Optical properties of graphene structures (original) (raw)
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Electronic and optical properties of monolayer and bilayer graphene
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2010
The electronic and optical properties of monolayer and bilayer graphene are investigated to verify the effects of interlayer interactions and external magnetic field. Monolayer graphene exhibits linear bands in the low-energy region. Then the interlayer interactions in bilayers change these bands into two pairs of parabolic bands, where the lower pair is slightly overlapped and the occupied states are asymmetric with respect to the unoccupied ones. The characteristics of zero-field electronic structures are directly reflected in the Landau levels. In monolayer and bilayer graphene, these levels can be classified into one and two groups, respectively. With respect to the optical transitions between the Landau levels, bilayer graphene possesses much richer spectral features in comparison with monolayers, such as four kinds of absorption channels and double-peaked absorption lines. The explicit wave functions can further elucidate the frequency-dependent absorption rates and the comple...
Many-body effects in optical response of graphene-based structures
International Journal of Quantum Chemistry
Graphene is an exciting material for optoelectronics and plasmonics. Its optical response may be changed under mechanical action, such as stretching or corrugation, and with confinement of a size in a certain direction. Theoretical investigations play an important role in interpretation of experimental data and stimulating a search for novel graphene architectures. Thereby, it is important to analyze restrictions of modern approaches in calculation of optical properties of graphene-based objects and, particularly, to reveal an impact of electron-electron and electron-hole interactions on the position and shape of optical features. Here, we review the recent progress in quantum-chemical calculations of monolayer and few-layer graphenes, graphene ripples, and dots in a light of optical excitations. V
Graphene: Electronic and Photonic Properties and Devices
Nano Letters, 2010
Graphene is in many respects a nanomaterial with unique properties. Here I discuss the electronic structure, transport and optical properties of graphene, and how these are utilized in exploratory electronic and optoelectronic devices. Some suggestions for needed advances are made.
1 Electronic Transport and Optical Properties of Graphene
2014
The enormous list of publications on transport measurements in graphene starts with the seminal papers by the groups from Manchester and Columbia [1a]. Already these studies indicated a very robust transport behavior, which is characterized by a “V”-shaped conductivity with respect to charge density n and a minimal conductivity σmin ≈ 4e2∕h at the charge neutrality point n = 0. In the presence of a magnetic field, there are Shubnikov–de Haas oscillations for the longitudinal conductivity σxx and quantum Hall plateaux for the Hall conductivity σxy at a sufficiently strong magnetic field. These properties have been confirmed subsequently by various experimental groups in more detailed studies and measurements under various conditions and for different types of samples. Many of those results are collected and discussed in a number of extensive reviews [2–4]. Optical properties of graphene for light with frequency ω are (directly) related to the optical (or AC) conductivity σAC xx (ω). ...
In this paper, multi-structural optical devices are designed based on graphene tri-layer sheets using finite deference time domain (FDTD) method with surface boundary condition (SBC). The perfectly matched layer (PML) absorbing boundary condition is also used with FDTD SBC to terminate the computational space. Numerical demonstration of plasmon polaritons (SPPs) wave propagating along variety shaped tri-layer graphene sheets is presented of the proposed method by means of utilizing the gate voltage dependent property of graphene. Finally, the theoretical fabrication of a straight line interferometer, L-shaped optical waveguide and T-shaped optical splitter based on the proposed model is presented. The paper provides an effective technique in modeling multi-layer graphene based high-speed and ultra-compact optical devices.
2016
With the fast growing research and applications of graphene in photonics, understanding its properties and their correlation over broad spectral range is essential. The study presented herein is an analysis of optical conductivity and absorbance of chemical vapour deposition (CVD) single layer graphene (SLG). Optical transmittance measurements of the SLG module were performed over photon energy range from nearultraviolet (NUV, 300 nm) to near-infrared (NIR, 2500 nm) spectral regions. For photon wavelengths between 380 and 750 nm, graphene yielded an average transmittance of 97.6% with a maximum transparence peak of 98.3% at 710 nm wavelength. These results compares favorably with the reported theoretical ( ) T of 97.7%. Arguably, the numerical value of optical conductivity, for SLG (expressed in terms of universal optical conductivity, o ), equates to the absorbance (in units of ). Within the visible region, / o = 1.04, which shows a close approximation of to o . How...
Optical Properties of Bilayer Graphene Nanoflakes
The Journal of Physical Chemistry C, 2014
The optical properties of coupled graphene nanoflakes are investigated theoretically within the framework of Hartree−Fock based semiempirical methods, with the aim of unraveling the role of π−π interactions. Two different types of π-stacking are considered, obtained either by coupling two identical flakes with different relative displacement or by coupling flakes having different width or edge functionalization, i.e., with different electronic gap or ionization potential. Our results indicate that a systematic red shift and broadening of lowest excitations occur: an overall widening of the optical absorption range can therefore be expected in an ensemble of flakes. However, the coupling prevents a strong enhancement of the absorption intensity. In the case of a heterogeneous ensemble of flakes, the possibility of introducing low-energy excitations with considerable charge transfer character is also demonstrated by properly exploiting the chemical edge functionalization.
Physical Review B, 2016
We present an experimental investigation on the universality of the optical transmittance of mono-and multilayer chemically exfoliated graphene flakes. By varying the exfoliating solvent, and thereby modulating the strength of electron-electron interactions, we find that the universality is not impacted over the visible region. The impact of modulating the interaction strength is clearly seen as shifts in the M-point exciton spectra. These shifts can then lead to a reduction in the wavelength regime over which universal wavelength independent optical transmittance is observed. At the level of first-order perturbation theory, our results are consistent with existing theoretical predictions for interaction corrections in optical properties of monolayer graphene.