Geometry of Multi-Tube Carbon Clusters and Electronic Transmission in Nanotube Contacts

Abstract

The geometry of general structures based on carbon multi-tube contacts is discussed and some characteristics of the electronic transport in a metal-semiconductor (6,0)–(5,1) nanotube junction are presented. A theoretic method allowing us to construct the structure of a multi-tube carbon cluster composed of two or more tubes of different characteristics is developed by introducing heptagonal and pentagonal defects in the hexagonal graphitic net. By defining the ‘strip’ concept, we propose a general classification and notation of these structures and develop a method to determine the indices of the outgoing tubes from the multi-tube structure. We also demonstrate that is always possible to connect two tubes of arbitrary indices with only one heptagon-pentagon pair, and the method to obtain the specific geometry of the two-tube union is presented. Electron packet movement in a (6,0)–(5,1) nanotube junction is analysed by numerical integration of the nonstationary Schrodinger equation in the π -electron tight-binding approximation, using the norm-conserving numeric scheme based on a Pade approach of the evolution operator. The method developed can be applied to a general contact of two arbitrary nanotubes.