Spray pyrolysed bismuth oxide thin films and their characterization

Uniform, adherent and reproducible bismuth oxide thin films have been deposited on glass substrates from aqueous Bi(NO3)3 solution, using the solution spray technique. Their structural, surface morphological, optical, and electrical properties were investigated by XRD, AFM, optical absorption, electrical resistivity and thermo-emf measurements. The structural analysis from XRD pattern showed the formation of mixed phases of monoclinic Bi2O3 (predominant), tetragonal β-Bi2O3 and nonstiochiometric Bi2O2.33. The surface morphological studies on atomic force micrographs revealed round grain morphology of bismuth oxide crystallites. The optical studies showed a direct band gap of 2.90 eV for as-prepared bismuth oxide films. The electrical resistivity measurements of bismuth oxide films indicated a semiconducting behavior with the room temperature electrical resistivity of the order of 107 Ω cm. From thermo-emf measurements, the electrical conductivity was found to be of n-type.