Manipulation of structural, electronic and transport properties of hydrogen-passivated graphene atomic sheet through vacancy defects: first-principles numerical simulations based on density-functional-theory along with tight-binding approximation

Using the first-principles procedure of density-functional-theory within tight-binding approximation and nonequilibrium Green's function formalism, this paper reports on the impact of vacancy defects on the structural, electronic and transport properties of hydrogen-passivated graphene atomic sheet. After the introduction of vacancy defects in graphene atomic sheet passivated with hydrogen atoms, apart from increase in band gap, a suppression is noted in the intensity of transmission channels and density of states arising from the long array deformations of the graphene sheet and a corresponding shift of the Fermi level. This in turn decreases the conductance of the defected graphene atomic sheet. In case of slow-ion bombardment method, the conductance of the sheet decreases slowly and its value of the order 10⁻⁶ S before vanishing the percolation drops to the order 10⁻¹⁰ as the percolation of the sheet is destroyed. But in case of fast bombardment the conductance of the sheet shows a linear drop before vanishing of the percolation of the sheet, and its value of the order 10⁻⁶ S before vanishing the percolation drops to the order 10⁻¹⁰ as the percolation of the sheet is destroyed. Furthermore, it is found that the atomic vacancy defects effectively terminate the original smooth sp²-hybrid network of 2D graphene atomic sheet that leads to modify its electronic and transport properties, especially a decrease in its electrical conductance. Interestingly, transmission spectrum of graphene atomic wire with large vacancy defects of 143 attains identical shape to that of a molecular benzene ring. (paper)