The effect of Al3+ co-doping on the structural, magnetic and optical properties of ZnCoO thin films

Zn0.99−xCo0.01AlxO (x=0, 0.005, 0.01, 0.02) thin films have been prepared by a sol-gel method. The structural, optical and magnetic properties of the samples were investigated. X-ray diffraction, X-ray photoelectron and UV absorption spectroscopy analyses indicate that Al3+ and Co2+ substitute Zn2+ without changing the wurtzite structure. The (Al, Co) co-doped samples are ferromagnetic at room temperature, and the ferromagnetic moment increased with increasing concentration of Al3+. It was demonstrated experimentally that high-temperature ferromagnetism in Co-doped ZnO thin films can be obtained through increasing the carrier concentration, which was realized by doping a few percent of Al ions using a simple fabrication method.