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Single Layer Nanomaterials: The Chemical Vapor Deposition Synthesis and Atomic Scale Characterization of Hexagonal Boron Nitride and Graphene

Abstract

The design of novel nanomaterials with tunable geometries and properties has transformed chemistry and physics in recent years. In particular, recent advances in the isolation of two-dimensional films have inspired the exploration and development of stable, self-supporting single layer systems. Most notably graphene, a single layer of hexagonal sp2 carbon, has attracted interest due to intriguing electronic, optical, and mechanical properties. Hexagonal boron nitride (h-BN) is a closely related two- dimensional material, isoelectronic with graphene but often exhibiting very different electronic characteristics. The production of these monolayer materials has revealed exciting new properties that arise due to constrained geometry at the nanoscale.

This dissertation explores the atomic scale properties of low-dimensional hexagonal nanomaterials, with a particular focus on hexagonal boron nitride (h-BN), graphene, and related materials. The synthesis processes for hexagonal boron nitride, graphene, nanotubes and nanoribbons will be discussed, with a particular emphasis on chemical vapor deposition. By controlling the number of layers in two-dimensional materials, we can tune their properties for new applications. The fabrication, characterization, and functionalization of additional low-dimensional nanomaterials including nanoribbons, nanotubes, and the composite materials that contain them will also be introduced.

In nanoscale systems, material properties are heavily influenced by atomic structure and defects. This dissertation will discuss the investigation of h-BN and graphene at the atomic scale, with a particular emphasis on defects studied by atomic resolution transmission electron microscopy. Further probing the dynamics of these atomic defects includes in situ imaging and heating from room temperature up to 1000°C. Under these extreme conditions, novel defect structures and dynamics have been observed.

In the coming years, these materials will continue to revolutionize the way we think about nanoscale materials, and are likely to be implemented into a variety of new and emerging technologies.

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