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A study of 8 MeV e-beam on localized defect states in ZnO nanostructures and its role on Photoluminescence and third harmonic generation
摘要： In this article we have explored an effect of electron beam irradiation (EBI) on physical and nonlinear optical properties ZnO thin nano films. Nanostructured ZnO thin films were grown by low cost spray pyrolysis technique. The irradiation dosage has been fixed at 5kGy, 10kGY, 15kGy and 20kGy. The structural investigation by Glancing angle X-Ray Diffractometer (GAXRD) confirms a polycrystalline phase of ZnO with wurtzite structure. The variation in the surface morphology upon EBI has been demonstrated using 2D and 3D Atomic force microscopy (AFM) images. Nanoscope software analysis quantifies the variation in surface roughness and average particle height upon EBI. The defect states created in the films upon irradiation experiments were investigated using UV- visible spectrophotometer, Room temperature Photoluminescence (RTPL), Raman and X-ray photoelectron spectroscopy (XPS). The increase in urbach tail validates the creation of localized defect states in the films The Gaussian fitting on RTPL spectra shows the quenching in the luminescent centers upon irradiation arised as result of recombination of vacancy defects. Phonon confinement model fitting on Raman spectra endorses that shift in the phonon modes observed on irradiation is due to spatial confinement of phonons. The elemental composition and impurity states of the EBI ZnO thin films were studied using XPS spectra. The shift in the binding energy of Zn and O elements infers the electron beam induced changes in the films. The electron beam irradiation has resulted in the increment of third order optical susceptibility χ(3) from 3.5×10-4esu to 8.13×10-3esu due to the enhancement of electronic transition to different defect levels formed in the films and through local heating effects arising due to continuous wave (CW) laser illumination. The enhanced THG signal investigated using Nd:YAG laser at 1064nm and 8 ns pulse width shows the promising features of EBI ZnO films for frequency tripling applications.
关键词： Electron beam irradiation,Phonon confinement model,third harmonic generation,ZnO nanostructures,Localized defect states
更新于2025-09-10 09:29:36
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Photocatalytic response of Fe, Co, Ni doped ZnO based diluted magnetic semiconductors for spintronics applications
摘要： Novel attempts were made to prepare diluted magnetic semiconductors separately with 10 at.% each of Fe, Co and Ni doped ZnO by sol-gel method. The XRD analysis of the films detect wurtzite ZnO as the pure phase present in the synthesized films. The average particle size of 10 at.% Fe, Co, Ni doped and pristine ZnO derived films are found as 10.01 nm, 12.03 nm, 15.36 nm and 16.16 nm respectively. The absorbance spectra of the oxides reveal intrinsic band gap of ZnO, Fe2O3, CoO and NiO are 3.29 eV, 2.53 eV, 2.42 eV and 3.64 eV respectively. The near band edge absorbance of pure ZnO was recorded as about 377 nm (～3.29 eV) which shifts to lower wavelength with reduction in particle size in Ni, Co and Fe doped ZnO sample as the effect of quantum confinement. The PL spectra of the developed films reveal multiple peaks between 450 nm and 500 nm, on excitation wavelength at 370 nm, as the evidence of photochemical properties of the samples. Vibrating sample magnetometer analysis reveals 10 at.% Fe doped ZnO posses minimum value of squareness 0.118 and coersivity 177.738 Oe which prove it to be the best magnetic material among all four samples prepared. Raman spectra show evidence of phonon confinement for 10 at.% Fe doped ZnO sample by broadening of Eg, T2g and A1g peaks, which is not so prominent for other samples. In addition, the photochemical degradation reaction is maximum for 10 at.% Fe doped ZnO sample which proves to be most suitable material for optoelectronic devices.
关键词： Solar spin,Zinc oxide,Photocatalytic response,Diluted magnetic semiconductors,Phonon confinement
更新于2025-09-10 09:29:36