Fabrication and characterization of ZnO/TiO2 multilayers, deposited via spin coating method

Zinc oxide (ZnO) and Titanium dioxide (TiO2) nano-particles were synthesized by sol–gel method. Next, (ZnO/TiO2) mono, double and multilayers were deposited by spin-coating technique on glass substrates. Structure, chemical bonds, optical properties, nano-particles size, surface morphology and multilayers structure were studied using X-ray diffraction (XRD) technique, Fourier Transform Infrared and UV-Vis-NIR spectroscopy, Transmission Electron Microscopy and Field Emission Scanning Electron Microscopy (FESEM), respectively. XRD results described the Wurtzite crystalline phase for ZnO and Anatase phase for TiO2 layers. Moreover based on Scherer equation, the TiO2 and ZnO nano-crystallites sizes were estimated about 11 and 25 nm respectively. XRD results also described increase of the layers crystallinity with increase of the layers number. Optical studies described despite of band-gap widening, transparency decreased with increase of layers number. This effect was attributed to the thin films thickness. TEM images described that the TiO2 nano-particles were smaller than ZnO one while more coalesced. FESEM images revealed that the multilayers contained of a flat and homogenous surface.