Structural and optical changes induced by the incorporation of Fe ions in ZnO matrix
摘要
In this work, Fe ions were incorporated in the ZnO matrix using a chemical method. This method consisted of the spray of a chemical solution onto glass substrates heated at 450 °C. The chemical solution was composed of a volume of Zn-rich solution in which Fe-rich solution was added with a volume ratio varied from x = 0.00 to x = 0.10. The resulting films were characterized for their structural and optical properties by, respectively, x-ray diffraction (XRD), Raman spectroscopy, UV–visible spectroscopy, and photoluminescence spectroscopy. XRD patterns showed that the incorporation of Fe ions in the ZnO matrix did not induce changes in the material’s wurtzite phase; however, it affected the structural parameters such as lattice parameters, grain size, and crystal stress. Raman spectra confirmed the presence of the ZnO phase in addition to two peaks at 646 and 690 cm−1 corresponding to the Fe–O vibration modes. The correlation between the E2H mode-related peak area and the grain size exhibited that the enhancement of the structural properties of ZnO depended on the incorporated Fe ions form and amount. The transmittance in the visible region decreased as a function of the Fe-rich solution volume ratio. The incorporation of Fe ions decreased the band gap energy Eg from 3.45 eV for x = 0.00 to a minimum of 3.21 eV for x = 0.04. Beyond this ratio, the band gap energy stabilized around 3.27 eV. PL spectra showed the presence of ultraviolet (UV) emission and near-infrared (NIR) emission peaks. The variation of the band gap energy corresponding to the position of the UV emission peak is similar to that determined from UV–visible spectra. The decrease of the NIR emission peak intensity is attributed to the presence of Fe ions in the ZnO matrix. The optical properties of ZnO depended, like structural properties, on the incorporated Fe ion form and amount.