Inducing anisotropy in graphene by interfacing with carbon systems

Imposing long-range periodicity on top of the underlying crystal structure of graphene allows for the tunability of its physical properties. Graphene fabricated with a periodic array of nanoscale holes, for example, has a large band gap and is expected to exhibit anisotropic optical and electrical properties.

Antidormi and Cummings explore the possibility of interfacing graphene with other anisotropic carbon systems, such as nanoporous graphene (NPG) and arrays of graphene nanoribbons (GNRs), to alter its features. Using numerical methods, they confirmed this type of induction of anisotropy in graphene is indeed achievable, while also maintaining the material’s Dirac-like band structure.

“Our results show by making it anisotropic, graphene may be used for long-wavelength optical polarimetry in the midinfrared and beyond,” said author Aron William Cummings. “This could be applied to the imaging of tissue samples, the analysis of astronomical phenomena, or the identification of hidden objects, aka scene detection. The latter may apply to the detection of land mines, for example.”

The researcher’s simulations revealed interfacing with NPG and GNRs induced an anisotropy of 20% to 50% in the material’s Fermi velocity, optical absorption, and electrical transport. The degree of induced anisotropy predictably depends on the band gap of the carbon systems.

However, it was strongly influenced by specific features of each system — for example, the width between pores in NPG or a benzene ring bridge instead of a single carbon-carbon bond connecting the GNRs. This finding could mean larger effects may be discovered by using some other NPG- or GNR-based structure that hasn’t been considered yet.

Source: “All-carbon approach to inducing electrical and optical anisotropy in graphene,” by Aleandro Antidormi and Aron William Cummings, AIP Advances (2021). The article can be accessed at http://doi.org/10.1063/5.0062521 .