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Title: Growth of bismuth oxide and bismuth ferrite thin films via CVD
Author: Moniz, S. J. A.
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2012
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This thesis describes the growth of bismuth oxide (Bi2O3) and multiferroic bismuth ferrite (BiFeO3) films via chemical vapour deposition (CVD). The synthesis of a range of bismuth(III) β-diketonate complexes was carried out via a ligand-exchange reaction between [Bi(N(SiMe3)2)3] and the respective free ligand, and crystal structures of [Bi(dbm)3]2 and [Bi(acac)3] are reported. The decomposition of these complexes was studied via DSC-TGA to assess their potential as single-source precursors to Bi2O3, and the mass transport characteristics of the volatile complexes [Bi(mmp)3], [Bi(thd)3] and [Bi(OtBu)3] were studied. Bi2O3 films were grown via the LPCVD reaction of the single-source precursor [Bi(OtBu)3]; the crystalline phase (and band-gap) of the resultant films depended strongly upon the reactor conditions. Films were tested for photo-oxidation of water under UV-light, revealing high activities comparable to those of TiO2 films described previously. [Bi(dbm)3]2 was utilised as a single-source precursor to β-Bi2O3 films via AACVD, together with the growth of Pt(0) films using H2PtCl6.6H2O as a precursor. Pt-nanoparticle Bi2O3 films were grown via a ‘one-pot’ AACVD reaction of both precursors; composite Pt-Bi2O3 films were able to evolve hydrogen via the photo-reduction of water, a property not observed for films containing either Pt or Bi2O3 alone. BiFeO3 films were grown via a multi-source LPCVD reaction between [Fe(acac)3], [Bi(OtBu)3] and air, as well as via the dual-source reaction of [Bi(OtBu)3] and [Fe(OtBu)3]2 without oxidising gas, and, furthermore, via the single-source precursor [{Cp(CO)2Fe}BiCl2] using AACVD. Magnetometry revealed low temperature ferromagnetism and spin-glass behaviour, characteristic of larger particle sizes. Ferroelectric measurements revealed low polarisation but nevertheless indicated films were multiferroic at room temperature. A selection of these films were tested for photo-oxidation of water under visible-light; films displayed high photoactivities with rates in excess of those from optimised TiO2 films measured under UV-light, highlighting the potential of BiFeO3 films as strong visible-light active photocatalysts.
Supervisor: Blackman, C. S. ; Carmalt, C. J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available