THz Surface Plasmons in Wide and Freestanding Graphene Nanoribbon Arrays

Abstract

Graphene is a thin-film carbon material that has immense potential as a key ingredient in new nanoelectronic and nanophotonic devices due to its unique characteristics. In particular, plasmons in graphene appear as a practical tool for the manipulation of light with potential applications from cancer treatment to solar cells. A motivating tunability of graphene properties has been observed in graphene nanoribbons (GNRs) due to their geometrically controllable bandgaps that, in turn, influence the plasmonic properties. The formidable effort made over recent years in developing GNR-based technologies is, however, weakened by a lack of predictive approaches that draw upon available semi-analytical electromagnetic models. An example of such a framework is used here, focusing on experimentally realized GNRs from 155 to 480 nm wide and organized as two-dimensional (2D) GNR arrays. The results show that the plasmon frequency behavior is highly affected by the experimental setup or geometrical factors. In particular, the bandgap of the analyzed systems is of the order of a few meV with a density of states opening around zero energy (Fermi level) in contrast to what is observed in graphene. From the plasmonic part, it is observed in all 2D GNR arrays that the frequency–momentum trend follows a -like plasmon dispersion whose plasmon frequency can be increased substantially by increasing the ribbon width or charge density concentration. Forbidden plasmon regions are observed for high values of plasmon excitation angle or electron relaxation rate. From a sensing point of view, the important finding is the fact that 2D GNR arrays of 155 nm wide with high values of electron relaxation rate have plasmon responses similar to those observed for thrombin in water. Our predictions are projected to be of fast support for detecting plasmons in more complex designs of ribbon nanodevices with potential applications in molecular sensing of aqueous molecules.

Dataset for Electronics and Plasmonics in Graphene, Silicene, and Germanene Nanostrips

“…However, in this approach, the calculated Fermi velocity (0.86 × 10 6 m/s) fell below the experimental value for graphene (1.1 × 10 6 m/s) [28]. Despite this, we proceeded to explore the potential applications of wide GNRs in biosensing using this approach [29,30]. Recently, we have enhanced our calculations by employing the GW approximation method to investigate silicene and germanene strips [31,32].…”

“…In this context, the 2D charge density can be calculated from the Fermi level approach, as follows [29,30]:…”

Modeling Plasmonics and Electronics in Semiconducting Graphene Nanostrips

“…In our earlier reports, we estimated the plasmonic properties using conventional DFT calculations based on local density approximation (LDA), where the DFT-LDA charge-carrier velocity served as a key input parameter [20]. Additionally, we successfully employed the same approach to predict the properties of wider graphene nanostrips [22]. Moreover, we explored the potential of graphene nanostrips for molecular sensing applications [23].…”

“…Hence, our focus in studying the plasmon frequency dispersion lies in the parameter of charge density (𝑁 2𝐷 ). However, it is essential to highlight that, as demonstrated in our prior studies [20,[22][23][24], we possess the capability to explore the other critical parameters encompassed within Equation 1 with relative ease. Furthermore, the choice of 𝑁 2𝐷 as the parameter of interest is notably strategic.…”