The effect of solution pH on the structural, surface morphological, and optical characteristics of ZnO thin films synthesized by the chemical bath deposition technique

Abstract

The presented work utilizes the chemical bath deposition technique to fabricate zinc oxide nano-thin films on a glass substrate. The quality of synthesized films is dependent on the deposition parameters, which include the solvents and metal salts used, as well as the bathing time and temperature. The impact of the pH value of the solution on the crystal structure, surface morphological, and optical characteristics of zinc oxide thin films was studied in this respect. An XRD diffractometer was used to determine the structural characteristics; a scanning electron microscope was utilized to analyze the surface topology. The linear optical properties were carried out using a UV–VIS spectrometer. The XRD results showed an increase in grain size from 36.06 nm to 42.23 nm as the pH value increased from 8 to 10. The Debye-Scherrer method was utilized to assess crystal grain size and microstrain along (1 0 1) orientation. SEM images showed a significant correlation between grain size distribution and precursor’s solution pH. All the deposited films have shown more than 86% optical transparency, suggesting that these obtained films are best suitable for transparent conducting electrodes for display devices. However, the optical transparency of the deposited films has decreased with an increase in pH value, which may be attributed to increased film thickness. The sample deposited at pH: 10 exhibited the minimal optical bandgap of all the samples.