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Graphene Photonic Properties and Applications
Published in Yaser M. Banadaki, Safura Sharifi, Graphene Nanostructures, 2019
Yaser M. Banadaki, Safura Sharifi
The contributions of intraband and interband transitions in the optical conductivity significantly depend on the carrier density, so that each part has different strength at different frequency ranges. These contributions are also directly related to the chemical potential in graphene. Figure 9.4 describes the optical conductivity of graphene and its equivalent refractive index as a function of the chemical potential and the wavelength of incident light. For undoped suspended graphene (i.e., there is no electric field to tune the chemical potential), the interband transitions are responsible for the ∼2.3% broadband absorption. The DC electric field bias tunes the chemical potential in graphene, adding either electrons or holes to the system. In this scenario, the interband transitions of electrons occur only for 2E0 = ħω > 2EF, while other transitions are forbidden or blocked for E0 < 2EF, as shown in Fig. 9.4a. The absorption due to the interband transition is reduced by Pauli blocking, because the vacant states in conduction band are all occupied when the pumping light is intense enough for a specific relaxation process [37]. The intraband transitions are mainly responsible for the absorption in the far-infrared and also contribute, to some extent, to the mid-infrared optical response [63]. For short wavelengths in the visible range, graphene’s optical conductivity is dominated by interband transitions [63]. The contribution of intraband transition decreases by increasing the chemical potential in the visible range and has, therefore, no significant effect on graphene’s optical conductivity at these wavelengths.
First-principles study of rocksalt Mg x Zn1− x O: band structure and optical spectra
Published in Philosophical Magazine, 2020
Nidhal Drissi, Ahmed Gueddim, Nadir Bouarissa
The optical conductivity is a property of materials that relates the current density to the electric field for general frequencies. Figure 7 displays the optical conduction spectra of rocksalt MgxZn1−xO (0 ≤ x ≤ 1) as a function of photon energy. We observe that for rocksalt ZnO (x = 0) the optical conduction is strongly linked to the photon incident energy (wave-length). It is almost zero up to around 3.7 eV and then increases with the increase of the photon frequency (energy) where it reaches its maximum for a photon energy lying between 9-11 eV, and vanishes for photon energies beyond almost 14 eV. By increasing the alloy composition x, the optical conductivity spectrum of rocksalt ZnO shifts towards higher photon energies. The shift becomes more important when reaching the rocksalt MgO. The maximum of the optical conduction of MgxZn1−xO (0 < x ≤ 1) decreases with respect to that of rocksalt ZnO and is shifted towards higher photon energies. The spectra are vanished for photon energies larger than 14 eV. The effect of changing the Mg content x appears to be more important for photon energies in the range 7–14 eV. The change in the optical conductivity by varying the alloy composition x reflects the change in the rate at which electrons absorb incident photons for selected energy.
Physical properties of molybdenum monoboride: Ab-initio study
Published in Philosophical Magazine, 2018
Priyanka Rajpoot, Anugya Rastogi, U. P. Verma
Optical conductivity is a powerful tool to measure electronic states of materials. The term ‘optical conductivity’ means the electrical conductivity in the presence of an alternating electric field. When light falls on the material surface, it shows optical conductivity. Figure 6(e) shows the conductivity spectra as a function of photon energy. From figure we see that conductivity starts from zero photon energy, which indicates that MoB has metallic nature. The highest peak of conductivity, 13.018 × 103 Ω−1 cm−1 appearing at 4.93 eV corresponds to σyy(ω). The another peaks of conductivity 11.831 × 103 and 11.493 × 103 Ω−1 cm−1appearing at 4.93 and 4.44 eV, respectively, correspond to σxx(ω) and σzz(ω). Overall MoB is more conductive for incident photon energy range between ~1 and 12 eV.
Influence of Pt and P doping on the performance of g-C3N4 monolayer
Published in Materials and Manufacturing Processes, 2020
Deepak Kumar Gorai, Tarun Kundu
The optical conductivity curves also confirmed the observed behaviors of the α, as shown in Fig. 5d. Optical conductivity is a vital tool for the study of electronic states in materials. A redistribution of charge occurs when a system is put through to an external electric field, which results in current induction.