1/f Noise in epitaxial sidewall graphene nanoribbons
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O. Vail↗
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Nanoscale Fabrication of Microwave Detectors from Commercially-Available CVD-Grown Monolayer Graphene
Using commercially-available monolayer graphene, synthesized by means of chemical vapor deposition, microwave power sensing elements have been nanofabricated and integrated with microwave-grade test structures suitable for on-wafer probing. The graphene, situated on a thermal oxide, was first cleaned of stray contaminants in a forming gas environment briefly held at 250 degrees Celsius using a rapid thermal annealer. Immediately following this step, the graphene was passivated with a protective aluminum oxide layer (approximately S nm in thickness). Micrometer-scale Corbino disc test structures were then fabricated in direct contact with the graphene using a self-aligned process, which relies on the fact that tetramethylammonium hydroxide develops the photoresist while removing the aluminum oxide. Graphene nanoribbons (with widths as small 400 nm) were then fabricated across the Corbino disc gaps using electron-beam writing in conjunction with a negative tone resist. The same developer exposed the majority of the graphene while defining nanometer-scale lines of photoresist stacked upon aluminum oxide. These stacks served as etch-stops while the unprotected graphene was ion-milled in an oxygen plasma. Finally, the photoresist was removed leaving behind passivated graphene nanoribbons. Damage caused by the fabrication was evaluated by comparing the Raman spectra of the grapheme before and after processing.
detectors↗
Equilibrium Limit of Boundary Scattering in Carbon Nanostructures: Molecular Dynamics Calculations of Thermal Transport
It is widely known that graphene and many of its derivative nanostructures have exceedingly high reported thermal conductivities (up to 4000 W/mK at 300 K). Such attractive thermal properties beg the use of these structures in practical devices; however, to implement these materials while preserving transport quality, the influence of structure on thermal conductivity should be thoroughly understood. For graphene nanostructures, having average phonon mean free paths on the order of one micron, a primary concern is how size influences the potential for heat conduction. To investigate this, we employ a novel technique to evaluate the lattice thermal conductivity from the Green-Kubo relations and equilibrium molecular dynamics in systems where phonon-boundary scattering dominates heat flow. Specifically, the thermal conductivities of graphene nanoribbons and carbon nanotubes are calculated in sizes up to 3 microns, and the relative influence of boundary scattering on thermal transport is determined to be dominant at sizes less than 1 micron, after which the thermal transport largely depends on the quality of the nanostructure interface. The method is also extended to carbon nanostructures (fullerenes) where phonon confinement, as opposed to boundary scattering, dominates, and general trends related to the influence of curvature on thermal transport in these materials are discussed.
Haskins, Justin↗
Single-Step, Solvent-Free, Catalyst-Free Preparation of Holey Carbon Allotropes
Methods for forming holey carbon allotropes and graphene nanomeshes are provided by the various embodiments. The various embodiments may be applicable to a variety of carbon allotropes, such as graphene, graphene oxide, reduced graphene oxide, thermal exfoliated graphene, graphene nanoribbons, graphite, exfoliated graphite, expanded graphite, carbon nanotubes (e.g., single-walled carbon nanotubes, double-walled carbon nanotubes, few-walled carbon nanotubes, multi-walled carbon nanotubes, etc.), carbon nanofibers, carbon fibers, carbon black, amorphous carbon, fullerenes, etc. The methods may produce holey carbon allotropes without the use of solvents, catalysts, flammable gas, additional chemical agents, or electrolysis to produce the pores (e.g., holes, etc.) in the carbon allotropes. In an embodiment, a carbon allotrope may be heated at a working window temperature for a working period of time to create holes in the carbon allotrope.
Lin, Yi↗