Structural and optical characteristics of bismuth oxide thin films

The formation of different phases of Bi–O system during oxidizing process of Bi films from the viewpoint of structure characteristics and optical properties, is investigated. As revealed by structure and surface investigations, the thermal oxidation, in air, of Bi films on glass results in polycrystalline and multiphase bismuth oxide films. At substrate–film interface an amorphous oxide layer forms up, to whom surface the growth processes of crystallites belonging to divers phases, with different geometric shapes occur. For nanometric up to submicronic thicknesses, BiO is predominant phase, while in case of micronic films, α-Bi2O3 and Bi2O3 are the main phase components. From absorption curves the band gap values, (Eg=2.29–3.31 eV), for direct transitions, have been determined and an energy gap of ∼2 eV for amorphous phase was found.