Observation of the defect states in individual Co-doped ZnO dilute magnetic semiconducting nanostructures by electron energy-loss spectroscopy

Defects play a crucial role in room temperature ferromagnetism of dilute magnetic semiconductors. Using valence electron energy-loss spectroscopy (EELS), it was found that the band gap of Co-doped ZnO was smaller than undoped ZnO and some midgap states appeared. Using core-loss EELS, the fine structures of the O K-edge exhibit material-specific defect features in the oxygen spectra. The EELS measurements with super high spatial resolution provide unambiguous indications that defects are presented in Co-doped ZnO nanostructures.