The Effect of Strain on the Electronic Properties of Graphene Nanoribbons

Abstract

Graphene nano-ribbons (GNRs) have great potential for the application of field effect transistors (FET). However, in the graphene transfer and semiconductor device fabrication process, due to the thermal expansion and lattice mismatch between dissimilar materials, internal stress is easily formed in GNRs, leading to the undesirable deformation. Thus, the electronic states of GNRs are usually modified, which may degrade the reliability of GNRs-based nano-devices. We investigated the effect of tensile, bending and folding deformations on the electronic states of armchair GNRs (AGNRs) based on density functional theory (DFT) calculation and found that the electronic structure of AGNRs is very sensitive to the external deformation. When a uniaxial tensile stress is applied to AGNRs with width Na = 10, the band structure is modified, leading to the change in band gap approximately from 0 eV to 1.0 eV. Due to the orbital hybridization, the band gaps of bended and folded AGNRs decrease significantly when the maximum local dihedral angle exceeds a critical value. In order to clarify the effect of external stress on the electronic conductivity of GNRs, the current through AGNRs under uniaxial tension is analyzed using a non-equilibrium Green’s function approach based on π-orbital tight-binding approximation. It is found that at a relative large ribbon length Ns = 20, the uniaxial tensile strain can modify the band gap of AGNRs, leading to the change in the electronic conductivity. Moreover, the current-strain (I-ε) relationship of AGNRs changes significantly as the change in the length of strained area.