- Seminar of Reconfigurable Plasmonics and Metamaterials
- Fabrication, properties and applicationsof plasmene nanosheet — Monash University
- Reviews in Plasmonics 2016
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Zhang, Chemical Society Reviews 40, ;  K. Yao and Y. Liu, Nanotechnology Review 3, ;  C.
Seminar of Reconfigurable Plasmonics and Metamaterials
Zhao et al. Li et al. Wang et al. For additional information, please contact Prof.
Fabrication, properties and applicationsof plasmene nanosheet — Monash University
Ying Li at , yingli engr. Categories: Events and Seminars , Past Seminars. Figure 5 C plots the emissivity spectra for different carrier densities. As expected, a higher carrier density sample emits more infrared light. Because the plasmon structures are nanoribbons, they are anisotropic. This has consequences, such as polarized light emission. This experiment opens an avenue for graphene plasmonic structures to be used in mid-IR light sources. A Experimental set-up for the thermal emission studies. C Doping dependence of the emissivity enhancement spectrum.
D Polarization dependence of the emissivity enhancement spectrum. A—D Reproduced with permission from [ 63 ]. Atomically thin graphene is vulnerable to the immediate environment. Many factors, such as doping and strain of graphene, can be strongly influenced by the substrate. Plasmons in graphene can be influenced to a large extent by the environment as well. For instance, the dielectric constant of the substrate is one of the determining factors for the plasmon resonance frequency [ 24 ]. Surprisingly, graphene plasmon can have very strong interaction to other atomically thin 2D materials with polar phonons.
Brar et al. Although the h-BN flake used in the study is atomically thin, the effect on the plasmon is very dramatic. Figure 6 A illustrates a graphene ribbon on the SiO 2 substrate, with a single h-BN layer in-between. The charge carrier collective oscillation and the h-BN lattice vibration are artistically sketched. Figure 6 B shows the extinction spectra of such graphene ribbons with various ribbon widths. Clearly, the graphene plasmon mode hybridizes with the h-BN polar phonon mode and the plasmon dispersion exhibits an anti-crossing behavior.
Figure 6 C presents a loss function map based on RPA calculation. Four plasmon branches and their dispersions are shown. Two polar phonons from SiO 2 and one phonon from h-BN are indicated. From the anti-crossing behavior and the splitting of the two relevant branches, it can be inferred that the coupling between graphene plasmon and h-BN phonon is in the classical electromagnetic strong coupling regime. It is an astonishing result, given the fact that the h-BN here is only one atom layer.
A Sketch for graphene plasmon and h-BN polar phonons. A bare h-BN spectrum is also shown.
C Calculated loss function map using the RPA method. Extracted plasmon frequencies are also shown as discrete points.
Reviews in Plasmonics 2016
A—C Reproduced with permission from [ 26 ]. Graphene plasmon not only can couple to external polar phonons but also couple to intrinsic ones. However, for single-layer graphene, there is no intrinsic polar phonon. AB-stacking bilayer graphene, which is typically obtained through mechanical exfoliation of bulk graphite, has a polar phonon and the plasmon in it can interact. Figure 7 A shows the absorption spectrum of a bilayer graphene without patterning into nanostructures.
The plasmon-phonon coupling strength in bilayer graphene is similar to that of graphene on single-layer h-BN. Both qualitative and quantitative behaviors are similar. Figure 7 B presents the plasmon spectra for a bilayer graphene ribbon array with various chemical doping levels. The ribbon width is designed to be nm.
The two hybrid plasmon-phonon modes show anti-crossing behavior. At certain point, when the plasmon frequency coincides with the phonon frequency, the spectrum exhibits a broad peak with a sharp dip in the center. This is the so-called phonon-induced transparency, a classical analog of the electromagnetically induced transparency EIT phenomena [ 65 ]. This phonon-induced transparency can be tuned either by chemical doping or electrostatic gating, as shown in Figure 7 B and C. A Extinction spectrum of unpatterned bilayer graphene. Top inset shows the infrared active phonon mode and the other inset illustrates the electronic transitions.
B Extinction spectra for a bilayer graphene nanoribbon array with different chemical doping levels. C Gate tuning of the bilayer graphene plasmon spectrum. A—C Reprinted with permission from [ 53 ]. Graphene shows a huge potential in photonic and optoelectronic applications [ 66 ]. By combining graphene with metal-based structures, reconfigurable metamaterials [ 67 ] and metasurfaces [ 68 ] in the terahertz frequency range have been achieved. Localized plasmons in graphene nanostructures are in the mid-IR frequency range and so are biological and organic molecule vibrational frequencies.
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As a result, graphene plasmon possesses huge potential in molecular sensing. Besides, graphene plasmon can enhance the light absorption and emission efficiency, which can be used in photodetection and light sources. Li et al. Figure 8 A presents the infrared absorption spectra of a thin layer of poly methyl methacrylate PMMA on a graphene nanoribbon array.
Both spectra for parallel and perpendicular polarizations are shown. The sharp vibration mode and the relatively broad graphene plasmon mode couple strongly and form a Fano resonance system [ 70 ], which has very strong effect on the line shape of the vibration mode depending on the relative peak frequencies of the two modes. B Extinction spectra of graphene and gold biosensors covered with a protein layer. The thick curves are the measured spectra and the thin curves are the fittings for bare graphene and gold biosensors.
D Field confinement percentage as a function of the distance from the biosensor surface for both graphene and gold. The inset is the enlarged version in the small distance d regime. E Graphene nanoribbon photodetector with electrical gate. F Gate and polarization dependence of the photoresponse for the ribbon array shown in E. The red dots are for the perpendicular polarization, whereas the blue dots are for the parallel case. A Reproduced by permission from [ 24 ]. B—D Reproduced by permission from [ 25 ]. E and F Reprinted by permission from [ 69 ]. Plasmons based on noble metals have been applied to detect biological molecules too [ 71 ].