The effect of doping/dual-doping with nitrogen and silicon on the structural, electronic, and optical properties of graphene: first-principles study

In this study, the structural, electronic, and optical properties of pristine graphene and graphene doped/co-doped with (N, Si) atoms are examined using a first-principles investigation. However, pristine graphene is characterized by a unique electronic structure known as the zero band gap (Eg = 0 eV), and this gap was opened up after the addition of N and Si substitutions, where it became 0.2, 0.21, and 1.38 eV for graphene doped with nitrogen, silicon and double doped with both (N, Si), respectively. For the band gap and the density of states, many parameters have been studied such as the complex dielectric function, conductivity, absorption spectra, loss function, and refractive index. The absorption curve shows two sharp peaks for all structures, where their intensities become lower and shift slightly towards lower energy after doping graphene with N, Si, and N-Si, indicating that this doping introduces additional energy states in the graphene band structure, making the transition between states easier to achieve.