iron doping effects on bizo3 optical filters

Abstract

In this thesis, we have discussed the effects of iron doping on the structural, morphological, compositional, optical and dielectric properties of bismuth oxide thin films. Bismuth oxide thin films of thicknesses of 0.50 µm were deposited by the thermal evaporation of Bi2O3 powders onto glass substrates under a vacuum pressure of ~ 10−4 mbar. Iron doping into the films was actualized by mixing the iron nanopowders with those of Bi2O3 before evaporation. Three increasable doping contents were used for this purpose. It was observed that the grown films are polycrystalline in nature. The doping strongly affected the crystallinity, as evidenced from the decreased crystallite sizes and increased micro-strains and defect densities upon doping. However, increasing the doping content showed less effect on the structural parameters even after the solubility limit of iron was exceeded (FBO − 13). The behavior is ascribed to the formation of iron oxide in the structure of bismuth oxide. The scanning electron microscopy showed grains with increasing sizes and different shapes based on the doping amount. Optically, the films showed low transmittance values and exhibited a red shift in the energy band gap with increasing doping content. On the other hand, the dielectric dispersion analyses have shown a well improved dielectric response suiting high k-gate dielectrics that are used in thin film transistor technology. The Drude-Lorentz model analysis that connects electrical parameters to those corresponding optical ones was fitted with the experimental data showing decreasing carrier density with increasing doping content. The doping showed no effect on the drift mobility or other related conduction parameters other than the Plasmon frequency, which decreased with increasing doping content. The work is promising as it enhances the performance of Bi2O3 and makes it adequate for electronic applications in isolation purposes.