Two-dimensional cadmium selenide electronic and optical properties: first principles studies

摘要

Structural, electronic and optical properties of two-dimensional (2D) cadmium selenide (CdSe) structures with$2imes 2$ periodicities are investigated. First principles total energy calculations are performed within the periodic densityfunctional theory. Initially, the structural properties are determined using the local density approximation as implementedin the PWscf code of quantum ESPRESSO package. To investigate the electronic properties, the GW method is applied todetermine the energy gap within the plasmon pole and the random phase approximations. Optical properties are investigatedto determine the dielectric constant and the Bethe–Salpeter theory is used to calculate the exciton binding energies. Zincblende and wurtzite phases are considered to calculate the bulk energy gaps, which are compared to the experimental values,finding good agreement. The 2D structure exhibits an energy gap larger than that of the bulk, indicating the effects ofreduction in dimensionality; these changes can be attributed to the dangling bonds that are present in the 2D layer.