Effect of substitutional and vacancy defects on the electrical and mechanical properties of 2D-hexagonal boron nitride.

Abstract

Defects in the nanoscale are common in the 2D materials irrespective of the fabricated method. Material performance gets significantly affected due to the presence of defects in 2D materials. In the present study, electronic and mechanical properties of 2D-hexagonal boron nitride (hBN) are investigated. At the electronic scale, the formation energies, band structures were obtained for pristine and defected hBN. The substitutional defects of carbon (C-at-NS, C-at-BS) and oxygen (O-at-NS, O-at-BS) at boron and nitrogen sites, single vacancy defects (BV, NV) and triangular vacancies (3B + N)v and (3N + B)v of boron and nitrogen, and Stone-Thrower-Wales (STW) type-1 and type-2 defects were considered. We found that with the inclusion of defects in 2D-hBN, the bandgap decreases, and carbon substitution at the boron site produces n-type characteristics, whereas substitution of carbon at the nitrogen site produces p-type characteristics. Boron vacancies increased the p-type character. At the atomistic scale, stiffness, ultimate tensile strength, and fracture strain were simulated for the pristine and defected hBN with molecular dynamics (MD) simulations using Tersoff potential. We found that the vacancy defects dominated by Boron atoms are energetically favorable and shift the electric conductivity from insulating to conducting. The stiffness and ultimate tensile strain of the 2D-hBN in the zigzag direction are higher than that of armchair direction. A strength reduction of around ~ 50% is observed with a defect concentration of 2.1%. It is observed that pristine and defective 2D-hBN is stronger in ZZ than AC configuration. Graphical abstract.