A Study on the role of solvent on properties of GdxZn1−xO films synthesized by sol-gel method

The increasing demand for high-performance and low cost optoelectronic devices motivates many researchers to develop more efficient transparent conductive oxide (TCO) films. Among the popular TCOs, the past decade has seen the emergence of zinc oxide (ZnO) as one of the potential materials for the fabrication of transparent conductive electrodes. The aim of this work is to study the influence of different solvents on the properties of GdxZn1-xO (x ≤ 0.01) films synthesized by sol-gel spin coating technique. Consequently, three different solutions were prepared with different solvents [2-Methoxyethanol (2-ME), ethanol (EtOH) and isopropanol (IPA)]. The structural, surface roughness and optical properties were investigated using an X-ray diffractometer (XRD, PANanalytical xpert-pro), atomic force microscope (AFM, Park XE-100) and ultra violet-visible spectrophotometer (UV-Vis, Shimadzu UV 1800), respectively. As a result, all films were found to have polycrystalline with hexagonal wurtzite structure. In addition, AFM analysis revealed that the film synthesized using EtOH exhibiting the smallest surface roughness of about 4.12 nm compared with IPA and 2-ME of about 5.12 nm and 12.22 nm, respectively. Also, the optical transmittance spectra indicate that all films exhibit good transparency in the visible spectral range with an average transmission of approximately 97.5%, 97.2% and 96.1% for EtOH, IPA and 2-ME, respectively. The optical band gap energy (Eg) values was estimated to be around 3.26 ~ 3.30 eV using Tauc's model with the lowest value for IPA (3.26 eV) and highest for 2-ME (3.30 eV). In a nutshell, the solvents are playing a key role for controlling the growth and nucleation in the preparation of GdxZn1-xO solution and it strongly affects the properties of the film.