Nanotube Y-junctions Research Articles

On metric dimension of carbon nanotube Y-junctions

On metric dimension of carbon nanotube Y-junctions

On comparative analysis of graph entropies of symmetrical carbon nanotube Y-junctions

Entropy is crucial in statistical mechanics, thermodynamics, and information theory as it measures a system’s level of randomness or disorder. Entropy is widely used in mathematical chemistry and computational physics to predict the behavior of a system under various conditions. Among numerous carbon nanotube structures, three-terminal carbon nanotube junctions are important structures not only for electrical but also for mechanical appliances. Recently, significant attention has been given to the understanding of carbon nanotube junctions. This research paper focuses on calculating graph entropies based on Zagreb indices for symmetrical single-walled armchair carbon nanotube Y − junctions and comparing the index-entropies of these junctions. The study aims to demonstrate the behavior of the nanotube Y − junctions by adding atoms at the end of the tubes.

Topological indices and graph entropies for carbon nanotube Y-junctions

Topological indices and graph entropies for carbon nanotube Y-junctions

Sombor topological indices for different nanostructures

Euclidean geometry is utilized to establish the Sombor graph parameter and its invariants. It is sum of all adjacent vertices in graph theory dϒ2+dΓ2 where dϒ is the degree of the vertex ϒ. Geometrical interpretation is used to describe the new Sombor indices types. We examined, recently developed Sombor indices for various nanotube Y-junctions in this article. In specifically, the first area-based Sombor index was introduced by Euclidean geometry. Angular orientation concept to construct the second, fourth, and sixth Sombor graph parameters, while third and fifth Sombor graph parameters are constructed by perimeter.

In situ TEM synthesis of carbon nanotube Y-junctions by electromigration induced soldering

In this work, we utilize Joule heating to convert Pt-embedded amorphous carbon nanofiber (CNF) to multiwall carbon nanotube (CNT) in a transmission electron microscope (TEM). The transformation process of Pt-embedded amorphous CNF to multiwall CNT and nano-soldering process using Pt encapsulated CNT was investigated in TEM in detail. Molten Pt-encapsulated inside CNF and CNT always flowed towards the anode, proving electromigration to be the dominant force over thermal migration. Controllable electromigration of Pt was utilized to connect the Pt-included CNT to another CNT, thus forming a seamlessly welded CNT structure. Further, two separate CNF were brought together to form Y-contact which was transformed into Y-junction CNT structure by controlled electromigration of Pt. Changes in morphology and electrical property during CNT formation and nano-soldering were probed in real time with high resolution TEM. Our method provides a procedure for the position control synthesis of CNT and its nano-soldering which can be an important step for future development of a CNT based nanoelectrical circuit.

Planar trivalent polygonal networks constructed from carbon nanotube Y-junctions

This work is the first step towards proving that general planar polygonal networks can be constructed as patterns of carbon nanotubes. A subset of the planar polygonal networks, namely the trivalent planar networks, are studied. These patterns can be constructed from carbon nanotubes such that every intersection point of the networks is replaced with a carbon nanotube Y-junction. Accordingly the basic task is to show the basic connections of the carbon nanotube Y-junctions. The basic set of connected Y-junctions is defined and models of the structures are shown. Nanorings with two, three or more branches are constructed from two, three or more Y-junctions such that two tubes of every Y-junction are joined to the neighbouring tubes with the third tube being free. Because of the known, exceptional electronic behaviour of carbon nanotubes, combinations of basic elements of planar nanotube networks could motivate new experimental and theoretical works having the goal of finding the basic electronic tools for nanocircuits.

Size effect of quantum conductance in carbon nanotube Y-Junctions

This paper studies the quantum conductance properties of three-terminated carbon nanotube Y-junctions, which are built by connecting three (5,5) single-walled carbon nanotubes. The results show that the quantum conductance at the Fermi energy oscillates periodically with the junction's size, and the number of oscillating periodic layers is 3 which is the same as that in the two terminated (10,0)/m(5, 5)/(10,0) junctions. Moreover, this Y-junction with different size exhibits an obviously different distribution of electron current in the two drain branches, called shunt valve effect of electronic current. Thus the degree of this effect can be controlled and modulated directly by constructing the three branches' sizes or the distribution of defect. The results show in detail that the difference between the two drain currents can be up to two times for some constructions with special sizes. In addition, the uniform distribution of defects in the Y-junction leads to lower quantum conductance than that of other defect configurations.

Continuum modeling of carbon nanotube-based super-structures

Abstract The recently discovered carbon nanotube-based super-nanotubes (SNTs), super-graphene (SG) and super-square (SS) are modeled using the equivalent beam concept (EBC). By substituting carbon nanotubes with elastic beams of identical mechanical behavior, the atomic lattice is simulated with the classical strut-based lattice, thus enabling continuum modeling using finite elements. Young’s modulus, failure stress and strain of the SNTs are derived and compared against results from molecular–structural mechanics and molecular dynamics methods found in the literature. In general, a good agreement is achieved; occurred deviation is mainly due to the behavior of the nanotube Y-junctions which are omitted by the EBC. Parametric studies conducted reveal an appreciable influence of the SNT radius and chirality on the mechanical properties of the SNTs. In-plane elastic moduli of the SG and SS are also derived in regard of lattice size and arm-tubes’ diameter. Most important finding is that the increase of the arm-tubes’ diameter increases the elastic modulus of the SG and decreases that of the SS significantly. This contradictory effect is explained in terms of mechanics of load-transfer in the lattices. For all super-structures, extreme failure strains (18–76%), indicatory of their superior flexibility, are predicted. All simulations were performed under slight computational times since, in essence, beam FE models had to be solved. The inference drawn from the findings of the paper is that the EBC shows a potentiality in modeling CNT-based nanostructures owing mainly to its computational ease.

