Ab initio calculations for studying electronic band structure of ideal and defective Cd 1 -x Mn x Se (0.01 ≤ х ≤ 0.07) semimagnetic semiconductors have been performed. It has been defined that with an increase in concentration of Mn in Cd 1 -x Mn x Se compound, there is a decrease in the band gap. Based on the results obtained we can conclude that ferromagnetic phase is more stable than antiferromagnetic one. It has been found that defects such as vacancy, interstitial atom, and Frenkel pair lead to an increase in the band gap, change in the total energy, and formation of local levels in the band gap.

This work is devoted to theoretical investigations of Cd1-xMnxS semimagnetic semiconductors (SMSC). The purpose of this work was to calculate the electronic band structure of ideal and defective Cd1- xMnxS SMSC in both antiferromagnetic (AFM) and ferromagnetic (FM) phases. Ab initio, calculations are performed in the Atomistix Toolkit (ATK) program within the Density Functional Theory (DFT) and Local Spin Density Approximation (LSDA) on Double Zeta Double Polarized (DZDP) basis. We have used Hubbard U potential UMn = 3.59 eV for 3d states for Mn atoms. Supercells of 8 and 64 atoms were constructed. After the construction of Cd1-xMnxS (x = 6.25 %; 25 %) supercells and atom relaxation and optimization of the crystal structure were carried out. Electronic band structure and density of states were calculated, the total energy has been defined in antiferromagnetic (AFM) and ferromagnetic (FM) phases. Our calculations show that the band gap increases with the increase in Mn ion concentration. It has been established that Cd or S vacancy in the crystal structure leads to the change of band gap, Fermi level shifts towards the valence or conduction band.

No abstract

The transmission spectra of γ-irradiated Cd1-xFexS (x=0.05) thin films were carried out to study the effect of γ-irradiation upon optical properties and dispersion parameters. It was found that the optical properties of Cd1-xFexS thin films were highly affected by the exposure to γ-irradiation. The optical absorption spectra showed that the absorption mechanism is a direct allowed transition. The optical energy gap increases with the increase in irradiation dose. The values of optical constants were affected obviously with the increase in irradiation dose.