Functional complex point-defect structure in a huge-size-mismatch system.

Cubic boron nitride is a promising system for photonics and optoelectronics. Determining the inclusion mechanisms for dopants with a large size mismatch, such as luminous rare-earth elements, is prerequisite to understanding their functional properties and to effective doping control. Combining evidence from subangstrom resolution scanning transmission electron microscopy, imaging simulations, and first-principles calculations, we show that cationic Ce(3+) single dopants are not located at cationic B sites but rather at anionic N sites surrounded by B-site vacancies.