Film thickness effect on structural, optical and electrical properties of indium oxide (In2O3) thin films grown via sol-gel method

In this work, we investigated the effect of the thickness on structural, morphological, optical, and electrical properties of In2O3 thin films synthesized via by sol–gel spin coating technique. The prepared samples were characterized by various techniques including X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray (EDX) spectra, UV-Vis-NIR spectrophotometer as well as the electrical measurements via the four-probe technique. The XRD analysis reveals that the films have a cubic crystalline structure, with (222) preferential orientation. The crystallite size values of the films were varied from 14 to 27 nm. The (SEM) images indicated that the homogenous and smooth surface with better adherent to the substrate surface. The EDX spectrum reveals the presence of In and O element necessary for In2O3 films for film formation. Excess of oxygen is observed due to the substrate contribution. The transmittance results exhibit that the films are highly transparent, more than 75% in the visible range from 400 nm to 800 nm is measured. The estimated band gap energy is found to increase with increasing film thickness (3.37–3.7 eV). The electrical resistivity of the In2O3 thin films substantially decreases with the increasing film thickness from 1.48×10 - 4 to 1.3×10 - 3 Ω.cm.