First-principles studies of electronic structure, magnetic and optical properties of rare-earth (RE= Sm, Eu, Gd, and Er) doped ZnS

We present a theoretical study of the electronic structure, magnetic and optical properties of RE-doped zinc sulphide (RE = Sm, Eu, Gd, and Er) in a zinc blende phase, which is investigated using the spin-polarized spin density functional theory (spin-DFT). The First-principles calculations based on density functional theory and the full-potential linearized augmented plane wave method (FP-LAPW) are performed by employing the GGA + U (U is the Hubbard term of the Coulomb repulsion correlation) approximation. The lattice parameter will increase by RE doping ZnS. The total density of states (TDOS) and partial density of states (PDOS) show that all the systems have half-metallic character behaviour with 100% spin polarization at the Fermi level provided by the RE-4f states except ZnS: Eu it has a semiconductor character. The values of differences in total energy AE indicate that ZnS: Sm, ZnS: Eu, and ZnS: Er are stable in the ferromagnetic phase. However, ZnS: Gd favours the AFM phase. The total magnetic moment of all systems is very interesting. All systems showed significant redshift except ZnS: Eu, and all exhibited broad absorption in the UV region. Doping by RE is a feasible method to enhance the electronic, magnetic, and optical properties of ZnS for the new generation of optoelectronic and spintronic applications.