Bilayer number driven changes in polarizability and optical property in ZnO/TiO2 nanocomposite films prepared by ALD

Abstract Samples of ZnO/TiO2 bilayer films with various layer thickness were fabricated by atomic layer deposition (ALD). The X-ray diffraction (XRD) patterns revealed the absence of sharp peaks and confirms the amorphous nature of the samples under study. The absorption spectra of ZnO/TiO2 for the three samples were obtained in view of incident wavelength range (350 – 700 nm). The absorption spectra were used to determine the optical energy band gap. The experimental results show that the direct optical band gap (Eg) grown on glass substrate was obviously affected by the increase of the number of ZnO/TiO2 bilayers and found to decrease from (3.45 to 2.96 eV). The transition power factor (PF) for the three samples was applied to confirm the direct optical transition. A suitable relationship between the linear refractive index (n0) and the optical energy band gap (Eg) determined from the experimental and theoretical data was proposed for providing good basis for predication the metallization and polarizability criterion and other related parameters, such as optical dielectric constant and electrical susceptibility. The deep analysis of the studied properties, based on the variation of the number of the bilayer of ZnO/TiO2, makes the incorporation of these two materials promising candidates in various optoelectronic applications and solar cell devices.