Cobalt substituted ZnO thin films: a potential candidate for spintronics

Cobalt doped zinc oxide thin films have been deposited using spray pyrolysis method. These single phasic films exhibited [100] preferential texture and small decrease in the lattice parameter on cobalt substitution. The films having different Co concentration have almost similar surface morphology and microstructure. These Zn1-xCoxO (x <= 0.10) thin films distinctly showed ferromagnetic character at room temperature. The optical transmission measurements of these films clearly proved that in these films Co substitutes for Zn2+ and exists in +2 state. Based on the optical, structural and magnetic measurements, the possibility of occurrence of ferromagnetic ordering due to cobalt clustering is ruled out in these spray-pyrolyzed films. A correlation of the observed ferromagnetic behavior in these Zn1-xCoxO films with structural change resulting from the addition of Co is presented in this paper.