Photoluminescence properties of Co~(2+) -doped ZnO nanocrystals

摘要

We performed photoluminescence experiments on colloidal, Co~(2+)-doped ZnO nanocrystals in order to study the electronic properties of Co~(2+) in a ZnO host. Room temperature measurements showed, next to the ZnO exciton and trap emission, an additional emission related to the Co~(2+) dopant. The spectral position and width of this emission does not depend on particle size or Co~(2+) concentration. At 8K, a series of ZnO bulk phonon replicas appear on the Co~(2+) -emission band. We conclude that Co~(2+) ions are strongly localized in the ZnO host, making the formation of a Co~(2+) d-band unlikely. Magnetic measurements revealed a paramagnetic behaviour.