Quantum capacitance

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

Quantum capacitance and compressibility of graphene: The role of Coulomb interactions

Abstract: Many-body effects on quantum capacitance, compressibility, renormalized Fermi velocity, and kinetic and interaction energies of massless Dirac electrons in graphene, induced by Coulomb interactions, are analyzed theoretically in the first-order, Hartree-Fock, and random-phase approximations. Recent experimental data on quantum capacitance and renormalized Fermi velocity are analyzed and compared with the theory. The bare Fermi velocity and the effective dielectric constants are obtained from the experimental data. A combined effect of Coulomb interactions and Gaussian fluctuations of the disorder potential is considered.

Edge chemistry engineering of graphene nanoribbon transistors: A computational study

Abstract: Using the density-functional theory (DFT) simulation and a top-of-the-barrier ballistic transport model, we present a simulation framework for assessing the performance limits of graphene nanoribbon (GNR) FETs with edges terminated by different chemical species. We find significant effects of edge chemistry on the quantum capacitance, carrier injection velocity, channel conductance and balance between the nFET and the pFET of GNRFETs. The H termination is identified to have the largest on current, carrier injection velocity, and the best balance between the nFET and the pFET with typical solid state gating technologies.

Wigner function description of a.c. transport through a two-dimensional quantum point contact

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 Boltzmann-like equation is derived for the partial WDF describing both propagating and non-propagating electron modes in an effective potential generated by the adiabatic QPC. We show that this quantum kinetic approach leads to the well known stepwise behaviour 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 derived by Christen and Buttiker, 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 have 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.

Anomalous Capacitance Enhancement Triggered by Light

Abstract: Capacitance of capacitors in which one or both plates are made of a two-dimensional charge system (2DCS) can be increased beyond their geometric structural value. This anomalous capacitance enhancement (CE) is a consequence of manipulation of quantum mechanical exchange and correlation energies in the ground state energy of the 2DCS. Macroscopically, it occurs at critical charge densities corresponding to transition from an interacting “metallic” to a noninteracting “insulator” mode in the 2-D system. Here, we apply this concept to a metal–semiconductor–metal capacitor with an embedded two-dimensional hole system (2DHS) underneath the plates for realization of a capacitance-based photodetector. Under sufficient illumination, and at critical voltages the device shows a giant CE of $ 200\%$ and a peak-to-valley ratio of over 4 at probe frequencies larger than 10 kHz. Remarkably, the light-to-dark capacitance ratio due to CE at this critical voltage is well over 40. Transition of the 2DHS from insulator to metallic, enforced by charge density manipulation due to light-generated carriers, accounts for this behavior, which may be used in optical sensing, photo capacitors, and photo transistors.