A combination of solution synthesis & solution combustion synthesis for highly conducting and transparent Aluminum Zinc Oxide thin films

Aluminum Zinc Oxide has been extensively investigated as a cheap alternative to transparent conducting tin oxide films for electronic and optoelectronic applications. Thin films of Aluminum Zinc Oxide have been developed successfully through a combination of solution combustion synthesis and solution synthesis. Zn(NO₃)₃·6H₂O as metal source was dissolved in 2-methoxyethanol as solvent through combustion synthesis with Urea as fuel while dopant source of AlCl₃·6H₂O was mixed separately in solvent to avoid aluminum oxide formation in the films. Precursor solutions were obtained mixing Zn & Al separate solutions in 9:1, 8:2, and 7:3 ratios respectively with oxide, fuel and dopant concentrations of 0.5, 0.25, 0.1, and 0.05 M. The film stacks have been prepared through spin-coating with heating at 400°C for 10 minutes after each deposition to remove residuals and evaporate solvents. Thermal annealing in oven at 600°C for 1 hour followed by rapid thermal annealing at 500°C & 600°C first in vacuum and then in N2-5%H2 environment respectively for 10 minutes each reduced the resistivity of film stacks. Film stack with 10 layers for an average thickness of 0.5μm gave the best Hall Effect resistivity of 3.2 × 10^-2 Ω-cm in the case of 0.5M solution with Zn:Al mixing ratio of 9:1 for RTA annealings at 600°C with an average total transparency of 80 % in the wavelength range of 400-1200 nm. The results show a clear trend that increasing the amount of ingredients resistivity could further be decreased.