Electronic Properties and Band Gaps of Single-Wall Carbon Nanotubes Using <i>π</i> Orbitals Tight-Binding Model: A Comparative Study with <i>Ab Initio</i> Density Functional Theory

Abstract

Semiconducting single-wall carbon nanotubes (SWCNTs) have already emerged as a promising candidate for molecular electronics and photovoltaic applications including solar cells. Any application of semiconducting SWCNTs is primarily related to proper information about its bandgap. In this work, the impact of the chirality indices and diameters of a series of armchair and zigzag SWCNTs on the electronic properties (band gap, electronic band structure and density of states (DOS)) are investigated using semi-empirical π orbitals tight-binding (TB) method. The results indicate that the electronic behaviour of the nanotubes changes according to chirality, the total number of electronic sub-bands gets increased when the chirality increases and Van Hove singularities (VHs) appear in its electronic DOS. We have found that for small diameter tubes (less than 0.8 nm), the calculated band gaps don’t agree with DFT calculations based on ab-initio (LDA and GGA) methods, which shows that the semi-empirical TB method including π orbitals only is not sufficient to give a reasonable description of small nanotubes. All Obtained results are in good agreement with previous studies. Semiconducting SWCNTs used in this study are particularly well-suited for the nanoelectronic devices and optoelectronic applications with their direct bandgap and optical transitions, while metallic SWCNTs are considered to be ideal candidates for variety of future nanoelectronic applications such as nanocircuit interconnects and power transmission cables.