Effect of Mg,Sn Co-doping on the Photoelectric Properties of ZnO Thin Films

The ZnO thin films doped with different Mg,Sn were synthesized on quartz glass substrate by sol-gel spin coating method. The effects of Mg,Sn Co-doping on microstructure,surface morphology and photoelectric properties were characterized by X-ray diffraction,scanning electron microscopy,ultraviolet visible(UV-Vis) and four point probe,and the inner mechanism were also explored. The results show that the films still remain hexagonal wurtzite-structured with c-axis preferred orientation growth after doped Mg and Sn. The grain size will increase a little after doped 2% Mg,kept Mg 2at% unchanged,doping Sn,the compactness,flatness and grain uniformity of the film will be improved obviously although the grain size will decrease. The band gap will be broadened for Quantum Confinement effect caused by the decrease of grain size and the Burstein-Moss effects caused by the increased carriers,which were provided by the metallicity difference between Mg ion and Zn ion,and Sn ion substitute for Zn ion in lattice. In the same time,the transmittance in visible region will also be improved after doping Mg and Sn. The electrical resistivity will drop sharply for the increasing of carrier concentration and improving of mobility for the better crystalline quality after doped Mg and Sn.