Bandgap engineering of porous graphene toward straintronics

The influence of Boron (B) and Nitrogen (N) impurities at various concentrations on the structural and electronic properties of a monolayer of porous graphene is investigated using first-principles calculations based on density functional theory (DFT), particularly in the presence of planar biaxial strain distributions. The results demonstrate that the pristine porous graphene sheet acts as a semiconductor with a direct bandgap of 2.326 eV at the K point. The substitution of a single carbon atom with a Boron (Nitrogen) atom shifts the Fermi energy to the valence (conduction) band, thereby transitioning the material from a semiconductor to a metallic state. However, replacing an adjacent pair of carbon atoms with a B-N pair maintains the semiconductor nature, though the bandgap value is reduced. Our investigation reveals that the porous graphene structure remains stable under a symmetrical biaxial planar strain up to an intensity of 10%, beyond which some C-C bonds reach the threshold of rupture. By applying uniaxial strain distributions along the symmetry lines, as well as tensile and compressive symmetrical biaxial strain distributions with different intensities (less than 10%), the bandgap can be continuously modulated over a wide range. Specifically, applying a symmetrical tensile biaxial strain with an intensity of 10% increases the bandgap value to 3.024 eV. Conversely, applying a symmetrical compressive biaxial strain with an intensity of 6% reduces the bandgap to 1.671 eV. In general, increasing the intensity of the tensile strain leads to an increase in the bandgap value, while increasing the intensity of the compressive strain causes its reduction. These quantitative results present high potential for practical applications in the fields of nano-electronics and nano-optoelectronics.