Band-gap narrowing of titanium dioxide by nitrogen doping

TiO2-based powder, including 0.1 at% of N doped in the rutile lattice. has been synthesized by oxidation of TiN. As a result, a significant shift of the absorption edge to a lower energy in the visible-light region has been observed. The substitutional doping of N into the TiO2 lattice is found to be effective; its 2p states contribute to the band-gap narrowing by mixing with O 2p as shown in ab initio electronic structure calculations.