Conjugated carbon monolayer membranes - synthesis and integration techniques

摘要

The existence of graphene, a single sheet of graphite and the simplest class of conjugated carbon monolayer, discovered in 2004, has attracted immensely interests from scientific community. The research in this area has grown exponentially attributed to its exceptionally high electron mobility, high elastic moduli, and observations of unconventional phenomena in physics. Unfortunately, the original technique for producing graphene sheet on insulating substrates, i.e. by mechanical exfoliation from a piece of graphite, is not scalable. Hence, it is utmost important to find approaches for producing large area graphene or improving film transfer quality. It is also interesting to explore other types of related two-dimensional materials. The first part of this dissertation describes a strategy for the synthesis of a class of conjugated carbon monolayer membranes. The process starts with the formation of self-assembled monolayer of alkyne-containing monomers on flat or structured solid support such as silicon oxide and silicon nitride followed by chemical crosslinking within monolayer. Once linked, the membranes are robust enough to be released from the support and transferred to other surfaces. Likewise, three-dimensional objects, such as balloons and cylinders, with monolayer thickness can be generated with similar method. The second part focuses on graphene layer which is epitaxially grown on SiC wafer. This growth technique has been known for producing large-area graphene films, but the graphene film is required to be exploited on the growth substrate due to unavailability of transfer procedure. I adopted and improved the techniques, used for transferring carbon nanotube, to transfer graphene films from SiC substrates to arbitrary substrates. The technique utilized a bilayer film of either gold/polyimide or palladium/polyimide as a transfer element. The properties of transferred film were characterized by different techniques including Raman spectroscopy, SEM, AFM and STM. I finally fabricated simple devices on this transferred graphene sheet to measure electrical properties of the film.