Non-linear Optical Properties of Nickel Oxide Undoped and (Li, Ca) Doped

Nickel oxide (NiO) has gained significant attention as a transparent conductive oxide material with promising physical properties for diverse technological applications. This thesis presents a comprehensive exploration of the structural and optical properties of undoped and doped nickel oxide (NiO) thin films, focusing on two key studies. The first study investigates the effects of Lithium doping on the structural and optical characteristics of NiO thin films. These films were deposited using spray pyrolysis on glass substrates at 480?ʻC, with varying concentrations of Li doping. Structural analysis through X-Ray Diffraction (XRD) revealed a polycrystalline cubic structure, predominantly oriented along the (200) crystal plane. The films exhibited a remarkable transmittance ranging between 60% and 80%. The bandgap values (Eg) were significantly influenced by the Li doping ratios, varying from 3.38 to 3.66?eV. Furthermore, a thorough examination of linear and nonlinear optical properties indicated improvements in ?1, ?3, and n2 with the incorporation of lithium doping into the NiO lattice. The second study focuses on producing and characterizing undoped and calcium-doped NiO thin films using the Spray Pyrolysis Technique. The XRD investigation indicates that the produced films have a cubic structure and grow preferentially along (111) planes. The introduction of calcium reduced the crystallite size from 31 to 14 nm. SEM images identified agglomerations of particles with micropores, while elemental compositions were confirmed through EDX spectrum analysis. Transmission and reflection measurements in the 200-900 nm wavelength range were used to determine the optical constants. The direct energy gap values ranged from 3.30 to 3.43?eV. Nonlinear susceptibility (?3) and refractive index nonlinearity (n2) were also studied, revealing their sensitivity to calcium doping content.