Amplification of the UV Emission of ZnO: Al Thin Films Prepared by Sol-Gel Method

Pure ZnO and Al doped ZnO (1%) thin films were prepared by sol-gel process using zinc acetate, ethanol, diethanolamine (DEA) and aluminum nitrate, respectively, as precursor, solvent, catalyst and source of the doping element. The films deposition was carried out at room temperature by dip-coating technique on glass substrates. The obtained samples were dried at 200 ° C for 40 min and then annealed at 500 ° C for one hour. The X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmittance spectrophotometry and luminescence spectroscopy (PL) were used for the samples characterization. XRD results showed that ZnO nanocrystallites phase had a wurtzite structure with a preferred orientation along c-axis. The SEM micrographs revealed a homogeneous ZnO cristallittes dispersion within the layer. The optical transmittance spectra showed that the Al presence improves the optical transmittance in the visible. The room temperature UV photoluminescence revealed that the ZnO: Al (1%) emission intensity is three times greater than that of pure ZnO. In addition, the Al doped ZnO emission is shifted to larger energies of 0.2 eV relative to that of pure ZnO. These results show that the doping of ZnO with a proportion of 1% aluminum is of great importance for applications in optics and optoelectronics.