Physical properties of IZO thin films deposited by ultrasonic spray pyrolysis. Effect of In concentration and precursor milling process.

Indium doped zinc oxide films, IZO, deposited onto soda-lime glass substrates by the ultrasonic spray pyrolysis, USP, were prepared from milled Zn precursor. The influence of the In content (at%) in the starting solution and grinding process was analyzed. 0.2 M starting solutions with different In concentrations, 1, 2, and 3 at% were prepared. The deposition conditions were kept constant, substrate temperature of 450°C, and a deposition time of 7 min. The milling process was carried out in a planetary ball mill, with a ball/powder ratio of 4:1, and a speed of 300 RPM.The structural, morphological, optical and electrical properties of the ZO and IZO were analyzed by X-ray diffraction, XRD, field emission scanning electron microscopy, FESEM, UV-Vis spectroscopy, and sheet resistance and Hall effect measurements, respectively.From XRD analysis was found that both ZO and IZO films present a preferential orientation along the (002) planes. The FESEM images confirm that all deposited films present hexagonal nanostructures with different size. The average optical transmission oscillated in the range of 82-87%, confirming the high transparency of all the deposited films. The lowest resistivity value, 3.72 × 10 ^–3 Ωcm, was obtained in the 3 at% film (3IZO-M) and a figure of merit of 3.22 × 10 ^–3 ( ^Ω / square ) ^–1 . According to the obtained results, it can be stated that IZO films deposited by the USP technique, are potentially applicable in the optoelectronics field.