DFT study of electronic and optical properties of silicene functionalized with chemical groups

Abstract

In the last years, a band-gap tunability is particularly interesting for the fabrication of flexible and ultrathin optical devices since it is known from earlier studies that two-dimensional materials can display a much larger sunlight absorption than commonly employed semiconductors. Using density functional theory, we study the structural, electronic and optical properties such as dielectric function, absorption coefficient, conductivity, and a refractive index of silicene monolayer functionalized with chemical groups or atoms (i.e, X-Si-Y, Cl–Si–Br, and X'-Si-X' with X = Cl, F, or OH; Y = CN; X' = CN, CH, or NH). In this framework, by means of AIMD calculations, we show that they are dynamically stable, while their electronic band-gap, as obtained with the GGA approximation, ranges between 1.25 and 2.13 eV, except for CH–Si–CH and NH–Si–NH, which are found to be metallic. Additionally, we show that an external electric field can modify significantly the electronic structure of some of these systems.