Comparative density functional theory study on the band gap, effective mass and optical properties of graphene monolayer on SiC(0001) substrate

The semiconductor characteristic has never been shown, despite the fact that various Density Functional Theory (DFT) approaches have been applied to ascertain the electronic band structure of the graphene monolayer (GML) over the Si-terminated SiC surface. In this study, using an accurate Meta Generalized Gradient Approximation (MGGA) functional, the results showed that the GML@SiC (0001) exhibits a straight band gap of 0.57 eV along the K -> K in the reciprocal space, while Generalized Gradient Approximation (GGA) and HSE06 (Heyd-ScuseriaErnzerhof) hybrid functionals anticipated the metallic properties of GML. Different functionals display distinct electronic trends is due to how they mathematically treat electron self-interaction, orbital inhomogeneity via kinetic energy density tau (r) and nonlocal screening at a heterogeneous 2D(GML)/3D(SiC) interface. More, the lower estimated effective mass (m*) of electrons in GML calculated by GGA and HSE06 functionals with respect to MGGA, suggests minor interaction between photon-charge carriers of GML with the substrate. While the results corresponded to Im (omega) part of dielectric constants showed the presence of the first optical peak at 36-48 THz using different functionals, the high Re(omega) value of 28.03 has been calculated for GML@SiC(0001) by MGGA functional. Since Graphene GML@SiC (0001) is a premier platform for wafer-scale electronic devices, its main uses include high-frequency electronics, quantum metrology standards, and environmental sensing, and for this reason, the present study would help to utilize the graphene-based heterostructures for enabling advanced, tunable, and efficient optoelectronic devices.