An ab initio investigation of monolayer and bilayer graphene nanoribbon based on different basis sets

Abstract

We investigated the electronic structure of monolayer and bilayer graphene nanoribbon with armchair edges (AGNRM and AGNRB respectively) based on Density Functional Theory using single-ζ (SZ) and double -ζ (polarized) (DZP) basis sets. We first optimize the atomic structure of an AGNRB and found that DZP is better suited to account for the interlayer Interaction. Next we calculate the energy band diagram of the AGNRM and AGNRB of different width, and study dependence of the band gap (Eg) on the widths. Like AGNRM, AGNR B also shows three different groups in terms of energy bandgap vs. width. In general, AGNRB is found to have a lower Eg than AGNRM. Especially for N=3p+2 family, while it is semiconducting for AGNRM, the Eg of AGNRB is very small and can be considered as metallic at room temperature. Furthermore, we investigate the relationship between Eg and the interlayer distance (D) of AGNR B. From our calculation, Eg is found to be strongly influenced by D and Egincreases as D increases. Finally, comparing solely on Eg we can see that both SZ and DZP calculations provide information on the three trends of the AGNRM and AGNRB, with small differences in the absolute values and hence it may be possible to use SZ for rapid preliminary investigation of the electronic properties of AGNR systems. © 2008 IEEE.