The diffusion behaviors of Co clusters on clean ZnO(00•1)-Zn single crystal surface and their magnetic properties were studied. Co clusters were deposited on the clean ZnO(00•1)-Zn surface at room temperature and then undergone ultra-high vacuum annealing until fully reconstructed. The replacement of Zn2+ by Co2+ was confirmed by scanning tunnelling microscopy and X-ray photo-electron spectroscopy. The Co-doped ZnO showed a weak ferromagnetism at room temperature with a saturation magnetic moment of 1.08μB/Co. The observations indicated that surface Zn vacancies facilitated Co diffusion, and the interplay of Co ion with internal O vacancies led to the ferromagnetism.

Co Doped ZnO(0001)-Zn by Diffusion Method and its Magnetic Properties. Xie, W.G., Xie, F.Y., Yu, X.L., Xue, K., Xu, J.B., Chen, J., Zhang, R.: Applied Physics Letters, 2009, 95[26], 262506