Synchrotron X-ray Studies of Pristine, Intercalated, and Functionalized Epitaxial Graphene on Silicon Carbide(0001)

Since its isolation in 2004, graphene has received virtually unparalleled attention from researchers in various fields. The great interest in graphene is driven in no small part by its superlative and unique electronic properties, intrinsic low dimensionality, and its potential for application in nanoelectronics. However, in order to exploit the extraordinary electronic properties of graphene, it is first necessary to develop a suitable growth method that is amenable to production at the wafer-scale. One of the most promising routes to large-scale production of graphene is via thermal extrusion of from silicon carbide. This dissertation is focused on understanding the structure of epitaxial graphene grown on the Si-terminated face of silicon carbide (EG/SiC(0001)), as well as its modified (intercalated, functionalized) forms. To do this, I employ synchrotron-based X-ray characterization techniques to investigate these structures with A-scale resolution and chemical sensitivity.;The primary objective of this dissertation is to use a novel approach to clarify long-standing uncertainties concerning the nature of the interface between EG and the SiC substrate. This interface is highly technologically relevant, and its precise structure and chemical composition have direct influence on the properties of the graphene itself. To this end, I construct a high-resolution (sub-A), chemically-sensitive atomic density map of the interfacial structure using X-ray surface scattering combined with the X-ray standing wave-enhanced photoelectron spectroscopy. Next, I switch focus to engineered EG/SiC(0001) interfacial structures, which have been observed to influence the electronic properties of the overlaying graphene. Here, I present a structural investigation of the effects of hydrogen intercalation on the interfacial structure of SiC(0001), a process that has been suggested to decouple the interfacial layer from the SiC substrate. Finally, characterization efforts are extended to a series of functionalized graphene heterostructures, with the goal of understanding the consequences of graphene integration with various electronics-relevant materials. Overall, this thesis highlights the unique power of X-ray characterization techniques in the investigation of various EG/SiC(0001) systems at the angstrom- and nanoscale. The information obtained from these measurements improves the understanding of pristine, intercalated, and functionalized EG/SiC(0001), and may help to expedite the implementation of graphene into next-generation carbon-based electronics.