Carbon nanotube junction

The conductive properties of SWCNTs were predicted to depend on the helicity and the diameter of the nanotube [112, 145]. Nanotubes can behave either as metals or semiconductors depending upon how the tube is rolled up. The armchair nanotubes are metallic whereas the rest of them are semiconductive. The conductance through carbon nanotube junctions is highly dependent on the CNT/metal contact [146]. The first measurement of conductance on CNTs was made on a metallic nanotube connected between two Pt electrodes on top of a Si/Si02 substrate and it was observed that individual metallic SWCNTs behave as quantum wires [147]. A third electrode placed nearby was used as a gate electrode, but the conductance had a minor dependence on the gate voltage for metallic nanotubes at room temperature. The conductance of metallic nanotubes surpasses the best known metals because the... 

Kiricsi, I., Konya, Z., Niesz, K., Koos, A.A., Biro, L.P., Synthesis procedures for production of carbon nanotube junctions, Proceedings ofSPIE - The International Society for Optical Engineering, 5118, 2003, 280-287. 

Upon reacting SWCNT-acyl chlorides with a,co-diamines such as tripropylene-tetramine as molecular linker and subsequent diamide formation with another SWCNT, Roth and coworkers [109, 110] and Kiricsi et al. [Ill] succeeded in the interconnection of tubes and the formation of carbon nanotube junctions. End-to-end (Scheme 1.6a) and end-to-side nanotube interconnections (Scheme 1.6b) were formed and observed by AFM. Statistical analyses of the AFM images showed around 30% junctions in functionalized material [42],... 

He, L., Lu, J.Q., and Jiang, H.Q. (2009) Controlled carbon-nanotube Junctions self-assembled from graphene nanoribbons. Small, 5, 2802 - 2806. 

Graovac A, Laszlo I, Plavsic D, Pisanski T (2008) Shape analysis of carbon nanotube junctions, MATCH. Commun Math Comput Chem 60 917-926... 

K. Matsuura, K. Hayashi, and N. Kimizuka, Lectin-mediated supramolecular junctions of galactose-derivatized single-walled carbon nanotubes, Chem. Lett., 32 (2003) 212-213. 

Stranks, S. D. Weisspfennig, C. Parkinson, P. Johnston, M. B. Herz, L. M. Nicholas, R. J., Ultrafast charge separation at a polymer-single-walled carbon nanotube molecular junction. Nano Lett. 2011,11, 66. 

Louie, S.G. (2001) in Electronic Properties, Junctions and Defects of Carbon Nanotubes, Topics in Applied Physics 80 (eds M.S. Dresselhaus,... 

Other alternatives for the construction of CNT based FETs have been explored. For example, carbon nanotube branches with Y shape can be used directly as transistors where the modulation of the current from an ON to an OFF state is presumably mediated by the defects and the morphology of the junction (see Fig. 19) [170, 171]. Carbon nanotube based FETs can be gated by an electrode immersed in a solution, or by charged molecules in solution (proteins, DNA, etc.) which opens a huge field of applications in sensors [172-176] (see Fig. 20). Their ability to operate under biological conditions allows their direct use or integration into biological systems [177]. 

Bandaru PR, Daraio C, Jin S et al (2005) Novel electrical switching behaviour and logic in carbon nanotube Y-Junctions. Nat Mater 4 663-666... 

Kim D, Huang J, Rao BK et al (2006) Pseudo Y-junction single-walled carbon nanotube based ambipolar transistor operating at room temperature. IEEE Trans Nanotechnol 5 731-736... 

All potentials vs. screen-printed Ag/AgCl pseudo-reference, except values marked with asterisk ( ), which are vs. Ag/3M AgCl double-junction reference electrode, and values marked with dagger CfO, which are vs. saturated calomel. Abbreviations CoPC cobalt phthalocyanine, SPCE screen-printed carbon electrode, GOD glucose oxidase, MWCNT multi-walled carbon nanotubes, NAD nicotinamide adenine dinucleotide, PQQ pyrroloquinoline quinone, FIA flow injection analysis. 

Single-walled carbon nanotubes (SWNTs) had been considered for the crossbar components of the defect-tolerant molecular computers but they have been found to be too difficult to handle due to their insolubility and their tendency to form bundles or ropes. Instead, metallic nanowires have become the materials of choice used in the construction of the crossbar devices, with ultrahigh-density lattices and circuits being built, having groups of nanowires 8 nm in diameter and 16 nm apart in layers perpendicular to each other to create nanowire junction densities of 1011 per cm2.52 The process does not depend on self-assembly but rather on molecular beam epitaxy. 

Keywords junctions of carbon nanotubes, variable diameter, molecular simulations, quantum-chemical calculations, modeling. 

Quantum chemistry computations based on employing of PC Gamess version of semi-empirical PM3-method [1-2] allows to define equilibrium configuration and calculate electronic structure of some of the simplest Y-junctions of carbon nanotubes, which have slang name twig . On the place of nanotubes conjunction defective cycles appear. Their type, number and mutual displacement can be enough various even in comparatively simple cases. Only the part of obtained results is presented here. 

Scanning tunneling spectroscopic studies of Y-junction carbon nanotubes show interesting diodelike device characteristics at the junctions. A typical /—V curve obtained from positioning the tip atop a Y-Junction (the point of contact between the three arms) as well as on the individual arms of the Y-junction is shown in Figure 10. The I—V plot at the junction is asymmetric (Figure 10b)... 

FIGURE 8. (a, b) TEM images of Y-junction carbon nanotubes obtained by the pyrolysis of nickel ocene and thiophene at 1000 °C.a... 

FIGURE 10. /— V curves collected from different points in a Y-junction carbon nanotube (a) from one of the arms away from the junction and (b) from the junction of the three arms. Inset show plots of d//dl/vs bias voltage. The observed gaps are indicated by... 

Menon. M. Srivastava. D. Carbon nanotube "T junctions" Nanoscale metal-semiconductor-metal contact devices. Phys. Rev. Lett. 1997 79. 4453. 

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