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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: It is shown here that exposure of BLFO surfaces to UV light induces a counterintuitive shift of the O2p valence state to lower binding energy of up to 243 meV which is a direct signature of negative electronic compressibility (NEC).
Abstract: Light-sensitive capacitance variation of Bi0.95La0.05FeO3 (BLFO) ceramics has been studied under violet to UV irradiation. The reversible capacitance enhancement up to 21% under 405 nm violet laser irradiation has been observed, suggesting a possible degree of freedom to dynamically control this in high dielectric materials for light-sensitive capacitance applications. By using ultraviolet photoemission spectroscopy (UPS), we show here that exposure of BLFO surfaces to UV light induces a counterintuitive shift of the O2p valence state to lower binding energy of up to 243 meV which is a direct signature of negative electronic compressibility (NEC). A decrease of BLFO electrical resistance agrees strongly with the UPS data suggesting the creation of a thin conductive layer on its insulating bulk under light irradiation. By exploiting the quantum capacitance model, we find that the negative quantum capacitance due to this NEC effect plays an important role in this capacitance enhancement.
6 citations
TL;DR: In this article, a detailed computational model was proposed to demonstrate that the photoconductivity arises from the electrostatic doping of graphene, induced by the surface accumulation of photogenerated carriers at the graphene/substrate interface.
Abstract: A single atomic layer of graphene, integrated onto an undoped bulk substrate in a back-gated transistor configuration, demonstrates surprising strong photoconduction, and yet, the physical origin of the photoresponse is not fully understood. Here, we use a detailed computational model to demonstrate that the photoconductivity arises from the electrostatic doping of graphene, induced by the surface accumulation of photogenerated carriers at the graphene/substrate interface. The accumulated charge density depends strongly on the rate of charge transfer between the substrate and the graphene; the suppression of the transfer rate below that of carrier’s thermal velocity is an essential prerequisite for a substantial photoinduced doping in the graphene channel under this mechanism. The contact-to-graphene coupling (defined by the ratio of graphene–metal contact capacitance to graphene’s quantum capacitance) determines the magnitude of photoinduced doping in graphene at the source/drain contacts. High-performance graphene phototransistors would, therefore, require careful engineering of the graphene–substrate interface and optimization of graphene–metal contacts.
6 citations
TL;DR: In this paper, semi-analytical models for the calculation of the quantum capacitance of both monolayer and bilayer graphene and its nanoribbons, are presented, taking into account both the edge bond relaxation and third-nearest-neighbour interaction in the band structure of GNRs.
Abstract: In this chapter, semi-analytical models for the calculation of the quantum capacitance of both monolayer and bilayer graphene and its nanoribbons, are presented. Since electron-hole puddles are experimental facts in all graphene samples, they have been incorporated in our calculations. The temperature dependence of the quantum capacitance around the charge neutrality point is also investigated and the obtained results are in agreement with many features recently observed in quantum capacitance measurements on both monolayer and bilayer graphene devices. Furtheremore, the impact of finite-size and edge effects on the quantum capacitance of graphene nanoribbons is studied taking into account both the edge bond relaxation and third-nearest-neighbour interaction in the band structure of GNRs.
6 citations
TL;DR: In this article, the authors derived a Boltzman-like equation for the partial WDF describing both propagating and non-propagating electron modes in an effective potential generated by the adiabatic QPC.
Abstract: We have calculated the admittance of a two-dimensional quantum point contact (QPC) using a novel variant of the Wigner distribution function (WDF) formalism. In the semiclassical approximation, a Boltzman-like equation is derived for the partial WDF describing both propagating and nonpropagating electron modes in an effective potential generated by the adiabatic QPC. We show that this quantum kinetic approach leads to the well-known stepwise behavior of the real part of the admittance (the conductance), and of the imaginary part of the admittance (the emittance), in agreement with the latest results, which is determined by the number of propagating electron modes. It is shown, that the emittance is sensitive to the geometry of the QPC, and can be controlled by the gate voltage. We established that the emittance has contributions corresponding to both quantum inductance and quantum capacitance. Stepwise oscillations in the quantum inductance are determined by the harmonic mean of the velocities for the propagating modes, whereas the quantum capacitance is a significant mesoscopic manifestation of the non-propagating (reflecting) modes.
6 citations
30 Dec 2016
TL;DR: In this article, a dual-gate field effect transistor based on monolayer graphene with the use of a combined model is considered, where the following important factors such as quantum capacitance, hole and electron mobility difference, drain and source resistances are taken into account.
Abstract: Graphene is a nanomaterial that due to unique properties has attracted great interest for various applications, in particular, for development of nanoelectronic devices. In the paper the graphene field-effect transistors (GFET) and resonant tunneling diodes (RTD) are analyzed with the use of proposed models. First, simulation of dual-gate field-effect transistor based on monolayer graphene with the use of proposed combined model is considered. In the model the following important factors such as quantum capacitance, hole and electron mobility difference, drain and source resistances are taken into account. Investigations of dependence of a drain current on drain voltage for various top-gate-to-source voltages are performed. Influence of channel length, source and drain resistances on output characteristics of the device is analyzed. Comparison of calculation results with simulation ones obtained with the known models was carried out. Secondly, simulation of graphene-based nanostructures on hexagonal boron nitride, silicon carbide and silicon dioxide substrates was performed using proposed self-consistent numerical model, based on effective wave function formalism. The developed models in detail were described in our previous works. The possibility of using a proposed self-consistent model for double- and triple-barrier graphene-based RTD simulation was illustrated. As well as it was investigated the influence of different parameters on IV-characteristics of graphene-based RTDs. It was shown that it is necessary to take into account extended (passive) regions for adequate simulation of these devices.
5 citations