Effect of oxygen vacancies on electronic structures and field emission properties of TiO_2 nanotubes: A density-functional theory investigation

摘要

Influence of oxygen vacancies (V_o's) on electronic structures and field emission properties of TiO_2 nanotubes (NTs) is investigated by first-principle calculations. It is demonstrated that the formation of 3-fold coordinated V_o gives rise to two shallow donor states below the conduction band minimum. Whereas one shallow coupled with another deep donor states appears in the case of a 2-fold bridging vacancy located on the outer side-wall of TiO_2 NT. V_o's are found to greatly reduce the barrier for electron extracting. These results can explain why, experimentally, TiO_2 NTs with intrinsic V_o can overcome the hieh barrier of electron affinitv and exhibit an excellent field-emission performance.