An investigation of the role of transition metal ions impurities in CdO: Local structure and electronic properties

According to the high-order perturbation formulae of 3d5 (Mn2+ ) and 3d9 (Cu2+ ) ions in octahedron, the local structures and electron paramagnetic resonance (EPR) parameters (g factors and hyperfine structure constants A) for Cu2+ and Mn2+ in CdO are theoretically studied in a consistent way. Due to the Jahn-Teller effect, both the substituted sites of Cu2+ and Mn2+ show the tetragonally elongated distortion with different elongation τ. Meanwhile, the crystal field and covalency around doped Cu2+ and Mn2+ are obtained, which can account for the electronic properties in doped CdO. In order to make further investigation of the potential optical and electrical properties, the band structure and density of states (DOS) of pure and transition metal ions (TMs) doped CdO are comparably calculated through density functional theory (DFT). The results show that the band gap of Mn2+ - and Cu2+ -doped CdO can be effectively reduced, due to the improved covalency between the central ions and ligand ions.