Oxide thin-films: Epitaxy, reactions and interfaces

Thin-film diffusion couples have been used to study epitaxy, solid-state reactions and interfaces in the spinel-forming systems: Fe2O 3/MgO, Fe2O3/NiO and In2O3/MgO. In the system Fe2O3/MgO, the growth of an Fe-oxide thin film on a (001)-oriented MgO substrate was investigated. It was found that for shorter deposition times, thinner film thicknesses, the spinel phase of Fe-oxide occurred, while for longer deposition times, thicker film thicknesses, the corundum phase of Fe-oxide formed.;The corundum-structured alpha-Fe2O3 thin film on MgO substrate was subsequently used to characterize MgFe2O 4 spinel-forming reaction kinetics. This system exhibits diffusion control kinetics for reaction layers as thin as 50 nm.;In the system, Fe2O3/NiO, three methods for producing NiFe2O4 thin-films were utilized by depositing on alpha-Al 2O3 substrates. In the first method, a NiFe2O 4 film was deposited directly onto alpha-Al2O3. While in the latter two methods the spinel-forming reaction between NiO and Fe2O3 was used. In one case the growth temperature was high enough that the reaction occurred during deposition, while in another case the epilayers were deposited at lower temperatures and subsequently annealed ex-situ.;Finally, an electric field has been used to influence solid-state reactions and transport processes in two spinel-forming systems: Fe2O 3/MgO and In2O3/MgO. In the Fe2O 3/MgO system, a flux balancing of the cations in each layer of the diffusion couple was performed to describe the effect of an electric field on a spinel-forming reaction. Additionally, MgFe2O4 thin-films on a MgO single crystal substrate were used to investigate kinetic decomposition of spinel.;In2O3/MgO diffusion couples were also used to investigate the effect of an electric field on a solid-state reaction process. It was found that the applied electric field causes a morphological instability in the MgO/spinel interface. Additionally, Pt markers have been used as a fixed reference point in In2O3/MgO diffusion couples. Diffusion couples with markers were reacted both with and without an electric field to aid in determining the transport processes. However, it cannot always be assumed that such markers are inert. At times it was discovered that the markers affected or were affected by the reaction process occurring around them.