Junctions of carbon nanotubes

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. 

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

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],... 

In the framework of semi-empirical method PM3 (worked out by Stewart [2,3] especially for calculation of electronic structure of carbon-contained organic molecules) the calculations of equilibrium configurations, full energy, heat of formation and electronic structure of different types of T-junctions of carbon zigzag and armchair nanotubes were done. 

The formation of junctions in carbon nanotubes is important for use in electronic application. The SWNTs have been shown to react with silicon and transition metals and form metal carbide nanorods and nanoparticles at high temperature under high vacuum. A heterojunction interface with metal carbide at the tips of SWNTs is possible. Silicon and metal substrates such as Ti and Nb have been used with SWNTs to form long SiC, TiC, and NbC nanorods respectively. A small number of SWNTs with partial reaction are found to have coimected to SiC nanorods (Figure 15). The formation of such a carbide heterojunctions in carbon nanotubes with... 

Nanometer-Sized Electronic Devices The possible use of carbon nanotubes in nanoelectronics has aroused considerable interest. Dramatic recent advances have fueled speculation that nanotubes (SWNTs) will be useful for downsizing circuit dimensions. Because of their unique electronic properties, SWNTs can be interfaced with other materials to form novel heterostructures [156]. The simplest device one can imagine with carbon nanotubes is that involving a bend or a kink, arising from the presence of a diametrically opposite pentagon-heptagon pair. The resultant junction connects two nanotubes of different chirality and hence of different electronic structure, leading to the realization of an intramolecular device. Such a device in SWNTs is found to behave like a diode rectifier [157]. Silicon nanowire-carbon nanotube heterojunctions do indeed exhibit a rectification behavior [158]. 

One of the most promising applications of fullerene molecules is nanoelectronics. Recently, several groups have reported the results of ab initio calculations of current-volt characteristics of the fullerene molecule [94,95]. These investigations were stimulated by scanning tunneling microscopy (STM) experiments in which the C o molecules were adsorbed on metallic surfaces [96, 97] as well as the break-junction experiments [98] and the demonstration of a prototype of a molecular transistor on the basis of carbon nanotube [99]. 

Figure 14 Different types of carbon nanotubes formed by irradiation (A) and CVD synthesis (B). (A) Cross-linking of SWNTs using 60s electron irradiation (1.25 MeV with beam intensity ca. 10 Acm ) at 800 °C (a) before irradiation and (b) after irradiation. (Reprinted with permission from M. Terrones, F. Banhart, N. Grobert, J.-C. Charlier, ff. Terrones, and P.M. Ajayan, Phys. Rev. Lett, 2002, 89, 075505. 2002 by the American Physical Society.) (B) Y -Junction MWNTs synthesized using nickelocene with thiophene at 1000 °C. (Ref. 91. Reproduced by permission of American Institute of Physics)...

Lee YH, Yoo JM, Lee JH Ju BK et al. (2006) All-carbon nanotube-based junction with virtual source and drain of carbon nanotubes by in situ one-step process for practical integrated nanoelectronics. Appl. Phys. Lett. 89 243104—243107. 

Bandam PR (2007) Electrical characterization of carbon nanotube Y-junctions A foundation for new nanoelectronics. J. Mater. Sci. 42 1809-1818. 

Krasheninnikov, A. V., Nordlund, K., Keinonen, J., and F. Banhart. 2003. Making junctions between carbon nanotubes using an ion beam. Nuclear Instruments ami Methods in Physics Research B 202 224-229. Krauser, J., ZoUondz, J.-H., Weidinger, A., and C. Traulmann. 2003. Conductivity of nanometer-sized ion tracks in diamond-hke carbon films. Journal of Applied Physics 94 1959—1964. 

Shape Analysis of Carbon Nanotubes, Nanotori and Nanotube Junctions... 

The resistance to phonon movement from one nanotube to another through the junction will hinder phonon movement and, hence, limit the thermal conductivity. The low thermal conductivity could be partly due to the non-uniform diameter and size, as well as the defects in and the nanoscale dimension of MWCNTs. However, the numerous junctions between carbon nanotubes involved in forming a conductive path and the exceptionally low thermal conductance at the interface, are believed to be the main reason for the low thermal conductivity. The effect of reducing the thermal conductivity is the transfer of phonons from nanotube to nanotube. This transition occurs by direct coupling between CNTs, in the case of the improper impregnated ropes,... 

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

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