We investigate electronic transport in Josephson junctions formed by individual single-walled carbon nanotubes coupled to superconducting electrodes. We observe enhanced zero-bias conductance (up to 10e2/h) and pronounced sub-harmonic gap structures in differential conductance, which arise from the multiple Andreev reflections at superconductor/nanotube interfaces. The voltage-current characteristics of these junctions display abrupt switching from the supercurrent branch to the resistive branch, with a gate-tunable switching current ranging from 65 pA to 2.5 nA. The finite resistance observed on the supercurrent branch and the magnitude of the switching current are in good agreement with the classical phase diffusion model for resistively and capacitively shunted junctions. 相似文献
Suspended single-walled carbon nanotube devices comprised of high-quality electrical contacts and two electrostatic gates per device have been prepared. Compared to nanotubes pinned on substrates, the suspended devices exhibit little hysteresis related to environmental factors and act as cleaner Fabry-Perot interferometers or single-electron transistors. The high-field saturation currents in the suspended nanotubes related to optical phonon or zone-boundary phonon scattering are significantly lower due to the lack of efficient heat sinking. The multiple-gate design may also facilitate future investigations into the electromechanical properties of nanotube quantum systems. 相似文献
Materials with an ultralow density and ultrahigh electromagnetic‐interference (EMI)‐shielding performance are highly desirable in fields of aerospace, portable electronics, and so on. Theoretical work predicts that 3D carbon nanotube (CNT)/graphene hybrids are one of the most promising lightweight EMI shielding materials, owing to their unique nanostructures and extraordinary electronic properties. Herein, for the first time, a lightweight, flexible, and conductive CNT–multilayered graphene edge plane (MLGEP) core–shell hybrid foam is fabricated using chemical vapor deposition. MLGEPs are seamlessly grown on the CNTs, and the hybrid foam exhibits excellent EMI shielding effectiveness which exceeds 38.4 or 47.5 dB in X‐band at 1.6 mm, while the density is merely 0.0058 or 0.0089 g cm?3, respectively, which far surpasses the best values of reported carbon‐based composite materials. The grafted MLGEPs on CNTs can obviously enhance the penetration losses of microwaves in foams, leading to a greatly improved EMI shielding performance. In addition, the CNT–MLGEP hybrids also exhibit a great potential as nano‐reinforcements for fabricating high‐strength polymer‐based composites. The results provide an alternative approach to fully explore the potentials of CNT and graphene, for developing advanced multifunctional materials. 相似文献
Two-dimensional graphene, carbon nanotubes, and graphene nanoribbons represent a novel class of low dimensional materials
that could serve as building blocks for future carbon-based nanoelectronics. Although these systems share a similar underlying
electronic structure, whose exact details depend on confinement effects, crucial differences emerge when disorder comes into
play. In this review, we consider the transport properties of these materials, with particular emphasis on the case of graphene
nanoribbons. After summarizing the electronic and transport properties of defect-free systems, we focus on the effects of
a model disorder potential (Anderson-type), and illustrate how transport properties are sensitive to the underlying symmetry.
We provide analytical expressions for the elastic mean free path of carbon nanotubes and graphene nanoribbons, and discuss
the onset of weak and strong localization regimes, which are genuinely dependent on the transport dimensionality. We also
consider the effects of edge disorder and roughness for graphene nanoribbons in relation to their armchair or zigzag orientation.
This article is published with open access at Springerlink.com 相似文献
The charge transport through ferrocene 1,1′‐diamine (FDA) molecules between gold electrodes is investigated using the mechanically controllable break junction technique combined with a theoretical framework of density functional theory simulations to understand the physics of these molecular junctions. The characteristic conductances of the molecule are measured at low bias as well as current–voltage (IV) characteristics. By fitting the IV characteristics to the single‐level model, the values for the position of the molecular level, mainly responsible for the transport, and its coupling to the leads, are obtained. The influence of the binding sites, molecular conformation, and electrode distance are systematically studied from a theoretical perspective. While a strong dependence of conductance on the adsorption geometry is found, the decrease of conductance as a function of electrode distance arises mainly from a decrease of coupling strength of the molecular electronic orbitals through a reduced overlap and, to a lesser extent, from a shift of their alignment with respect to the Fermi energy. 相似文献
For the miniaturization of microelectronics, carbon nanotubes (CNTs) are regarded as ideal candidates for the next generation of nanoelectronics because of their excellent properties. To realize CNT‐based electronics, intramolecular junctions are required components, which can not only connect different CNTs for integration, but can also act as functional building blocks in the circuit, such as rectifiers, field‐effect transistors, switches, amplifiers, photoelectrical devices, etc. Therefore, intense attention has been focused on this topic and many advances have been achieved, especially in recent years. On the other hand, some challenges also exist. To provide researchers with a comprehensive overview of this field, this review discusses the synthesis, properties, and applications of intramolecular junctions of CNTs in detail. Among them, the applications of CNT integration are discussed specially. Furthermore, a brief summary and an outlook of future work are provided.
