Band-Gap Narrowing of Titanium Dioxide by Nitrogen Doping

TiO 2 -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 TiO 2 lattice is found to be effective; its 2 p states contribute to the band-gap narrowing by mixing with O 2 p as shown in ab initio electronic structure calculations.