Optical and magnetic properties of Zn0.9−xCo0.1O : Alx thin films

The high-Tc ferromagnetic property in Co-doped ZnO (ZCO), mediated by donor impurity band was tested by controlled introduction of shallow donors (Al) in the Zn0.9−xCo0.1O:Alx (x=0.005 and 0.01) thin films. The saturation magnetization for the 10% Co-doped ZnO (4 emu/cc) at 300 K reduces (∼0.8 emu/cc) due to Al doping. The resistivity drops abruptly, from ∼103Ω-cm for the ZCO film to 0.033 and 0.02Ωcm for the 0.5% and 1.0% Al doped ZCO samples, respectively. The XPS measurements did not show any signature of metallic Co clusters formation in these samples.