been one of the most interesting and widely investigated materials in the past decade. Because of its high mobility, high current density, inherent strength, high temperature stability and other properties, scientists consider it a promising material candidate for the future all-carbon electronics. However, graphene still exhibits a number of problems such as an unknown interface structure and no sizable band gap. Therefore, the purpose of this thesis is to probe and solve these problems to make graphene suitable for electronics. The work focuses on high-quality C-face epitaxial graphene, which is grown on the (000-1) face (C-face) of hexagonal silicon carbide using the confinement-controlled sublimation method. C-face epitaxial graphene has much higher mobility compared to Si-face graphene, resulting from its special stacking order and interface structure, the latter of which is not fully understood. Thus, the first part of the work consists of a project, which is to investigate and modify the interface and the surface of C-face graphene by silicon deposition and annealing. Results of this project show that silicon can intercalate into the graphene-SiC interface and form SiC by bonding carbon atoms on the graphene surface. Another crucial problem of graphene is the absence of a band gap, which prevents graphene from becoming an ideal candidate for traditional digital logic devices. Therefore, the second project of this work is devoted to introducing a wide band gap into the graphene electronic structure by growing from a nitrogen-seeded SiC. After successful opening of a band gap, a pre-patterning method is applied to improve graphene thickness variations, orientational epitaxy, and the gapped electronic structure.