Synthesis and characterization of highly preferred orientation polycrystalline Co-doped ZnO thin films prepared by improved sol-gel method

Highly preferred orientation polycrystalline Zn_1-xCo _xO (x = 0, 0.03, 0.06, 0.09) thin films were prepared by improved sol-gel method on quartz glass substrates. The structural, optical and magnetic properties were investigated. The X-ray diffraction patterns show that all the samples have the same structure with one highly oriented c-axis (002) peak. None of the samples showed any signal of impurity phases. The c-axis lattice constant increased linearly with the increase in Co doping content, indicating that the doping of Co ions into the host lattice did not change the wurtzite structure of ZnO. UV-Vis transmittance spectroscopy showed that the average optical transmittance of the films is about 90 % in visible wavelength range. The optical band gap (Eg) decreased with increasing Co content. Also, the results of vibration sample magnetization ascertained the ferromagnetic behavior of Co-doped ZnO, having a Curie temperature higher than room temperature.