Interesting Magnetic and Optical Properties of ZnO Co-doped with Transition Metal and Carbon

Magnetic and optical properties of ZnO co-doped with transition metal and carbon have been investigated using density functional theory based on first-principles ultrasoft pseudopotential method. Upon co-doping with transition metal (TM) and carbon, the calculated results show a shift in the Fermi level and a remarkable change in the covalency of ZnO. Such cases energetically favor ferromagnetic semiconductor with high Curie temperature due to p-d exchange interaction between TM ions and holes induced by C doping. The total energy difference between the ferromagnetic and the antiferromagnetic configurations, spatial charge and spin density, which determine the magnetic ordering, were calculated in co-doped systems for further analysis of magnetic properties. It was also discovered that optical properties in the higher energy region remain relatively unchanged while those at the low energy region are changed after the co-doping. These changes of optical properties are qualitatively explained based on the calculated electronic structure. The validity of our calculation in comparison with other theoretical predictions will further motivate the experimental investigation of (TM, C) co-doped ZnO diluted magnetic semiconductors.