Quantum capacitance

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

Compact modeling and design optimization of carbon nanotube field-effect transistors for the sub-10-nm technology nodes

Abstract: Single-wall semiconducting carbon nanotube (CNT) field-effect transistors (CNFETs) have been among the foremost candidates to complement Si and extend CMOS technology scaling to sub-10-nm technology thanks to the atomically thin body of CNTs and their near-ballistic transport [1–3]. However, non-idealities such as high contact resistance (R c ) [4], parasitic capacitance and tunneling leakage current can diminish the superior intrinsic electrical properties of CNTs in a highly scaled CNFET. Here we present the first data-calibrated compact model for CNFETs which captures dimensional scaling effects, metal-CNT contact resistance, parasitic capacitance, and direct source-to-drain tunneling leakage current. We then use this model to study design trade-offs and identify the remaining critical challenges for the CNFET technology. The model has been implemented in Verilog-A, is now available online [5], and will be described here for the first time.

Phase Shift Induced by Gate-Controlled Quantum Capacitance in Graphene FET

Abstract: The gate-controlled quantum capacitance and the channel resistance play an important role in the performance of graphene field-effect transistors (GFETs). This paper experimentally verifies that the output phase of the graphene field-effect transistor changes under the influence of quantum capacitance and the channel resistance, which are controlled by the gate voltage. This phenomenon is theoretically analyzed, and a model is established to simulate the phase shift. The obtained simulation results of the model are in good agreement with the experimental results. This work reveals the influence of gate voltage variation on the phase characteristics of GFETs and provides a research basis for the application of GFETs in phase shifter and the establishment of the small-signal model.

Spin-accumulation capacitance and its application to magnetoimpedance

Abstract: It has been known that spin-dependent capacitances usually coexist with geometric capacitances in a magnetic multilayer. However, the charge and energy storage of the capacitance due to spin accumulation has not been fully understood. Here, we resolve this problem starting from the charge storage in the spin degree of freedom: spin accumulation manifests itself as an excess of electrons in one spin channel and an equal deficiency in the other under the quasi-neutrality condition. This enables us to model the two spin channels as the two plates of a capacitor. Taking a ferromagnet/nonmagnet junction as an example and using a method similar to that for treating quantum capacitance, we find that a spin-accumulation (SA) capacitance can be introduced for each layer to measure its ability to store spins. A spatial charge storage is not essential for the SA capacitor and the energy stored in it is the splitting energy of the spin-dependent chemical potentials instead of the electrostatic energy. The SA capacitance is essentially a quantum capacitance due to spin accumulation on the scale of the spin-diffusion length. The SA capacitances can be used to reinterpret the imaginary part of the low-frequency magnetoimpedance.

Apparatus and a method

Abstract: An apparatus including a first electrode; a second electrode including graphene; and a dielectric between the first electrode and the second electrode; input circuitry configured to change a charge state of the dielectric by causing electric charges to be trapped in the dielectric; and output circuitry configured to detect a value dependent upon a quantum capacitance of the graphene of the second electrode, wherein the quantum capacitance of the graphene is dependent upon the charge state of the dielectric.