Influence of Substrate, Process Conditions, and Post-Annealing Temperature on the Properties of ZnO Thin Films Grown by SILAR Method

Abstract

Here we report the effect of substrate, sonication process, and post-annealing on the structural, morphological, and optical properties of ZnO thin films grown in presence of isopropyl alcohol (IPA) at temperature 30 – 65 ℃ by SILAR method on both soda lime glass (SLG) and Cu foil. The X-ray diffraction (XRD) patterns confirmed the preferential growth of ZnO thin films along (002) and (101) plane while grown on SLG and Cu foil substrate respectively. Both XRD and Raman spectra confirmed the ZnO and Cu-oxide phases of the deposited films. Scanning electron microscope (SEM) image of the deposited films shows compact and uniformly distributed grains for samples grown without sonication while using IPA at temperature 50 and 65 ℃. The post-annealing treatment improves the crystallinity of the films, further evident by XRD and UV-VIS-NIR results. The estimated optical bandgaps are in the range of 3.37-3.48 eV for as-made samples. Results revealed that high-quality ZnO thin films could be grown without sonication using IPA dispersant at 50 ℃, which is much lower than the reported results using the SILAR method. This study suggests that in the presence of IPA, the SLG substrate results in better c-axis oriented ZnO thin films than that of DI water, ethylene glycol, propylene glycol at the optimum temperature of 50 ℃. Air-annealing of the samples grown on Cu foils induced the formation of CuxO/ZnO junctions which is evident from the characteristic I-V curve including the structural and optical data.