Quantum capacitance

About: Quantum capacitance is a research topic. Over the lifetime, 954 publications have been published within this topic receiving 24165 citations.

A Comparative Study of Ballistic Transport Models for Nanowire MOSFETs

Abstract: We comparatively study two representative ballistic transport models of nanowire metal-oxide-semiconductor field effect transistors, i.e. the Natori model and the Jimenez model. The limitations and applicability of both the models are discussed. Then the Jimenez model is extended to include atomic dispersion relations and is compared with the Natori model from the aspects of ballistic current and quantum capacitance. It is found that the Jimenez model can produce similar results compared with the more complex Natori model even at very small nanowire dimensions.

Acetone sensing using graphene quantum capacitance varactors

Abstract: Sensing of acetone using the quantum capacitance in graphene is demonstrated. The sensor was constructed by using graphene as the top electrode in a metal-oxide-graphene variable capacitor (varactor) structure. The relative capacitance change was found to vary with acetone concentration with a relative capacitance sensitivity, ΔC/C of 1.29 ± 0.04 × 10−4 % / ppmv. The sensor was also found to have 3∗ enhanced sensitivity in dry air compared to N 2 and showed excellent reversibility. The results represent the first step toward the realization of passive, wireless acetone sensors using graphene varactors.

Resonant plasmonic terahertz detection in vertical graphene-base hot-electron transistors

Abstract: We analyze dynamic properties of vertical graphene-base hot-electron transistors (GB-HETs) and consider their operation as detectors of terahertz (THz) radiation using the developed device model. The GB-HET model accounts for the tunneling electron injection from the emitter, electron propagation across the barrier layers with the partial capture into the GB, and the self-consistent oscillations of the electric potential and the hole density in the GB (plasma oscillations), as well as the quantum capacitance and the electron transit-time effects. Using the proposed device model, we calculate the responsivity of GB-HETs operating as THz detectors as a function of the signal frequency, applied bias voltages, and the structural parameters. The inclusion of the plasmonic effect leads to the possibility of the HET-GBT operation at the frequencies significantly exceeding those limited by the characteristic RC-time. It is found that the responsivity of GB-HETs with a sufficiently perfect GB exhibits sharp resonant maxima in the THz range of frequencies associated with the excitation of plasma oscillations. The positions of these maxima are controlled by the applied bias voltages. The GB-HETs can compete with and even surpass other plasmonic THz detectors.

A Computational Study on the Performance of Graphene Nanoribbon Field Effect Transistor

Abstract: Despite the simplicity of the hexagonal graphene structure formed by carbon atoms, the electronic behavior shows fascinating properties, giving high expectation for the possible applications of graphene in the field The Graphene Nano-Ribbon Field Effect Transistor (GNRFET) is an emerging technology that received much attention in recent years In this paper, we investigate the device performance of Graphene Nanoribbon Field Effect Transistor (GNRFET) as a function of contact doping concentration and the gate insulator dielectric constant The simulations are based on the Non-Equilibrium Green’s function (NEGF) method coupled with a two dimensional Poisson equation in the ballistic regime We assume a tight-binding Hamiltonian in mode space representation By applying proper symmetric source and drain doping concentrations, It is observed that the GNRFET with low doping concentration has higher transconductance, lower Subthreshold Swing, lower Off-current (Ioff), and higher ratioof On-current to Off-current (Ion/Ioff) Moreover, The GNRFET with high doping concentration has smaller quantum capacitance, higher intrinsic cut-off frequency, and lower gate capacitance in comparison with low doping GNRFET As we know, Selection of a suitable gate dielectric constant is important in determining device performance The results indicate that the GNRFET with high dielectric constant has higher transconductance, lower Off-current, higher On-current and higher ratio of Ion/Ioff in comparison with low dielectric GNRFET Furthermore, the GNRFET with low dielectric constant has smaller capacitances in gate, drain and source The GNRFET with high dielectric constant has lower Sub-threshold Swing

Quantum capacitances of molecules, fullerenes and carbon nanotubes by the partitioned real-space density functional method

Abstract: Capacitances of molecules, fullerenes and carbon nanotubes under the condition of no electron-tunneling are calculated by the partitioned real-space density functional method that has been recently developed. We found that a quantum capacitance of a spherical jellium bielectrode decreases and approaches the classical value as the electron density increases. The capacitances of fullerenes and carbon nanotubes do not depend on the detailed atomic geometry but on the overall shapes. The values of the capacitances of these nanostructures are found to be a few 10-20 F and are compatible with the experimental ones determined by the scanning tunneling microscopy studies.