Effect of annealing treatment on the structure and performance of transparent conductive AZO/Al2O3 bi-layer films

Transparent and conductive Al-doped zinc oxide (AZO) films have a wider band gap, good optoelectronic characteristics, inexpensive and nontoxicity, compared with indium tin oxide (ITO). In this study, AZO films are deposited onto Al2O3/glass using magnetron sputtering. After deposition, both conventional annealing (CA) and rapid thermal annealing (RTA) are used to obtain a high quality AZO/Al2O3/glass bi-layer. The XRD and TEM images show that the film has a poly-crystalline nature with a hexagonal wurtzite-type structure. As the annealing temperature is increased, the intensity of the (0 0 2) diffraction peak increases and there is decrease in the full width at half maximum, which indicates that the films undergo a thermally activated process of grain growth and exhibit improved crystallization. RTA produces a larger grain, a greater carrier concentration and better crystallinity than CA. After RTA at 500 °C, the AZO/Al2O3 bi-layer films result in the lowest electrical resistivity, the highest optical transmittance and a good figure of merit. The bi-layer films are subject to a pull-off adhesion strength test, which shows that have a superior peel off stress. The experimental results show that these AZO/Al2O3 bi-layer films have good optoelectronic performance and adhesive strength.