Quantum capacitance

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

Realization of the Farad From the AC Quantum Hall Resistance at PTB—14 Years of Experience

Abstract: Since 2008, the capacitance unit, the farad, has been realized at the Physikalisch-Technische Bundesanstalt (PTB) successfully and routinely using a measurement chain starting at two quantum Hall resistance (QHR) devices operated at ac. After the first years of practice, a systematic scatter became apparent which indicated an increased measurement uncertainty. This was not due to systematic errors in bridge circuitries (which were fixed in 2014) but accidental incidents. Since then, valuable operational experience has been gained on how to avoid them. As a result, the current uncertainty of the calibration of a 10-pF capacitance standard is back to the initially published relative uncertainty of $6\times 10^{-9}$ ( $k = 1$ ), which is still unmatched. In this article, we report the findings from the operational experience gained during this time, in particular the effect of charge carriers trapped in a QHR device due to accidental discharging incidents. Besides helping practitioners to avoid the pitfalls, the low uncertainty provides a basis for improving the capacitance standards and for reducing the calibration period. Furthermore, we present a new and unique digital sinewave generator. Finally, we show that precision ac measurements of gallium arsenide (GaAs)-based QHRs do not require a ³He cryo-magnet system but can be carried out in a cheaper and easier-to-operate ⁴He cryo-magnet system at 2.1 K.

Unconventional photo capacitor with giant light induced capacitance enhancement

Abstract: This chapter explains a new concept for photodetection through management of internal energies in a two-dimensional charge system (2DCS). The exchange and correlation energy terms, that are associated to quantum mechanical many body interactions of a 2DCS, are manipulated through light generated carriers. This is then manifested as a giant enhancement in capacitance of a metal-semiconductor-metal (MSM) variable capacitor with an embedded 2DCS. This feature is controllable by incident light intensity, making the MSM-2DCS device suitable for non-transport based photodetection.

In-depth Analysis of Characteristics for an Edge Disordered Sub-10 nm Armchair Graphene Nanoribbon Field Effect Transistor

Abstract: Graphene nanoribbon is a probable alternative in observing transistor behavior due to its semiconducting properties. One of the fruitful investigations in transistor research is I-V characteristics by using proper bias voltage, in presence of capacitance. In this paper, we will observe the I-V characteristics of Armchair Graphene Nanoribbon (AGNR) by considering the quantum as well as the classical capacitance for two different sizes of AGNR which are 5.04nm and 10.20nm. These two cases will eventually help us concluding a valuable decision in sub-10 nm range based device analysis.

On the effect of quantum capacitance in graphene FET THz detectors

Abstract: We analyze the impact of quantum capacitance on the response of graphene-based field effect transistors operating as THz detectors. Resulting from its atomically thin body and its particular band structure, quantum capacitance in graphene has a different behavior than that in bulk-semiconductor two-dimensional electron gases. Furthermore, we analyze and identify non-homogeneities and impurities, which in practice lead to a finite minimum effective charge density as well as to a finite minimum conductivity, as an effect that can degrade the predicted theoretical performance of graphene-based THz devices.

Effect of Channel Dimensions on Transfer Characteristics of Graphene FET

Abstract: Graphene-based field-effect transistors (FETs)have received widespread attention as an alternative for conventional silicon devices. The purpose of this paper is to present a new simulation scheme for the I-V characteristics of graphene based FETs. Using the same, we studied the channel length and width dependence behaviour of the transfer characteristics of graphene based FETs (GFETs)with various channel lengths from 0.75 μm to 1.25 μm and widths from 1.75 μm to 2.25 μm, From our study, we observed that, the Dirac point is independent of the channel length and width for the range of values considered. However, the magnitude of the current progressively increases with increase in width of the channel.