Electrical characterization of carbon nanotube Y-junctions: a foundation for new nanoelectronics

A review on the syntheses and electrical characterization of Y-shaped multi-walled carbon nanotube morphologies is presented. Modified thermal CVD processes, using Ti precursors, are used to grow Y-junctions of different geometries and distribution of catalyst particles. It has been established that novel electrical switching behavior is feasible, where any one of the three branches of the Y-junction can be used for modulating the electrical current flow through the other two branches. Current blocking behavior, leading to perfect rectification, is seen which could be related to the interplay of the carrier lifetime and the transit time. The overall goal is to investigate the possibility of obtaining novel functionality at the nanoscale, which can lead to new device paradigms.

Growth and Structure of Carbon Nanotube Y-Junctions

The effect of a catalyst on the growth and structure of carbon nanotube Y-junctions (CNTYs) using chemical vapor deposition has been investigated. Cobalt-, magnesium-, and calcium-nitrates are utilized as precursors of catalysts Co, Mg, Ca, Co/Mg, Co/Ca, and Mg/Ca for CNTY synthesis. Experimental result shows that Co/Mg or Co/Ca can grow CNTYs with straight branches while Co, Mg, Ca, and Mg/Ca will not grow any CNTYs, indicating that only combinations of Co with Mg or Ca will facilitate the formation of CNTYs. In addition, the effect of the carbon source on the formation of CNTYs has also been studied. It is found that thiophene (C4H4S) can promote the formation of CNTYs, while other sources such as methane (CH4) and acetylene (C2H2) cannot. The result shows that both the catalyst and the carbon source substantially affect the formation of CNTYs.

Electrical Transport in Carbon Nanotube Y-junctions- a Paradigm for Novel Functionality at the Nanoscale

AbstractCarbon Nanotube (CNT) morphologies with a self-contained gate, such as Y-junctions, offer a new way of exploiting features unique to the nanoscale, such as quantum ballistic transport. The advantages of low power and high frequency operation can then be applied to the fabrication of novel devices. Several other novel functionalities in Y- CNTs, including rectification, switching, high-frequency performance, and logic gates have been experimentally verified1. Y-CNT geometry dependent current blocking behavior, as a function of annealing temperature has also been observed. In view of the above observations, we propose that Y-CNTs can be used as prototypical nanoelectronic components.

Novel electrical switching behaviour and logic in carbon nanotube Y-junctions

Carbon-nanotube-based electronics offers significant potential as a nanoscale alternative to silicon-based devices for molecular electronics technologies. Here, we show evidence for a dramatic electrical switching behaviour in a Y-junction carbon-nanotube morphology. We observe an abrupt modulation of the current from an on- to an off-state, presumably mediated by defects and the topology of the junction. The mutual interaction of the electron currents in the three branches of the Y-junction is shown to be the basis for a potentially new logic device. This is the first time that such switching and logic functionalities have been experimentally demonstrated in Y-junction nanotubes without the need for an external gate. A class of nanoelectronic architecture and functionality, which extends well beyond conventional field-effect transistor technologies, is now possible.

Intrinsic electron transport properties of carbon nanotube Y-junctions

The electron transport properties of three-terminal carbon-nanotube junctions are investigated within the Landauer theory of quantum conductance. Using a realistic tight-binding Hamiltonian, we demonstrate that the experimentally observed rectifying behavior is not an intrinsic property of the junction, but rather of the contact geometry. When semiconducting nanotubes are connected to metallic leads, nontransmitting states are induced at the nanotube–metal interface, leading to asymmetric transmission curves and potentially rectifying behavior of the nanodevice.

Scanning tunneling microscopy and spectroscopy of Y-junction in carbon nanotubes

Scanning tunneling microscopy and spectroscopy were used to observe the variations of electronic structure on the carbon nanotube Y-junction. The electronic structure derived from tunneling conductance maps showed natural metallic–metallic and semiconducting–metallic transitions close to the Y-junction, and the occurrence of metallic character of the whole Y-junction with the presence of additional resonant state at energy of 0.2 eV below the Fermi level. It is suggested that the state originates from heptagons forming the junction.

Rectification properties of carbon nanotube "Y-junctions".

Quantum conductivity of single-wall carbon nanotube Y-junctions is calculated. The current versus voltage characteristics of these junctions show asymmetry and rectification, in agreement with recent experimental results. Furthermore, rectification is found to be independent of the angle between the branches of these junctions, indicating this to be an intrinsic property of symmetric Y-junctions. The implications for the Y-junction to function as a nanoscale molecular electronic switch are investigated.

Conductance in nanotube Y-junctions

We characterise the electronic properties of triangulenes and study their use as building blocks in nanotube metallic Y-junctions. We calculate the ballistic conductance of such junctions using the Landauer formalism, and identify the existence of a non-conduction energy window when the system has a C 3 axis centered on a six-membered ring. Such a system can exploit a local C 6 symmetry to stabilize the central region of the Y-junction, thereby opening a band gap.