| The high temperature phase of Bi2O3, delta-Bi 2O3, is an exceptional oxygen ion conductor, but only exists thermodynamically from 25°C to 825°C. In this work, this cubic phase has been stabilized to room temperature using thin film growth and epitaxy, both by using metal-organic chemical vapor deposition and by sputtering. The (001)-oriented delta-Bi2O3was grown on the single crystal perovskite substrates (001) SrTiO3 and (110) DyScO 3, and represents the first example of epitaxially strained (001)-oriented delta;-Bi 2O3. This material grew as islands when grown at substrate temperatures of 500°C and above, whereas continuous thin films of delta-Bi 2O3 were grown on (001) SrTiOsub>3 at a substrate temperature of 150°C by sputtering. This work is the first successful growth of the delta phase using the metal-organic precursor Bi(Ph)3 and the first example of sputtering in a pure oxygen environment using a Bi 2O3 target.;The samples that were grown were studied at the synchrotron (Advanced Photon Source) to understand their room temperature structure and stability. The structure of the islands was shown to follow Fm3m diffraction rules for the delta-Bi2O3 phase, but also had a set of extra peaks that represented a tripling of the unit cell. These islands were identified as (001)-oriented delta-Bi2O3, but the source of the superstructure is left for future work. In addition, the brightness of the synchrotron source allowed for in-situ characterization during annealing under a controlled oxygen atmosphere. The islands were stable up to 600°C, at which time the structure relaxed and a new epitaxial phase was nucleated. In contrast to the islands, the continuous thin film was (001)-oriented delta-Bi 2O3 with no superlattice peaks. The stability, however, was much reduced as compared to the islands, with a new Fm3m forbidden peak (221) appearing at 100°C. Attempts to measure the electrical properties of these continuous thin films indicated that the electrical properties are unstable. The room temperature dielectric constant was identified as ranging between 24 and 29, and the conductivities ranged in the 10-8 S/cm to 10-9 S/cm regime. |
