Structural, Electrical and Optical Properties of ZnO Films Deposited by Ultrasonic Chemical Spraying for Application as Transparent Conductors

Zinc oxide (ZnO) thin films were fabricated on glass substrates using the ultrasonic chemical spray method, USP. Initial solutions were prepared from milled precursors. The milling process of the precursors was carried out using a planetary ball mill at constant speed, 300 rpm, and different times:15, 30, 45, 60 and 120 minutes. The ZnO films were manufacture data constant deposition temperature of 475 °C and two different deposition times: 8 and 14 min. X-ray diffraction analysis confirmed that all spectra of the films match well with the hexagonal wurtzite structure, exhibiting a preferential orientation along the (002) planes. Characterization of the surface morphology by scanning electron microscopy (SEM) revealed changes in morphology with the milling process. The optical analysis, transparency and band gap values, was obtained from the optical transmission spectra. The electrical characterization indicate that, under identical deposition conditions, the electrical properties of ZnO thin films fabricated from milled precursors are superior to those obtained from initial solutions prepared with unmilled precursors. Therefore, the use of milled precursors for the deposition of ZnO thin films by ultrasonic chemical spraying has a significant impact on their physical properties, which is associated to the chemical transformation of the precursor salts during the milling due to the high energy processes presented.