Search query: Carbon nanotube intramolecular junctions

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abstract: The ultimate device miniaturization would be to use individual molecules as functional devices. Single wall carbon nanotubes (SWNTs) are promising candidates for achieving this: depending on their diameter and chirality, they are either one dimensional metals or semiconductors. Single electron transistors employing metallic nanotubes and field effect transistors employing semiconducting nanotubes have been demonstrated. Intramolecular devices have also been proposed which should display a range of other device functions. For example, by introducing a pentagon and a heptagon into the hexagonal carbon lattice, two tube segments with different atomic and electronic structures can be seamlessly fused together to create intramolecular metal metal, metal semiconductor, or semiconductor semiconductor junctions. Here we report electrical transport measurements on SWNTs with intramolecular junctions. We find that a metal semiconductor junction behaves like a rectifying diode with nonlinear transport characteristics that are strongly asymmetric with respect to bias polarity. In the case of a metal metal junction, the conductance appears to be strongly suppressed and it displays a power law dependence on temperatures and applied voltage, consistent with tunnelling between the ends of two Luttinger liquids. Our results emphasize the need to consider screening and electron interactions when designing and modelling molecular devices. Realization of carbon based molecular electronics will require future efforts in the controlled production of these intramolecular nanotube junctions.
author_names: Zhen Yao

Henk W Ch Postma

Leon Balents

Cees Dekker
title: Carbon nanotube intramolecular junctions
venue: Nature
year: 1999

abstract: Leveraging the unique properties of single walled carbon nanotube (SWNT) intramolecular junctions (IMJs) in innovative nanodevices and next generation nanoelectronics requires controllable, repeatable, and large scale preparation, together with rapid identification and comprehensive characterization of such structures. Here we demonstrate SWNT IMJs through directly growing ultralong SWNTs on trenched substrates. It is found that the trench configurations introduce axial strain in partially suspended nanotubes, and promote bending deformation in the vicinity of the trench edges. As a result, the lattice and electronic structure of the nanotubes can be locally modified, to form IMJs in the deformation regions. The trench patterns also enable pre defining the formation locations of SWNT IMJs, facilitating the rapid identification. Elaborate Raman characterization has verified the formation of SWNT IMJs and identified their types. Rectifying behavior has been observed by electrical measurements on the as prepared semiconducting semiconducting (S S) junction.
author_names: Jianing An

Zhaoyao Zhan

Gengzhi Sun

Hari Mohan

Jinyuan Zhou

Young-jin Kim

Lianxi Zheng
title: Direct Preparation of Carbon Nanotube Intramolecular Junctions on Structured Substrates
venue: Scientific reports
year: 2016

abstract: In this letter, graded pillared graphene structures with carbon nanotube graphene intramolecular junctions are demonstrated to exhibit ultrahigh thermal rectification. The designed graded two stage pillared graphene structures are shown to have rectification values of 790.8 and 1173.0% at average temperatures 300 and 200 K, respectively. The ultrahigh thermal rectification is found to be a result of the obvious phonon spectra mismatch before and after reversing the applied thermal bias. This outcome is attributed to both the device shape asymmetry and the size asymmetric boundary thermal contacts. We also find that the significant and stable standing waves that exist in graded two stage pillared graphene structures play an important role in this kind of thermal rectifier, and are responsible for the ultrahigh thermal rectification of the two stage ones as well. Our work demonstrates that pillared graphene structure with SWCNT graphene intramolecular junctions is an excellent and promising phononic device.
author_names: Xueming Yang

