Composition, morphology and particle size control in nanocrystalline iron oxide films grown by single-source CVD

摘要

Nanocrystalline iron oxide films have been deposited onto various substrates in a cold-wall CVD reactor using iron (Ⅲ) tert-butoxide as a single-source for iron and oxygen. Influence of the CVD parameters on the growth rate, chemical composition, morphology and crystalline phases has been investigated. The Fe:O stoichiometry in the films is sensitive to the deposition conditions. For instance, the interplay between precursor flux/deposition temperature allows a fine control over deposition of different iron oxide phases (hematite, maghemite and magnetite) and their interconversion. The different iron oxides could be detected by their typical morphological features and confirmed by XRD and XPS data of the deposits. At 350℃ and below, ultrafme amorphous iron oxide grains with size lower than 10 nm are produced which, can be transformed to crystalline hematite or magnetite phases by ex-situ annealing. Spinel-type Fe_3O_4 was formed as a singular phase on copper at 450℃, which could be converted to Fe_2O_3 upon annealing. On silicon, a mixture of magnetite and hematite was formed at 450℃ while a solid solution of the two phases resulted at 500℃. Transmission spectra of films deposited on glass show them to be transparent to visible light. The results are discussed in the light of XRD, SEM-EDX, XPS, AFM and elemental analysis.