Preparation and conductivity enhancement of Al-doped zinc oxide thin films containing trace Ag nanoparticles by the sol-gel process

Al-doped zinc oxide (AZO) thin films containing trace Ag nanoparticles (Ag/Zn = 0-0.15 at.%) were prepared by the sol-gel process. It was found that the doping of Ag nanoparticles resulted in the significant sintering of AZO grains and further led to the enhancement of conductivity. From the analysis of surface morphology, it was suggested that the presence of Ag nanoparticles might be helpful for the sintering of AZO grains at lower temperatures, which increased the grain size (or decreased the grain boundaries) and led to the decrease in electrical resistivity. By optimizing the heat treatment conditions, the electrical resistivity of AZO thin films containing 0.1 at.% Ag could be lowered to be 1.72 × 10^-3 Ω cm when the calcination temperature was 550°C and hydrogen treatment was conducted in the Ar/H ₂ (97/3) atmosphere at 500°C and at a gauge pressure of 0.4 kg cm^-2. In addition, the optical transmittances of AZO thin films containing Ag nanoparticles were higher than 85% in the visible wavelength region. The decrease in transparency owing to the surface plasmon resonance of Ag nanoparticles was negligible.