Structural and photoluminescence properties of Al-doped zinc oxide nanoparticles synthesized in polyol

Abstract

Al-doped ZnO (AZO) nanoparticles have been prepared using a modified polyol process that makes use of di-ethylene glycol as a solvent. This procedure allows for obtaining nanoparticles with a narrowed size distribution, a controlled morphology and a high crystal quality. The prepared AZO nanoparticles were annealed at 400°C. We studied the effect of doping and annealing on structural and optical properties. The structural investigations of the products confirmed the hexagonal wurtzite structure for all products and having a most preferred orientation along (101) plane. The results obtained by TEM revealed that the average particle size of the products decreases by doping and increases by annealing temperature. Energy dispersive spectroscopy (EDS) confirms the substitution of Al into ZnO lattice. Raman scattering analysis shows that the crystallinity of the material was improved by increasing the concentration of the dopant Al3+ and the photoluminescence spectra shows that the UV emission peak position of AZO nanoparticles exhibited a slight blue shift from 384 to 383nm, and the intensity decreased with increasing the Al concentration, which is attributed to an increase in nonradiative recombination. However the UV emission peak position of AZO (0.2% and 0.6%) nanoparticles annealed at 400°C exhibited a slight red shift due to the influence of the size effect on the energy level of confined excitons, because of the average size of the nanoparticles obviously became bigger with the increase of annealing temperature.