Engineering of carbon electronic devices using focused electron beam induced deposition (FEBID) of graphitic nanojoints
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This thesis concerns development and characterization of the FEBID technique to improve interfacial properties at MWCNT/graphene-metal junctions by forming graphitic nanojoints using hydrocarbon precursors. A fabrication protocol for ultralow-resistant, Ohmic contacts at MWCNT-metal junctions with FEBID graphitic nanojoints was developed, based on an in-depth topological/ compositional/electrical material characterization, yielding high performance “end” contacts to multiple conducting channels of MWCNT interconnect. Using the FEBID technique as a contact fabrication tool, three fabrication strategies of electrical contacts between the mechanically exfoliated multilayer graphene and a metal interconnect using graphitic nanojoints were proposed and demonstrated experimentally, suggesting one of them, the post-deposited FEBID graphitic interlayer formation, as the most efficient strategy. A patterned CVD grown monolayer graphene, which is a promising material for large area graphene device fabrication, was contacted to metal electrodes through the FEBID graphitic interlayer, whose formation and chemical coupling to graphene and metal were theoretically and experimentally explored. The effects of FEBID process on the graphitic interlayer formation and graphene electronic devices were demonstrated through electrical measurements, including the transmission line method (TLM) measurements for separate evaluation of sheet and contact resistances. Modifications of the graphene channel as well as interfacial properties of the graphene-metal junctions were achieved, highlighting a unique promise of the FEBID technique as a tool for enhancing chemical, thermo-mechanical, and electrical properties of graphene-metal interfaces along with controllable tuning of doping states of the graphene channel.