Electronic and Mechanical Properties of Super Carbon Nanotube Networks
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0963-Q15-07
Electronic and Mechanical Properties of Super Carbon Nanotube Networks Vitor R. Coluci1, Socrates O. Dantas2, Ado Jorio3, and Douglas s Galvao1 1 IFGW-UNICAMP, Campinas - Sao Paulo, 13081, Brazil 2 Dpto. Fisica - UFJF, Juiz de Fora - MG, 36036, Brazil 3 Dpto. Fisica - UFMG, Belo Horizonte, 30123, Brazil ABSTRACT Eletronic and mechanical properties of ordered carbon nanotube networks are studied using molecular dynamics simulations and tight-binding calculations. These networks are formed by single walled carbon nanotubes (SWNT) regularly connected by junctions. The use of different types of junctions (“Y”-, “X”-like junctions, for example) allows the construction of networks with different symmetries. These networks can be very flexible and the elastic deformation was associated with two main deformation mechanisms (bending and stretching ) of the constituents SWNTs. Rolling up the networks, “super” carbon nanotubes can be constructed. These super-tubes share some of the main electronic features of the SWNT which form them but important changes are predicted (e.g. reduction of bandgap value). Simulations of their deformations under tensile stress have revealed that the super-tubes are softer than the corresponding SWNT and that their rupture occur in higher strain values. * Corresponding author: [email protected] FAX: +551937885376 INTRODUCTION Carbon based materials present an enormous variety of forms and properties. Among these structures are graphite, diamond, fullerenes, and carbon nanotubes [1]. A single walled carbon nanotube (SWNT) can be considered heuristically as formed by rolling up a graphene sheet to make a seamless cylinder. Many attempts have been made in order to obtain carbon nanotube networks [2-8]. Most of the above mentioned works have produced random networks but more organized arrangements have also been obtained [7,8]. While organized networks consist mainly of ropes or bundles of SWNTs [7,8], recent achievements have shown the possibility of fabricating high oriented isolated SWNTs directly on top of substrate surfaces [9,10,11]. Ismach and Joselevich [11] have demonstrated the formation of crossbar networks by simultaneously using graphoepitaxy and field-directed growth of SWNTs by chemical vapor deposition. In those networks the nanotubes crossbar junctions are bonded by van der Waals interactions with the nanotubes radially deformed at the junctions. It has been experimentally observed and theoretically investigated [12] that covalent bonds can be formed between two crossing SWNTs when exposed to electron beam at high temperatures forming a stable junction. The coupling of the steps previously mentioned can lead to the possibility of fabrication of isolated ordered covalently joined SWNTs networks. These networks could be considered as the ultimate arrangement involving SWNTs which are constructed by using “X”, “Y”, or “T”-like junctions [12]. In this work we investigated the electronic and mechanical properties of ordered SWNTs networks (OSN) using tight-binding calculat
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