Dapeng Yu

Bing-Yang Cao

Albert C To
title: Ultrahigh Thermal Rectification in Pillared Graphene Structure with Carbon Nanotube Graphene Intramolecular Junctions.
venue: ACS applied materials interfaces
year: 2017

abstract: Highly efficient carbon based 1D light emitting devices require multi quantum well heterostructures with sensitive optical properties. However, carbon nanotubes (CNTs) based composites become much worse than expected and most of their applications such as field emission are thwarted because dispersing CNTs among one another is difficult. We demonstrate that such sensitive optical and limited field emission properties can be attained and improved, respectively, through the use of ZnO nanocrystal selective quantum well heterostructures grown on carbon nanotubes to fabricate carbon zinc oxide (CZO) nanotubes. ZnO can be effectively and uniformly decorated on the carbon nanotubes intramolecular junctions with abundant functional groups and also with large surface adsorption area produced by CNTs surface plasma pre treatments at room temperature. The cathodoluminescence (CL) spectrum of the CZO nanotubes exhibits a weak UV emission peak and two distinct strong green emission peaks at 2.51 eV and at 2.4 eV, attributed to zinc rich ZnO band to donor transitions and oxygen rich ZnO band to acceptor transitions, respectively. Furthermore, the CZO nanotubes reach an extremely low turn on field of 0.1 V mm 1, low threshold field of 3.1 V mm 1, but high field enhancement factor b of 110 x 103. The field emission properties are dramatically enhanced by ZnO quantum dots decorated on the carbon nanotube intramolecular junctions, which not only provide extra electron emission paths and higher carrier concentrations, but also protect the emitter from ion bombardment during operation.
author_names: Chia-Te Hu

Jyh Ming Wu

Jien-Wei Yeh

Han Chang Shih
title: ZnO quantum dots decorated on optimized carbon nanotube intramolecular junctions exhibit superior field emission properties
year: 2016

abstract: The longitudinal vibration band gaps in periodic (n, 0) (2n, 0) single walled carbon nanotube(SWCNT) intramolecular junctions(IMJs) are investigated based on the finite element calculation. The frequency ranges of band gaps in frequency response functions(FRF) simulated by finite element method (FEM) show good agreement with those in band structure obtained by simple spring mass model. Moreover, a comprehensive parametric study is also conducted to highlight the influences of the geometrical parameters such as the size of unit cell, component ratios of the IMJs and diameters of the CNT segments as well as geometric imperfections on the first band gap. The results show that the frequency ranges and the bandwidth of the gap strongly depend on the geometrical parameters. Furthermore, the influences of geometrical parameters on gaps are nuanced in IMJs with different topological defects. The existence of vibration band gaps in periodic IMJs lends a new insight into the development of CNT based nano devices in.
author_names: Jiaqian Li

Hai-jun Shen
title: Analysis of longitudinal vibration band gaps in periodic carbon nanotube intramolecular junctions using finite element method
year: 2015

abstract: The dispersion of longitudinal and transverse waves in (n,0) (2n,0) intramolecular junctions (IMJs) are investigated using an atomistic finite element method (FEM) The transient responses of IMJs with different connection types subjected to harmonic incident wave were modelled using three dimensional elastic beams of carbon bonds and point masses. The linkage between the force field constants of molecular mechanics and input parameters of beam and mass elements was established through the molecular structural mechanics approach. The wave dispersion simulated by FEM shows good agreement with that of the non local elastic model in a wide frequency range up to the terahertz region. It is shown that both the microstructure of conical part (connection part) and the coupling of longitudinal vibration and transverse vibration brought by the conicity play important roles in the dispersion of longitudinal and transverse wave in a single walled IMJ. The amplitude decay of longitudinal wave depended on the distance propagating; the wavelength and the structure in connection part are examined. The results show that the dispersion of the decay of the wave amplitude in IMJ with less pentagon heptagon defects has a better agreement with analytical results of macroscopic conical shell.
author_names: Jiaqian Li

