Theoretical prediction of 2D XI₂ (X=Si, Ge, Sn, Pb) monolayers by density functional theory

Two dimensional monolayer semiconductors play an important role in designing opto-electronic devices for applications. In this paper, through the properties of the density functional theory, by running a series of first principles computations, the stability and the electronic properties of XI₂ (X = Si, Ge, Sn, Pb) monolayer structures is investigated. Our calculations indicate that 2D SiI₂, GeI₂, SnI₂, and PbI₂ monolayer materials show good stabilities. Accessing on their electronic properties indicates that they have semiconducting nature with strain tunable indirect band gaps of 2.38, 2.80, 2.72, and 3.23 eV respectively which are obtained by functional (HSE06) level of theory. The obtained electronic properties can be effectively tuned by strain effects suggests the predicted 2D monolayer materials for application in new opto-electronic devices.