INVESTIGATION OF STRUCTURAL, OPTICAL, AND ELECTRICAL PROPERTIES OF ZnO THIN FILMS FOR ELECTRO-OPTICAL DEVICES

ZnO thin films were successfully deposited on fluorine-doped tin oxide substrates using a two-electrode homemade electrochemical deposition system. First, a zinc metal layer was deposited on the substrate via an electrochemical process, from aqueous solutions of zinc nitrate for various deposition times. Afterward, the Zn metal layer was transformed into multiple ZnO thin films through thermal oxidation under ambient air. Finally, a post-treatment was performed on the ZnO thin films by calcination. The morphology of the ZnO thin films, when observed under a scanning electron microscope, exhibited rough surfaces and porous characteristics. The X-ray diffraction patterns and the Raman shifts indicated hexagonal wurtzite structures. Moreover, the Fourier -transform infrared spectroscopy results confirmed the chemical structure of the films to be ZnO without a residue. The average optical transmittance values in the visible region were greater than 80%. The band gap energy was in the range of 3.13 to 3.43 eV. The four-point probe measurement revealed various sheet resistance values in the range of 167.21 to 1,066.28 omega/sq. Concerning the electro-optical property evaluation, the optical transmittance and sheet resistance values were considered for calculating the figure of merit. It was found that the highest value reached 3.08x10(-3) omega(-1), indicating that ZnO thin films have a potential application in electro-optical devices.