Structural, optical and magnetic properties of Zn1-xCoxO thin films prepared by spray pyrolysis

A series of Co-doped ZnO films were fabricated by a spray pyrolysis method. The X-ray diffraction patterns of the films showed that the undoped and Co-doped ZnO films exhibit wurtzite crystal structure. Surface morphology of the films obtained by scanning electron microscopy reveals that pure ZnO film has the hexagonal shaped microrods. The introduction of Co content in the structure did not affect the surface morphology of the films significantly. Magnetic hysteresis loops were observed at room temperature, indicating that ferromagnetism can be realized with Co doping into ZnO. The values of remnant magnetization and coercive field slightly decreased when the concentration of Co was increased beyond 1 at.%. The calculated band gap value of undoped and 1 at.% Co doped samples was found to be around 3.08 eV. The band gap energy increases upon 3 at.% Co concentration followed by a decrease for further increase in Co concentration toward 5 at.%