Tight-Binding Calculation of Deformation and Band Gap of Single-Walled Carbon Nanotubes under Axial Tension and Radial Compression

Abstract

Application of carbon nanotubes (CNTs) to nanometer-scale electronic devices of the next generation is being highly expected owing to their prominent electronic properties and mechanical and chemical stability. Controlling local strain is a key issue to design and realize such devices because of the interplay between mechanical and electronic properties in carbon nanotubes. In this study, we performed semi-empirical tight-binding band calculation of single-walled carbon nanotubes (SWCNTs) with various chiral structures to investigate the deformation behavior and its relation to electronic properties. Firstly, we performed simulation of SWCNTs subject to axial tension, which is one of the simplest deformation modes, to investigate their mechanical properties and change in band gap energies. Pristine SWCNTs can hold high tensile strain. SWCNTs show transition between semiconducting and metallic features during tension, and the transition behavior depends on the chirality of the nanotubes. Secondly, we investigated the mechanical and electronic properties of SWCNTs under radial compression, as it is relatively easy to apply such deformation, for example by moving an AFM tip to a nanotube lying on a plate. SWCNTs are robust under large compression showing no bond breaking or rebonding. The mechanism of the peculiar elastic behavior is discussed. CNTs that have finite band gap energies (semiconducting) at unstrained state show transition to metallic state under radial compression