Observation of Room Ferromagnetism in Cu-Implanted Crystal ZnO

Ion implantation technique is used to study the magnetic properties of Cu-doped ZnO. The room temperature ferromagnetism in the Cu-implanted ZnO samples is observed. From the photoluminescence spectrum of implanted samples we observe a broad green emission around 510 nm, which is related to defects in the samples. X-ray photoelectron spectroscopy measurement shows that Cu ions are in the mixed oxidation state of +1 or +2 and substitute for the Zn²⁺ ions of the ZnO matrix. We argue that the ferromagnetism is related to these defects, and the substitution of Cu²⁺ into Zn²⁺ sites in crystal ZnO could contribute to the observed ferromagnetism.