This article concerns the investigation of the vibrational behavior of double-walled carbon nanotubes/double-layered graphene sheets junctions using the finite element method. The bonds and atoms are modeled by beam and mass elements, respectively. Moreover, the van der Waals interactions are simulated by spring elements. The effects of the length of the nanotube and the dimensions of the nanosheet on the natural frequencies of the junctions are examined. It is shown that when the boundary conditions are applied on the nanotube, the geometrical parameters of nanotubes have a significant effect on the vibrational behavior of the junctions. 相似文献
A systematic analysis of electron transport characteristics for 1D heterojunctions with two nitrogen‐doped (N‐doped) capped carbon nanotubes (CNTs) facing one another at different conformations is presented considering the chirality of CNTs (armchair(5,5) and zigzag(9,0)) and spatial arrangement of N‐dopants. The results show that the modification of the molecular orbitals by the N‐dopants generates a conducting channel in the designed CNT junctions, inducing a negative differential resistance (NDR) behavior, which is a characteristic feature of the Esaki‐like diode, that is, tunneling diode. The NDR behavior significantly depends on the N‐doping site and the facing conformations of the N‐doped capped CNT junctions. Furthermore, a clear interpretation is presented for the NDR behavior by a rigid shift model of the HOMO‐ and LUMO‐filtered energy levels in the left and right electrodes under the applied biases. These results give an insight into the design and implementation of various electronic logic functions based on CNTs for applications in the field of nanoelectronics. 相似文献
In this article, we report the synthesis of ultra-long carbon nanotubes (CNTs) by thermal chemical vapour deposition method. Ultra-long, individual and aligned CNTs were directly grown on a flat silicon substrate. The orientation of the nanotubes was found parallel to the gas flow direction. The ultra-long CNTs were grown with different transition metallic salts, such as nickel chloride, iron (III) chloride, cobalt acetate and ruthenium acetate, as the catalysts. The influence of the growth conditions, such as growth temperature, reactive gas flow on the length and alignment of the CNTs was studied in detail. By using different catalysts, ultra-long single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) were successfully grown. These ultra-long CNTs were transferred to other substrates by two methods. (1) The first method is to use polydimethylsiloxane as a stamp. (2) The second method is to use KOH as an etching agent. The diameter and length of the CNTs were characterised by transmission electron microscope, scanning electron microscope, atomic force microscope and Raman spectroscopy. The results indicate that the length of the CNTs can reach up to 4?mm. The diameter of the SWCNTs is in the range of 0.7–2.1?nm and the diameter of the MWCNTs is approximately 150?nm. 相似文献
Inspired by the traditional Chinese “pancake‐making” method, the efficient electromagnetic interferences (EMI) shielding composite carbon films are conveniently obtained by assembling graphene oxide (GO) sheets, carbon nanotubes (CNTs), and Co/C nanocomposites into a laminated “nacre‐like” structure. The developed composite carbon films are characterized by a shielding effectiveness (SE) up to ≈51 dB in X band with a small thickness of ≈34.3 µm. Moreover, the composite carbon film shows favorable flexibility and the SE values almost keep a constant after repeatedly bending test. These results demonstrate a promising approach to simply fabricate a flexible and highly efficient EMI shielding material. 相似文献
Mesoscopic fluctuations, manifesting the quantum interference (QI) of electrons, have been theoretically proposed in bilayer Coulomb drag systems. Unfortunately, these phenomena are usually observed at cryogenic temperatures, which severely limits their novel physics for pragmatic applications. In this paper, observation of room‐temperature QI and Coulomb drag in a multilayer WSe2 transistor is reported via graphene contacts separately at its top and bottom layers. The central layers of WSe2 act as an insulating region with a width of few nanometers, which spatially separates the top and bottom conducting channels and provides a strong Coulomb interaction between them, leading to large conductance oscillations at room temperature. The gradual suppression of the oscillations with the increase in the applied magnetic field and/or injected current further confirms the QI phenomenon. With the decrease in temperature, the Coulomb drag effect is exhibited in the system owing to the increased thickness of the insulating region. This study reveals a novel approach for realization of advanced quantum electronics operating at high temperatures. 相似文献
