Electronic Structure of ZnS Crystal Doped with One or Two Transition Metal Atoms (Cr, Fe)

The electronic and magnetic properties of ZnS crystal with impurities of transition 3d elements Cr and Fe, which replace Zn atoms, are calculated. The calculations are performed in 2×2×2 sphalerite supercells containing 64 atoms. The same supercells, which contain both Cr and Fe impurities, are also considered. It is established that energies of 3d electrons of the Cr atom with spin up in the Zn31Cr1S32 supercell are localized in narrow energy intervals around the Fermi level and at the top of the valence band. For spin-down states, this material exhibits the properties of a semiconductor with a direct band gap of 2.11 eV. The magnetic moment of the supercell equals to 4 μB. The results of the calculation for the Zn31Fe1S32 supercell show that this material is a direct-band semiconductor with the width of the band gap at the Γ point of about 1.96 eV. 3d electrons with spin down are localized in narrow energy bands near the Fermi level and at the bottom of the conduction band. The pseudogap value for electrons with spin down is 0.53 eV. The magnetic moment of the supercell is also equal to 4 B. It is found from the results of the calculation for the Zn30Cr1Fe1S32 supercell that 3d electrons of the Cr atom with spin up are localized in the vicinity of the top of the valence band and the Fermi level, which is inside the valence band. The optical gap at the Γ point is equal to 0.60 eV and the indirect fundamental gap (Γ – R) is 0.59 eV. The pseudogap value for electrons with spin down is 0.60 eV. The magnetic moment of the supercell equals 8.04 μB. The calculations are performed using the ABINIT program. The hybrid exchange-correlation functional PBE0 is used to eliminate the self-interaction error of Cr and Fe 3d electrons.