Influence of p-type and n-type dopants on the magnetic properties of ZnCuO based diluted magnetic semiconductor thin films

Cu-doped ZnO (ZnCuO), Cu-Ga co-doped ZnO (Zn(Cu, Ga)O) and Cu-Na co-doped ZnO (Zn(Cu, Na)O) diluted magnetic semiconductor thin films have been deposited on (0001) sapphire substrates by pulsed laser deposition. All the films have a hexagonal wurtzite ZnO structure with a high c-axis orientation. Hall-effect measurements showed that the ZnCuO film is n-type, in which the carrier concentration is greatly enhanced by the addition of Ga, while the introduction of Na resulted in p-type behaviour with a high resistivity. The magnetic hysteresis measurement indicated that the pure ZnCuO film is ferromagnetic at room temperature. Doping of Ga (n-type dopant) does not have a significant effect on the room temperature ferromagnetism. However, the room temperature ferromagnetic behaviour is destroyed by the addition of Na (p-type dopant). X-ray photoelectron spectroscopy analyses revealed that there exist more oxygen defects in the ZnCuO, Zn(Cu, Ga)O films than in the Zn(Cu, Na) O film. It was suggested that the interaction of Cu2+ with the oxygen defect in an n-type environment is responsible for the ferromagnetism observed in the ZnCuO system.