N-doping-related room temperature ferromagnetism of electrodeposited ZnCoO films

A series of Co-doped ZnO films were fabricated by an electrodeposition method. The X-ray diffraction results and absorption spectra show Co ions have been doped successfully into the ZnO crystal lattices. The as-grown samples have no ferromagnetism at room temperature. However, after plasma treatment used ammonia as reactive gas, the room temperature ferromagnetism was detected in ZnCoO samples. The Hall measurement reveals the resistivity of samples was increased by two orders of magnitude after the treatment. Although the aspect conductivity is an n type, some holes generated by N doping still play an important role to induce the room temperature ferromagnetic properties for Co-doped ZnO samples.