Effects of cobalt doping concentration on properties of zinc oxide films prepared by sol-gel

The cobalt doped zinc oxide thin films were synthesised on quartz glass substrates by sol-gel method. Through the analysis of XRD, FTIR, SEM, two dimensional Fourier transform and UV-VIS, it shows that, as the cobalt doping concentrations are less than 2 at%, the films have the c-axis preferred orientation with hexagonal wurtzite structure, smooth surface, compact structure and the average transmittance are more than 87% in the visible region. The photoluminescence (PL) emission spectra indicates the Blu-ray peaks move to the direction of long-wave band by cobalt doping; the research also shows that, with the further increasing of the cobalt doping concentration, the (002) of XRD peak and the intensity of PL gradually disappear, the films no longer have typical hexagonal wurtzite structure, meanwhile, SEM and two dimensional Fourier transform images indicate the surface of films become rougher, moreover, the optical band gap and the optical transmittance in the ultraviolet band significantly become smaller.