A hybrid density functional study on the electron and hole trap states in anatase titanium dioxide

Abstract

We present a theoretical study on electron and hole trap states in the bulk and (001) surface of anatase titanium dioxide using screened hybrid density functional calculations. In both the bulk and surface, calculations suggest that the neutral and ionized oxygen vacancies are possible electron traps. The doubly ionized oxygen vacancy is the most stable in the bulk, and is a candidate for a shallow donor in colorless anatase crystals. The hole trap states are localized at oxygen anions in both the bulk and surface. The self-trapped electron centered at a titanium cation cannot be produced in the bulk, but can be formed at the surface. The electron trap level at the surface oxygen vacancy is consistent with observations by photoelectron spectroscopy. The optical absorptions and luminescence in UV-irradiated anatase nanoparticles are found to come from the surface self-trapped hole and the surface oxygen vacancy.

The Effect of Acceptor and Donor Doping on Oxygen Vacancy Concentrations in Lead Zirconate Titanate (PZT)

“…A further possible intrinsic trap is an oxide ion that might form O − or superoxide ions. Such a hole trap was suggested for TiO 2 [66] but might be rather shallow. Pb 2+ /Pb 3+ may also act as a neutral hole trap and the existence of Pb 3+ is indeed discussed in the literature, but this trap is assumed to be shallow [67,68,69].…”

Quasiparticle Band Structures of Defects in Anatase TiO2 Bulk

“…4(e)) with the excess electrons trapped at the vacancy site. This kind of state is also called small polaron which has attracted great attention in the community of TiO 2 [14,16,[29][30][31][32][33][34]. This defect state is 1.0 eV below CBM and 1.9 eV above VBM in LDA+U .…”

Single oxygen vacancies of (TiO2)35as a prototype reduced nanoparticle: implication for photocatalytic activity

“…For comparison, the calculated energy values of bulk anatase TiO 2 are given in Table S1. 28,34,39,66 Actually, ∆ H-L is only an approximation to the band gap and the quality of approximation is determined by the calculation methods. 54 In the case of DFT, it depends on the exchange-correlation potential and the ratio of HF in functional.…”