Linearization and characterization of the Wemple – DiDomenico model of ZnO/Ni/ZnO tri-layer thin films prepared by ALD and DC magnetron sputtering

Abstract

Our present work is devoted to analyzing the influence of Ni on the optical properties of ZnO thin films deposited on glass and Si (100) substrates, with the use of ALD for ZnO deposition and DC magnetron sputtering for Ni interlayer deposition. The compositions as well as the crystalline structure of various multilayer thicknesses of Ni (10, 30, 50, and 70 nm), that sandwiched between ZnO Films (70 nm), before being optically characterized, were carried out by the X-ray diffraction (XRD). Based on the XRD results, the crystallite size was increased with the increase of the Ni interlayer concentration. Additionally, the material densities for both ZnO and Ni show the expected close-to-bulk values in all formations, where the large cavities between atoms, on the films make the dislocation density become smaller and the surface roughness values decrease as well, with the increase of Ni interlayer concentration. Different optical properties were observed for different Ni content. The optical absorption coefficient (α), refractive index (n), and extinction coefficient (k) have been deduced from the transmission T(λ) and absorption measurements A(λ). The optical energy gap Egoptare estimated from Tauc΄s extrapolation procedure and the Kubelka-Munk approach. The static refractive index (no), the oscillator energy (Eo), and the dispersion energy (Ed) are calculated using the Wemple-DiDomenico (WDD) theoretical model. Analysis of third-order nonlinear optical properties in crystalline ZnO/Ni/ZnO are being detailed. These promising results imply that the high-quality films produced by ALD, show how the insertion of Ni could enhance the quality of the optical properties of ZnO films.