Synthesis of (Bi2O3)1-x(PbO)x Thin Films by Plasma-Assisted Reactive Evaporation

Thin, dense and nanocrystal bismuth oxide films were prepared by the in situ plasma-assisted reactive evaporation (ARE) method using lead doping. Thin films were deposited at room temperature and at 500 °C temperature on glass and silicon substrates. X-ray diffraction, SEM, EDS, and optical measurements were applied to characterize these bismuth oxide films. The results showed that it is possible to synthesize the δ-Bi2O3 phase thin films at a temperature lower than 729 °C using an plasma-assisted reactive evaporation (ARE) method and stabilize it (to room temperature) using the additives of lead oxide. The influence of lead oxide concentration on phase formation was investigated. The optimal amount of lead oxide dopant was determined. An excess of lead oxide concentration forms PbO and δ-Bi2O3 mixture phases and nanorods appear in films. The synthesized δ-Bi2O3 phase was metastable; it transformed into the β-Bi2O3 phase after thermal impact during impedance measurements. The cross section of thin film sample shows the dense and monolithic structure. Optical measurements show that the optical band gap increases with increasing lead concentration. It was found that the highest total ionic conductivity of (Bi1−xPb0.26)2O3 is 0.165 S/cm at 1073 K temperature and activation energy is ΔEtot = 0.5 eV.