Development and characterization of transparent conductive oxide semiconductors via sol-gel dip coating method

Abstract

Within the scope of this study, it was aimed to efficiently produce transparent conductive nickel oxide (NiO) thin films by the sol-gel dip coating method and to examine the structural, electrical, optical and surface properties of the produced thin films. Then, it was focused on investigating the effect of electromagnetic radiation on these films. NiO solutions were synthesized using different stabilizers: diethanolamine (DEA) and monoethanolamine (MEA). The synthesized solutions were then coated on the substrate materials with 5, 10 and 15 layers by dip coating method, and annealing was carried out at 450°C for 1, 1.5, 2.5 and 3 hours. To observe the microstructural, morphological and optoelectronic properties of the produced films, X-ray diffraction, UV-Vis spectroscopy, Raman spectroscopy, Fourier Transform Infrared Spectroscopy, surface profilometry and contact angle values were measured and their properties were compared with the changes among themselves. Thin films were then exposed to gamma radiation to observe the effects of radiation on these films. The fact that the sol-gel method is easy to apply to different surfaces, allows working at low temperatures, is a cost-effective method, and is suitable for industrial applications as well as laboratory applications were effective in choosing this method. The dip coating method was chosen as a coating technique because it is a simple method, does not create waste material and allows for a homogeneous coating. As a result, it has been determined that the solutions synthesized by the sol-gel method can be produced homogeneously without any precipitation, the thin films prepared with these solutions show hydrophilic properties and have high surface roughness values which is dependent to film thickness. Through structural analysis, it was determined that the films produced were polycrystalline and face-centered cubic in structure and consisted of two phases (NiO and Ni2O3). Additionally, it was determined that the band gaps of the films varied between 3.66 - 3.90 eV. It has been observed that the optical transmittance value in the visible region of films produced with different thicknesses varies from 67% to 40%, and the annealing time and stabilizer type have a negligible effect on these properties. It was determined that the crystal structure properties of the irradiated films improved and their optical transmittance values decreased. Keywords: p-type semiconductor, nickel oxide (NiO), sol-gel dip coating, gamma radiation