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Quantum capacitance
About: Quantum capacitance is a research topic. Over the lifetime, 954 publications have been published within this topic receiving 24165 citations.
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TL;DR: In this article, the gate leakage current in a graphene field effect transistor (FET) was investigated and it was shown that a higher oxide electric field results in larger Fowler-Nordheim tunneling current than that in a silicon FET.
Abstract: The unique band structure of graphene makes the gate leakage current in a graphene field-effect transistor (FET) different from that in silicon FET. Theoretical investigation in this letter demonstrates that the Fowler-Nordheim tunneling current (TC) in a graphene FET is different from that in a silicon FET. Numerical calculations show that a higher oxide electric field results in larger TC in a graphene FET than that in a silicon FET. This implies that, to ensure a workable graphene FET, a thicker gate oxide is needed to limit the gate leakage current compared to that for a silicon FET.
22 citations
TL;DR: In this paper, the conversion efficiency of field effect transistors with even-odd symmetry is elucidated, and it is shown that even symmetry, due to electronhole symmetry in graphene, affords efficient even-harmonic multiplication.
Abstract: The conversion efficiency of field-effect transistors with even-odd symmetry is elucidated in this work. From symmetry considerations, this work reveals that even symmetry, due to electron-hole symmetry in graphene, affords efficient even-harmonic multiplication. Odd symmetry, associated with linear charge transport, affords suppression of odd-harmonic signals. For the ideal symmetric transistor multiplier, conversion efficiency with relatively large power gain is achievable, while for practical graphene transistors, the efficiency can be substantially less than unity due to non-idealities such as contact resistance, high impurity densities, and low gate capacitance. In the quantum capacitance limit of graphene transistor, near-lossless conversion efficiency is available.
22 citations
TL;DR: In this article, the authors specify a powerful way to boost quantum capacitance of graphene-based electrode materials by density functional theory calculations, and perform functionalization of graphene to manifest high-quantum capacitance.
Abstract: In this paper, we specify a powerful way to boost quantum capacitance of graphene-based electrode materials by density functional theory calculations. We performed functionalization of graphene to manifest high-quantum capacitance. A marked quantum capacitance of above $$420\,\upmu \mathrm{F}\,\mathrm{cm}^{-2}$$ has been observed. Our calculations show that quantum capacitance of graphene enhances with nitrogen concentration. We have also scrutinized effect on the increase of graphene quantum capacitance due to the variation of doping concentration, configuration change as well as co-doping with nitrogen and oxygen ad-atoms in pristine graphene sheets. A significant increase in quantum capacitance was theoretically detected in functionalized graphene, mainly because of the generation of new electronic states near the Dirac point and the shift of Fermi level caused by ad-atom adsorption.
22 citations
TL;DR: In this manuscript, the effect on the quantum capacitance of noncovalent basal plane functionalization using 1-pyrenebutanoic acid succimidyl ester and glucose oxidase is reported and it is found that functionalized samples tested in air have increased maximum capacitance compared to vacuum but similar to air, and quantum capacitor "tuning" that is greater than that in vacuum and ambient atmosphere.
Abstract: The concentration-dependent density of states in graphene allows the capacitance in metal–oxide–graphene structures to be tunable with the carrier concentration. This feature allows graphene to act as a variable capacitor (varactor) that can be utilized for wireless sensing applications. Surface functionalization can be used to make graphene sensitive to a particular species. In this manuscript, the effect on the quantum capacitance of noncovalent basal plane functionalization using 1-pyrenebutanoic acid succimidyl ester and glucose oxidase is reported. It is found that functionalized samples tested in air have (1) a Dirac point similar to vacuum conditions, (2) increased maximum capacitance compared to vacuum but similar to air, (3) and quantum capacitance “tuning” that is greater than that in vacuum and ambient atmosphere. These trends are attributed to reduced surface doping and random potential fluctuations as a result of the surface functionalization due to the displacement of H2O on the graphene sur...
22 citations
TL;DR: In this paper, a 10-stack quantum barrier varactor (MSQBV) with lattice-matched InGaAs/InAlAs/INGaAs barriers on InP was proposed.
Abstract: Conventional multi-stack quantum barrier varactor (MSQBV) diodes on GaAs suffer from leaky barriers and low breakdown voltage, which limits their performance in high-power applications. Using a lattice-matched InGaAs/InAlAs/InGaAs barriers on InP we have grown a new 10-stack device. Measurement results are presented that demonstrate low series resistance, large capacitance modulation, and significantly higher breakdown voltage than previously reported devices. The power capability of this new device has been investigated by simulations and measurements. An experiment in a waveguide tripler circuit shows a 19.6 dBm output power at 93 GHz. This is the highest output power reported from a single QBV device at W-band. >
22 citations