Transparent and Conductive Al-Doped ZnO Thin Films. Influence of Al Concentration

Aluminum doped zinc oxide thin films, AZO, onto soda-lime glass substrates by the ultrasonic spray pyrolysis (USP) were deposited. The molar concentration of the starting solution, temperature and time deposition were kept constant at 0.2M, 450°C and 6.5min, respectively. The Al concentrations in the starting solutions were varied at values of 1, 2, 3 and 5 at%. In this work, the structural, morphological, optical and electrical properties of AZO thin films were analyzed by using X-ray diffraction, XRD, scanning electron microscopy (SEM), UV-Vis spectroscopy, sheet resistance and Hall effect measurements, respectively. In all samples, the preferential growth in the [002] direction was observed. The average optical transmission in the UV-Vis region of AZO films presented high optical transparencies, >80%. The energy bandgap values varied around of 3.3eV, and the maximum figure of merit was of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.86 \times 10^{-3}(\Omega / \square)^{-1}$</tex>. These properties make the AZO films applicable as transparent electrodes.