Intrinsic defect in BiNbO4: A density functional theory study

Formation energies, transition energy levels, and electronic properties of various intrinsic defects in BiNbO4 systems are studied based on the first-principles density-functional theory. Our results indicate that the acceptor defects form easier than donor defects under O rich condition, while it is opposite under Bi rich condition. Under O-rich condition, Bi vacancies (Bi-vac) leading to p-type conductivity are the dominant intrinsic defects, whereas O vacancies (O-vac) inducing moderate n-type conductivity are the dominant intrinsic defects under Bi-rich condition. Among these intrinsic defects, O-vac is a deep donor; to the contrary, Bi-vac is found to be a shallow acceptor which is benefit to the separation and migration of the photogenerated carriers. Consequently, the BiNbO4 with Bi-vac under O-rich growth condition should be of better photocatalytic performance. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4747919]