First-principles study of Si and O co-doped band gap opening of TiN

Experimental observations suggest that Si doping could induce semiconducting behavior in metallic TiN. We present here results of density functional theory based calculations of the band structure for the TiN with homogeneous doping using Si dopant (Ti is substituted by Si) and O dopant (N is substituted by O or O atoms are at the interstitial positions) to explain the above metal-insulator transition. We find that 12.5% Si dopant together with O atoms at the interstitial sites () induces a semiconducting character. In this structure, 12.5% Ti atoms are substituted by Si and that there are two types of interstitial O atoms: one forming Si-O bond and the other not. The indirect band gap is calculated to be about 0.5 eV. Our results show that the co-effect of interstitial O and Si dopants plays an important role in inducing metal to semiconductor behavior of TiN.