Band gap narrowing of titanium dioxide by sulfur doping

TLDR

Titanium dioxide was doped with sulfur by oxidation annealing of TiS₂, and ab initio band calculations revealed that mixing of S 3p states with the valence band contributes to band‑gap narrowing. X‑ray diffraction shows TiS₂ converts to anatase TiO₂ at 600 °C, residual S occupies O sites forming Ti–S bonds, shifting the absorption edge to lower energy, and ab initio calculations attribute the band‑gap narrowing to mixing of S 3p states with the valence band.

Abstract

Titanium dioxide (TiO2) doped with sulfur (S) was synthesized by oxidation annealing of titanium disulfide (TiS2). According to the x-ray diffraction patterns, TiS2 turned into anatase TiO2 when annealed at 600 °C. The residual S atoms occupied O-atom sites in TiO2 to form Ti–S bonds. The S doping caused the absorption edge of TiO2 to be shifted into the lower-energy region. Based on the theoretical analyses using ab initio band calculations, mixing of the S 3p states with the valence band was found to contribute to the band gap narrowing.