The Effect of Substrate Temperature on the Room Temperature Ferromagnetism of Co-Doped ZnO Thin Films

Zn1-xCoxO (x=0.08-0.31) thin films were prepared on c-cut sapphire substrates by magnetron co-sputtering. The effects of substrate temperatures on the structures and magnetic properties of Co-doping ZnO thin films were investigated. The results indicate that c-cut sapphire substrates induce highly (002) oriented growth of ZnCoO films. And all films show room temperature ferromagnetism. Moreover, the low substrate temperature can not only hinder the generation of the second Co2O3 phase, but also remarkably enhance the ferromagnetism of ZnCoO film compared with high substrate temperature. Optical spectrometry indicates that Co2+enters the tetrahedral sites of the wurtzite structure of ZnO host and substitutes for Zn2+.