Electronic and optical properties of N-doped, Co-doped as well as N,Co-codoped rutile TiO2

Abstract

We have used the first-principles plane-wave pseudopotential calculations to study the electronic and optical properties of N-doped, Co-doped as well as N,Co-codoped rutile TiO2 crystals. Results show that N-doped rutile TiO2 exhibits a semiconducting characteristic with a stable antiferromagnetic ground state. Co-doped rutile TiO2 shows half-metallic ferromagnetism with a stable ferromagnetic ground state, indicating that this doped material is useful in spin injection applications. N,Co-codoped rutile TiO2 has a nearly half-metallic nature with a stable ferromagnetic ground state. In addition, the optical absorption spectrum shows that N-doped, Co-doped and N,Co-codoped rutile TiO2 all extend the optical absorption in the visible-light region, and especially, Co-doped rutile TiO2 has the best absorption character in the visible-light region. We also discuss the influence of Coulomb interactions of 3d electrons of Co and Ti on the electronic structure of the doped systems studied.