Abstract
We report the synthesis and characterization of pure ZnO, pure CeO2, and ZnO:CeO2 mixed oxide thin films dip-coated on glass substrates using a sol-gel technique. The structural properties of as-prepared thin film are investigated using the XRD technique. In particular, pure ZnO thin film is found to exhibit a hexagonal structure, while pure CeO2 thin film is found to exhibit a fluorite cubic structure. The diffraction patterns also show the formation of mixed oxide materials containing well-dispersed phases of semi-crystalline nature from both constituent oxides. Furthermore, optical properties of thin films are investigated by performing UV–Vis spectrophotometer measurements. In the visible region, transmittance of all investigated thin films attains values as high as 85%. Moreover, refractive index of pure ZnO film was found to exhibit values ranging between 1.57 and 1.85 while for CeO2 thin film, it exhibits values ranging between 1.73 and 2.25 as the wavelength of incident light decreases from 700 nm to 400 nm. Remarkably, refractive index of ZnO:CeO2 mixed oxide-thin films are tuned by controlling the concentration of CeO2 properly. Mixed oxide-thin films of controllable refractive indices constitute an important class of smart functional materials. We have also investigated the optoelectronic and dispersion properties of ZnO:CeO2 mixed oxide-thin films by employing well-established classical models. The melodramatic boost of optical and optoelectronic properties of ZnO:CeO2 mixed oxide thin films establish a strong ground to modify these properties in a skillful manner enabling their use as key potential candidates for the fabrication of scaled optoelectronic devices and thin film transistors.
Highlights
Zinc oxide (ZnO) is an essential and promising material for several modern technological applications owing to its high transmittance of visible light, wide direct band gap of 3.37 eV, Photonics 2020, 7, 112; doi:10.3390/photonics7040112 www.mdpi.com/journal/photonicsPhotonics 2020, 7, 112 extremely large exciting binding energy, high electrochemical stability, high semiconductor resistivity and non-toxicity [1,2,3,4]
X-Ray Diffraction (XRD) patterns confirm that ZnO thin film is polycrystalline and exhibits wurtzite hexagonal structure [3,43]
We calculate the density of dislocations (δ) by using the line profile analysis of XRD (LPA-XRD) patterns and using simple Williamson-Smallman formula given by δ = 1/D2, where D is the crystallite size calculated using Williamsons Hall equation [48,58,59,60,61]
Summary
Zinc oxide (ZnO) is an essential and promising material for several modern technological applications owing to its high transmittance of visible light, wide direct band gap of 3.37 eV, Photonics 2020, 7, 112; doi:10.3390/photonics7040112 www.mdpi.com/journal/photonics. ZnO:CeO2 mixed oxide thin films stems from their anticipated optical applications They have been widely used as key potential components for UV filters and high refractive index optical devices. They have been implemented increasingly nowadays to produce materials for human skin protection from the hazardous UV radiations Owing to their serious drawbacks such as fractional degradation and, high UV absorption, when exposed to UV light, organic UV blockers are not appropriate especially for people with medical records that indicate potential photo allergy [36]. Single-mode polymer waveguides suffer from serious drawback caused by Fresnel losses result from the mismatch in the refractive index values between the metal oxides and the semiconductor-based device. We report the crystallography, microstructure, crystal defects and optoelectronic properties of ZnO:CeO2 mixed oxides thin films fabricated by sol–gel method
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