Abstract
A first principles based density functional theory (DFT) has been employed to identify the signature of Stone–Wales (SW) defects in semiconducting graphene quantum dot (GQD). Results show that the G mode in the Raman spectra of GQD has been red shifted to 1544.21 cm − 1 in the presence of 2.08% SW defect concentration. In addition, the intensity ratio between a robust low intense contraction–elongation mode and G mode is found to be reduced for the defected structure. We have also observed a Raman mode at 1674.04 cm − 1 due to the solo contribution of the defected bond. The increase in defect concentration, however, reduces the stability of the structures. As a consequence, the systems undergo structural buckling due to the presence of SW defect generated additional stresses. We have further explored that the 1615.45 cm − 1 Raman mode and 1619.29 cm − 1 infra-red mode are due to the collective stretching of two distinct SW defects separated at a distance 7.98 Å. Therefore, this is the smallest separation between the SW defects for their distinct existence. The pristine structure possesses maximum electrical conductivity and the same reduces to 0.37 times for 2.08% SW defect. On the other hand, the work function is reduced in the presence of defects except for the structure with SW defects separated at 7.98 Å. All these results will serve as an important reference to facilitate the potential applications of GQD based nano-devices with inherent topological SW defects.
Highlights
The successful experimental fabrication of the two dimensional (2D) nanostructure graphene was a path breaking event in the field of material science
Graphene quantum dots (GQDs) are very small fragments of graphene, where the motion of electrons is confined in three spatial directions
The GQDs are generally semiconducting in nature and the band gap can be tuned by varying the shape, size and surface chemistry [14,15,16]
Summary
The successful experimental fabrication of the two dimensional (2D) nanostructure graphene was a path breaking event in the field of material science. It is evident from previous reports that concentration as well as the specific positions of the defects crucially determine the hybridization and stability of the systems These modifications have immense impact on the electronic band structure [38], and, on the conductivity of the system [39,40]. Motivated by the above discussions, we have systematically investigated the effect of SW defects on the vibrational and electronic properties of the graphene quantum dot (GQD). Afterwards, we have extensively discussed the impact on the Raman and IR spectra of the GQD, followed by the variation in electronic properties i.e., dipole moment variation, effect on conductivity, work function, energy gap, etc. We expect that these results will broaden the possibilities of GQDs to be used in nano-electronic devices
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