Hai-jun Shen
title: Wave propagation in carbon nanotube intramolecular junctions: finite element calculations
year: 2015

abstract: Abstract The mechanical properties of single walled carbon nanotubes with one dimensional intramolecular junctions (CNT IMJs) are investigated, using first principles density functional theory calculations. The effects of pentagon heptagon (5 7) defects (a pair of five and seven membered rings) at a junction on the Young's modulus, tensile strength, and breaking strain of CNT IMJs are discussed from the viewpoint of charge density and interatomic distance. Our calculations indicate that the deformation concentration on a seven membered ring causes the strength and elongation of CNT IMJs to decrease. It is found that the tensile strength and breaking strain of CNT IMJs depend on the position of 5 7 defects, while these properties of CNT IMJs are not significantly affected by the number of 5 7 defects. The applicability of the AIREBO classical interatomic potential in the simulation of the tensile deformation in CNT IMJs is also discussed.
author_names: Yusuke Kinoshita

Motoyuki Murashima

Masaki Kawachi

Nobutada Ohno
title: First principles study of mechanical properties of one dimensional carbon nanotube intramolecular junctions
year: 2013

abstract: We present results of a reverse non equilibrium molecular dynamics study of thermal transport in single walled carbon nanotube (SWCNT) graphene junctions comprised of carbon carbon (C C) bonds with either sp2 or mixed sp2/sp3 hybridization. In both cases, a finite interfacial thermal resistance is observed at the SWCNT graphene junctions for thermal transport in the out of plane direction. The interfacial thermal resistance at the junctions is attributed to the combined effects of scattering of the phonons at the SWCNT graphene junctions due to the presence of distorted sp2 bonds in the junction region and the change in dimensionality of the medium along the phonon transport path as the phonons propagate from SWCNT pillars (quasi 1D) to graphene sheet (2D) and then again to SWCNTs. Moreover, the thermal resistance is found to depend on the C C bond hybridization at the intramolecular junctions with mixed sp2/sp3 hybridization showing a higher interfacial resistance when compared to pure sp2 bonding. Therm.
author_names: Jungkyu Park

Vikas Prakash
title: Phonon scattering and thermal conductivity of pillared graphene structures with carbon nanotube graphene intramolecular junctions
year: 2014

abstract: Abstract Carbon nanotube based intramolecular junctions can function as rectifying diodes and switches in circuits and thus possesses the promising potential to be applied in nano scale electronic devices. Due to their slender and unsymmetrical geometry, intramolecular junctions are prone to buckling under compression and the resulting structural instability will eventually leads to structural or electrical failure. Thus, it is important to explore the mechanical behaviors of intramolecular junctions subject to compressive loads. In this study, molecular dynamical simulations are carried out to investigate the compressive behaviors of intramolecular junctions at finite temperature, while carbon nanotubes are also studied as reference. The simulation results indicate that the strain rate effect is negligible within relatively low loading rate range but the critical strain increases significantly under higher loading rate. At an extremely high strain rate, the intramolecular junctions will crush immediately. It is also predicted that local deformation will be introduced at high environmental temperature. Moreover, with increasing tube length, the instability mode of the intramolecular junctions transfers from shell buckling to column buckling and the critical aspect ratio is lower than that of carbon nanotubes due to presence of the Stone Wales defects.
author_names: Ming Li

Zhan Kang

Peiying Yang

Xianhong Meng

Yanjun Lu
title: Molecular dynamics study on buckling of single wall carbon nanotube based intramolecular junctions and influence factors
year: 2013

abstract: Nitrogen doped carbon nanotubes (CN x /carbon nanotube intramolecular junctions were prepared by a simple continuous chemical vapour deposition (CVD) method at 650 degC. The catalyst was obtained by calcination of a layered double hydroxide precursor containing Fe and Mg. By switching between hexane and ethylenediamine repeatedly in the CVD process, multiple intramolecular junctions composed of CN x with a bamboo like structure and empty hollow carbon nanotubes were observed, and such different structures at both sides of the junctions indicated some interesting properties and offered potential applications for future nanodevices. Keywords: Nitrogen doped carbon nanotubes, junction, chemical vapour deposition
author_names: Yong Cao

Bingtao Liu

Qingze Jiao

Yun-Peng Zhao
title: Preparation of CN x /Carbon Nanotube Intramolecular Junctions by Switching Gas Sources in Continuous Chemical Vapour Deposition
year: 2011