The Effects of Thermal Annealing on ZnO Thin Films Produced by Spin-Coating Method on Quartz Substrates

Abstract

In this work, zinc oxide (ZnO) thin films on quartz substrates were fabricated using the spin-coating method. Thermal annealings from $$350\,^{\circ }\hbox {C}$$ to $$1050\,^{\circ }\hbox {C}$$ have been performed in $$50\,^{\circ }\hbox {C}$$ increments and for two annealing durations (0.5 h and 8 h). X-ray diffraction (XRD) spectra, scanning electron microscopy micrographs, and UV–Vis absorption spectra of all the samples have been elucidated from mechanical and optical points of view. It has been observed that for all annealing temperatures, the crystal phase has been obtained. After $$850\,^{\circ }\hbox {C}$$ annealings, a new crystal phase related to $$\hbox {Zn}_{2}\hbox {SiO}_{4}$$ (willemite) has also been appeared in XRD spectra. This phase remained stable up to $$1050\,^{\circ }\hbox {C}$$ annealing together with the ZnO crystal phase. It has been found that the nano/micro rod diameters of the ZnO crystals reach to a maximum $$(0.4\,\upmu \hbox {m})$$ at the $$700\,^{\circ }\hbox {C}$$ annealing for both annealing durations. For $$650\,^{\circ }\hbox {C}$$ annealings, ZnO nanorods appeared to be split into two homogeneous nanorods of length of $$500\,\upmu \hbox {m}$$ and of width of $$0.35\,\upmu \hbox {m}$$ (350 nm) which was not the case for all other annealing temperatures. After $$950\,^{\circ }\hbox {C}$$ annealings, ZnO nano/micro rods started to disappear and formed homogeneous ZnO thin films.