Effect of post annealing on the properties of aluminium doped Zinc oxide thin films deposited by DC sputtering

Abstract

Deposition of highly conductive and transparent ZnO:Al (AZO) thin films on glass substrates were done by direct current (DC) magnetron sputtering using ZnO:Al (2 wt%, Al2O3) target. Post deposition, annealing was done under oxygen (O2) and nitrogen (N2) environment at 200 °C, 300 °C and 400 °C. Structural, optical and electrical properties of the as-deposited and the annealed samples were studied by various techniques. Obtained results showed that the properties of the AZO thin films varied with the change in annealing environment and the annealing temperature. The crystallinity of the AZO thin films increased with the increase in temperature, when annealed in nitrogen atmosphere while a decrease in the compressive stress is observed. But in presence of oxygen environment, initially, the crystallinity decreased for 200 °C and thereafter increased with the increase in temperature. Elemental composition of the films was modified with the variation of annealing temperature and environment. The % transmittances of the annealed AZO films were in the range of 70% and above in the visible region. Electrical properties show that the carrier concentration, mobility and the resistivity of the films were influenced by the annealing conditions.