Localized states induced by an oxygen vacancy in rutile TiO2

Abstract

Using density functional theory and model Hamiltonian analysis, we investigate the localized states induced by an oxygen vacancy in rutile TiO 2 . We identify two classes of localized states-the hybrid and the polaron. The hybrid state is caused by the orbital overlap between three Ti atoms next to a vacancy and is mainly derived from the Ti e g orbitals. The polaron state is caused by the local lattice distortion and is mainly composed of one particular t 2g orbital from a single Ti atom. The first principles calculation shows that the polaron state is energetically favored, and the tight-binding analysis reveals the underlying connection between the bulk band structure and the orbital character of the polaron. The magnetic coupling between two nearby polaron states is found to be ferromagnetic. Using this picture, we analyze the results of recent theoretical calculations and experiments and discuss the connection to vacancies in SrTiO 3 . V C 2015 AIP Publishing LLC. [http://dx.

Oxygen-vacancy driven electron localization and itinerancy in rutile-based TiO2

“…These findings are indeed reminiscent of the identification of different V O charging states in DFT+U and/or DFT hybrid-functional studies. 18,22,24 Also the characterization of two different site-orbital levels has been reported before, yet usually by invoking explicit magnetic ordering. Our two detected charging states with n can VO = 1.89, reading V 65 An established theoretical picture 18 describes the vacancy-defect state as a bound object consisting of V 2+ O plus two polarons, rendering it charge neutral again.…”

Synthesis, properties, and applications of black titanium dioxide nanomaterials

“…In addition, coupling with small-gap semiconductors (such as CdS and ZnO) or graphene have also been tried [58][59][60][61][62][63][64][65][66][67][68][69]. Oxygen vacancies and Ti 3+ can also been shown with visible-light activity [68,[70][71][72][73][74][75][76][77][78][79][80][81][82][83]. Feng and Huang's group [71,73,[78][79][80][81][82][83] prepared several Ti 3+ self-doped TiO 2 nanomaterials with enhanced photocatalytic activities in hydrogen generation and wastewater degradation.…”

Epitaxial integration of TiO2 with Si(100) through a novel approach of oxidation of TiN/Si(100) epitaxial heterostructure

“…Polaron state stems from local lattice distortion which lower the energy of Ti local orbitals, while hybrid state originates from orbital overlapping among three Ti atoms. These models have been proposed theoretically [25,26]. The other mechanism proposed for the source of magnetism is related to the presence of Ti vacancy and dioxygen molecule in the system which has been shown theoretically, as well [27].…”