Quantum capacitance

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

Mixed carbon nanotube bundle: Capacitance analysis and comparison with copper interconnect

Abstract: With technology scaling, copper (Cu) interconnect dimensions begin to come into the range of mean free path of electron typically 40nm. This results in surface and grain boundary scattering. Owing to these scattering phenomena resistivity of Cu begins to increase. This drives us to look for new materials for future very large scale integration (VLSI) interconnects. Mixed carbon nanotube (CNT) bundle has superior properties like current carrying capacity and conductivity compared to Cu interconnect. It is the mixture of single wall carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs). This is due to the nature of the bottom-up fabrication process. This paper presents capacitive analysis for mixed CNT bundle with respect to various process parameters viz. average diameter, inner to outer diameter ratio and probability of metallic tubes of bundle at 32nm technology node. The optimum values of these parameters provide minimum bundle capacitance. Results show that capacitance of the bundle is smaller compared to that of Cu for intermediate and global interconnect levels. It is also found that with technology scaling from 45nm to 22nm, bundle capacitance increases which is unlike the case of Cu interconnect. Furthermore, the bundle capacitance remains smaller than copper counterpart at these Nano-regime technologies.

Corrections to the capacitance between two electrodes due to the presence of quantum confined system

Abstract: We have studied the capacitance between two parallel plates enclosing a quantum confined system and its dependence on the applied voltage. The concepts of capacitance and differential capacitance are discussed together with their applicability to systems characterized by single.electron tunneling. We determine the tunneling thresholds by means of a formalism based on the minimization of the system free energy and we retrieve, as a special case, Luryi's quantum capacitance formula. We apply our method to the study of an idealized system made up of a number of quantum dots with random size distributed according to a gaussian. Results are shown for different choices of the position of the dots between the plates and of the voltage span applied to perform the measurement of the differential capacitance.

Theory of substrate, Zeeman, and electron-phonon interaction effects on the quantum capacitance in graphene

Abstract: Since the discovery of graphene, a lot of interest has been attracted by the zeroth Landau level, which has no analog in the conventional two dimensional electron gas. Recently, lifting of the spin and valley degeneracies has been confirmed experimentally by capacitance measurements, while in transport experiments, this is difficult due to the scattering in the device. In this context, we model interaction effects on the quantum capacitance of graphene in the presence of a perpendicular magnetic field, finding good agreement with experiments. We demonstrate that the valley degeneracy is lifted by the substrate and by Kekule distortion, whereas the spin degeneracy is lifted by Zeeman interaction. The two cases can be distinguished by capacitance measurements.

Multilayer graphene nanoribbon for 3D stacking of the transistor channel

Abstract: The graphene nanoribbon (GNR) transistor suffers from the problem of a low on-current due to the nanometer-wide channel. In this work, a self-consistent atomistic simulation is performed to explore the possibility of boosting the ballistic on-current of the GNRFET by using the experimentally accessible multilayer GNR, which provides a natural structure for 3D stacking of the transistor channel. The effects of the number of graphene layers and interlayer coupling strength are studied under different gating technologies. Only limited improvement of the on-current can be achieved with a typical bottom gate because of the small gate insulator capacitance. With a high-к gate, the improvement of the multilayer channel, however, is significant. Reducing the interlayer coupling can further increase the on-current by a factor of 2 for a 5-layer GNR channel.

First steps towards a quantum capacitance standard at METAS

Abstract: In the 5th framework program of the European Commission, several Metrology Institutes have teamed up in a project (COUNT) aimed at the realization of a primary standard of capacitance based on single electron resistive pumps. In this paper, we report the first steps towards the realization of such a quantum capacitance standard at METAS. The measurement setup is described and the stability diagram of the electron pump, measured at an electronic temperature of 160 mK, is shown. These preliminary results are promising for the future of the experiment.