Graphene is often regarded as a “miracle material” by physicists. Composed of a layer of carbon exactly one atom thick, it has a plethora of potential applications. In the less than ten years, publications numbering in the ten thousands have been released about graphene. Against this background, the Colorado School of Mines’ own Dr. Zhigang Wu recently presented new research on “Band Gap Opening of Graphene with Periodic Structural Modifications.”
Many, though not all, of graphene’s properties are favorable for practical use. Graphene ‘s electron mobility, thermal conductivity, Young’s modulus, and optical absorption are very good, but it has certain difficulties for application. Most significantly, it has no inherent band gap opening, a very small on-off ratio in field-effect transistors, and excitations do not always last long enough for use. Therefore, a major focus of graphene research is in making graphene a semi-conductor so it can be used in place of more common semi-conductors like silicon.
Several options exist already to manipulate graphene into a semi-conductor, including graphene nanoribbons and periodic defects. However, the focus of Wu’s presentation was on a new technology, graphene nanomesh. This material is created by poking regular holes in a sheet of graphene and can be used for field-effect transistors.
As a computational physicist, Wu worked to connect the theoretical underpinnings of graphene with practical experimental results. Wu successfully demonstrated that the created band gap opening could be modeled analytically “mapping the discrete perturbative reciprocal lattice vectors onto Dirac points.”
The presented model “used delta function potential to model periodic perturbation” and match Dirac points.
Wu’s research also mapped graphene nanomesh to carbon nanotubes and graphene nanoribbons. The model used rectangular and 60-degree parallelogram unit cells to map band gap to carbon nanotubes and graphene nanoribbon. Mapping found that rectangular and hexagonal unit cells both show an exactly reverse correspondence between the graphene nanomesh and the carbon nanotubes. This results from the fact that the Dirac points should be matched to create an semi-conductor in one sort of material and avoided in the other. Wu mentioned these results were confirmed by discrete Fourier analysis, but that he hoped future work would move to other analysis methods.
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