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[en] Magnetic, electronic and structural properties of titanium dioxide material with different structural defects are studied using the first-principles ab-initio calculations and the Korringa–Kohn–Rostoker method (KKR) combined with the coherent potential approximation (CPA) method in connection with the local density approximation (LDA). We investigated all structural defects in rutile TiO_2 such as Titanium interstitial (Ti_i), Titanium anti-sites (Ti_o), Titanium vacancies (V_T_i), Oxygen interstitial (O_i), Oxygen anti-sites (O_T_i) and oxygen vacancies (V_o). Mechanisms of hybridization and interaction between magnetic atoms are investigated. The transition temperature is computed using the Mean Field Approximation (MFA).Magnetic stability energy of ferromagnetic and disordered local moment states is calculated to determine the most stable state. Titanium anti-sites have a half-metallic aspect. We also studied the change type caused by structural defects in this material. - Highlights: • Green function technique is used to study disordered systems. • We used DFT to study electronic structure of TiO_2 perturbed by defects. • TiO_2 with titanium antisite defect posesses a magnetic behavior. • The transition temperature is computed using the Mean Field Approximation.
[en] First-principles density functional theory calculations were carried out to study the structural, electronic, optical and electrical properties of fluorine-doped zinc oxide in detail. Fluorine substitutions of the oxygen sites create shallow donors derived mainly from the orbital 2p of fluorine. Additionally, the calculated optical properties reveal that the energy band gap gradually expands when increasing the fluorine doping level, which leads to a blue-shift in the optical transparency. More interestingly, the electrical conductivity is significantly enhanced after fluorine doping. (paper)
[en] We discuss the fundamental transparent conducting properties of halogens doped SnO2 rutile systems include the structural, electronic structure, optical and electrical properties. Within this study, we employ the first-principles calculation of the full potential linearized augmented plane wave (FP-LAPW) method based on the density function theory and semiclassical Boltzmann equations. It is found that the halogens substitutional doping cause an expansion of SnO2 lattice constants and low thermodynamic perturbation. The dopants act as shallow donors by creating impurity states at the bottom of the conduction band that lead to blue-shift in the optical transparency. Moreover, the electrical conductivity of SnO2 Rutile is significantly improving by halogens doping. In fact, these results could stimulate the future experimental works for elaborating new generations of the transparent conducting oxides in an optimal way.
[en] Highlights: • The incorporation of Al in ZnO increases the optical band edge absorption. • Incorporated Al creates shallow donor states of Al-3s around Fermi level. • Transmittance decreases in the visible and IR regions, while it increases in the UV region. • Electrical conductivity increases and reaches almost the saturation for high concentration of Al. - Abstract: We report, in this work, a theoretical study on the electronic, optical and electrical properties of pure and Al doped ZnO with different concentrations. In fact, we investigate these properties using both First Principles calculations within TB-mBJ approximation and Boltzmann equations under the constant relaxation time approximation for charge carriers. It is found out that, the calculated lattice parameters and the optical band gap of pure ZnO are close to the experimental values and in a good agreement with the other theoretical studies. It is also observed that, the incorporations of Al in ZnO increase the optical band edge absorption which leads to a blue shift and no deep impurities levels are induced in the band gap as well. More precisely, these incorporations create shallow donor states around Fermi level in the conduction band minimum from mainly Al-3s orbital. Beside this, it is found that, the transmittance is decreased in the visible and IR regions, while it is significantly improved in UV region. Finally, our calculations show that the electrical conductivity is enhanced as a result of Al doping and it reaches almost the saturation for high concentration of Al. These features make Al doped ZnO a transparent conducting electrode for optoelectronic device applications