Interaction with electron donor and acceptor molecules such as aniline and nitrobenzene brings about marked changes in the Raman spectrum and the electronic structure of graphene, prepared by the exfoliation of graphitic oxide.

Changes in the electronic structure and properties of graphene induced by molecular charge-transfer

Two-dimensional graphene monolayers and bilayers exhibit fascinating electrical transport behaviors. Using infrared spectroscopy, we find that they also have strong interband transitions and that their optical transitions can be substantially modified through electrical gating, much like electrical transport in field-effect transistors. This gate dependence of interband transitions adds a valuable dimension for optically probing graphene band structure. For a graphene monolayer, it yields directly the linear band dispersion of Dirac fermions, whereas in a bilayer, it reveals a dominating van Hove singularity arising from interlayer coupling. The strong and layer-dependent optical transitions of graphene and the tunability by simple electrical gating hold promise for new applications in infrared optics and optoelectronics.

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Gate-Variable Optical Transitions in Graphene

In this paper, new sensors based on a double-gate (DG) graphene nanoribbon field-effect transistor (GNRFET), for high-performance DNA and gas detection, are proposed through a simulation-based study. The proposed sensors are simulated by solving the Schrodinger equation using the mode space non-equilibrium Green’s function formalism coupled self-consistently with a 2D Poisson equation under the ballistic limits. The dielectric and work function modulation techniques are used for the electrical detection of DNA and gas molecules, respectively. The behaviors of both the sensors have been investigated, and the impacts of variation in geometrical and electrical parameters on the sensitivity of sensors have also been studied. In comparison to other FET-based sensors, the proposed sensors provide not only higher sensitivity but also better electrical and scaling performances. The obtained results make the proposed DG-GNRFET-based sensors as promising candidates for ultra-sensitive, small-size, low-power and reliable CMOS-based DNA, and gas sensors.

Double-Gate Graphene Nanoribbon Field-Effect Transistor for DNA and Gas Sensing Applications: Simulation Study and Sensitivity Analysis

Spectral beam splitting (SBS) hybrid PV/T system was a promising path for utilizing the full spectrum solar energy to cogenerate electricity and high-grade heat, with high conversion efficiency To settle the balance between photoelectric and photothermal conversion performance for full spectrum solar energy utilization, the sunlight based on wavelength matching was divided into two or more parts at band-gap wavelength by a spectral beam splitter: sunlight with wavelength at and close to the band-gap of PV cell was directed to generate electricity, while the sunlight with rest wavelength was used for thermal output SBS hybrid PV/T system can not only increase the overall efficiency, but can also decouple the photoelectric and photothermal conversion process in separated operation temperatures The current state-of the-art review on the advancements of SBS hybrid PV/T system performed with the aid of nanofluids, nano-film and semitransparent PV cells was presented in this work, with emphasis on the latest developments during the last decade Mechanisms of different SBS techniques, progress in system, thermodynamic and cost analyses of nanofluids, nano-film and semitransparent PV cell based SBS hybrid PV/T system were discussed in detail to give a comprehensive understanding of the nature of the full spectrum solar energy utilization and the factors impacting on the system efficiency Though the cost increase can be offset by extra energy efficiency gain, the wavelength matching, optical losses and stability of SBS hybrid PV/T system needs to be solved for future industrial application

Progress in full spectrum solar energy utilization by spectral beam splitting hybrid PV/T system

A leaf-inspired photon management scheme using optically tuned bilayer nanoparticles for ultra-thin and highly efficient photovoltaic devices

For the first time, a new type of carbon nanotube field-effect transistor (CNTFET), the dual material gate (DMG)-CNTFET, is proposed and simulated using quantum simulation that is based on self-consistent solution between two-dimensional Poisson equation and Schrodinger equation with open boundary conditions, within the nonequilibrium Green's function (NEGF) framework. The proposed structure is similar to that of the conventional coaxial CNTFET with the exception that the gate of the DMG-CNTFET consists of two laterally contacting metals with different work functions. Simulation results show DMG-CNTFET significantly decreases leakage current, drain conductance and subthreshold swing, and increases on–off current ratio and voltage gain as compared to conventional CNTFET. We demonstrate that the potential in the channel region exhibits a step function that ensures the screening of the drain potential variation by the gate near the drain resulting in suppressed short-channel effects like the drain-induced barrier lowering (DIBL) and hot-carrier effect.

Detailed simulation study of a dual material gate carbon nanotube field-effect transistor

For the first time, the potential impact of high- κ gate dielectrics on carbon nanotube field-effect transistors (CNTFETs) is studied over a wide range of dielectric permittivities using a two-dimensional model. It is found that the high- κ CNTFETs afford high ON currents and subthreshold swings near its theoretical limit. Likewise average electron velocity at the top of the barrier increases. Key transistor performance parameters, transconductance and carrier mobility improve for high- κ CNTFETs.

Investigation of the novel attributes of a carbon nanotube FET with high-κ gate dielectrics

In this paper, we present the unique features exhibited by a proposed structure of coaxially gated carbon nanotube field-effect transistor (CNTFET) with doped source and drain extensions using the self-consistent and atomistic scale simulations, within the nonequilibrium Green's function formalism. In this novel CNTFET structure, three adjacent metal cylindrical gates are used, where two side metal gates with lower workfunction than the main gate as an extension of the source/drain on either side of the main metal gate are biased, independent of the main gate, to create virtual extensions to the source and the drain and also to provide an effective electrical screen for the channel region from the drain voltage variations. We demonstrate that the proposed structure of CNTFET shows improvement in device performance focusing on leakage current, on-off current ratio, and voltage gain. In addition, the investigation of short-channel effects for the proposed structure shows improved drain-induced barrier lowering, hot-carrier effect, and subthreshold swing, all of which can affect the reliability of CMOS devices.

Zahra Arefinia

Papers

Detailed simulation study of a dual material gate carbon nanotube field-effect transistor

Investigation of the novel attributes of a carbon nanotube FET with high-κ gate dielectrics

Quantum Simulation Study of a New Carbon Nanotube Field-Effect Transistor With Electrically Induced Source/Drain Extension

Optical and electrical modeling of solar cells based on graphene/Si nanowires with radial p–i–n junctions

Design of InP-based truncated nanopyramid solar cells with conformal coating of PEDOT: PSS for improved light harvesting efficiency