Abstract
MgxZn1−xO thin films were deposited on glass substrate with x varied between 0.01 and 0.05 by spray pyrolysis at a temperature of 450 °C. The structural investigation showed that all thin films had ZnO wurtzite structure with a preferred (002) orientation. The gap energy was calculated using Tauc’s plot, and it decreased over the Mg content by 0.07 eV. The charge carriers’ density dropped by an order of 105 as Mg content increased whereas the resistivity and the mobility increased. SEM observations revealed a significant difference between undoped and doped thin films. A 632.8 nm laser source prism coupler revealed 2 optical modes for every thin film in each Transverse Electric and Transverse Magnetic mode, and the birefringence of the Mg-doped films was positive. Both ordinary and extraordinary refractive indices were found to decrease as the Mg content increased. Great intention has been paid to the relation between the refractive, charge carriers’ density, and the optical band gap.
Highlights
Zinc Oxide (ZnO) is is a multipurpose semiconductor with many uses such as ultra-capacitor electrode [1], spintronic devices [2], multigas and vapors sensing [3,4,5,6,7], piezoelectric devices [8], ultra-violet LEDs [9], UV detector [10, 11], transistor [12] as well as waveguides [13,14,15]
The grain size can be calculated by DebyeScherrer formula [35]: where λ is the wavelength of the incident X-ray, θ is the Bragg’s angle, K is the shape factor (0.9 for gaussian fit) and β is the Full Width at Half Maxima (FWHM) of the peaks
Sorar et al [64] found that the ordinary refractive index generally decreases with the increase of the Si doping in ZnO thin films prepared by sol-gel and annealed at 350 °C and 550 °C whereas their optical band gap energy was found to be blue shifted
Summary
Zinc Oxide (ZnO) is is a multipurpose semiconductor with many uses such as ultra-capacitor electrode [1], spintronic devices [2], multigas and vapors sensing [3,4,5,6,7], piezoelectric devices [8], ultra-violet LEDs [9], UV detector [10, 11], transistor [12] as well as waveguides [13,14,15]. Wurtzite MgxZn1−xO alloy is very interesting due to the high solubility of Mg in the ZnO wurtzite matrix (up to 30%) [28] It offers control over a range of optical and electrical properties of ZnO such as widening of the optical gap energy up to 0.85 eV [29], it can be used for multiple purposes such as a top layer in MgxZn1−xO/ZnO multilayer UV photodetector [30] and high mobility MgZnO/ZnO thin film transistor [31] to name few. We engaged in the investigation of the relations between the refractive index, the optical gap energy and the charge carriers’ density in addition to the birefringence of MgxZn1−xO thin films deposited by spray pyrolysis on glass substrate
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