Eutaxial growth of hematite Fe2O3 films on perovskite SrTiO3 polycrystalline substrates

• Local orientations were determined for Fe2O3 films on polycrystalline SrTiO3.
• Hematite grew epitaxially over all orientation space of the perovskite substrate.
• > 90% of film grains had a single orientation relationship with the substrate.
• The preferred epitaxial orientation aligns the eutactic planes and directions.
• Eutaxial growth is revealed as a general phenomenon using high-throughput methods.

The grain-by-grain orientation relationships between an Fe2O3 film, grown using pulsed laser deposition, and a polycrystalline SrTiO3 substrate were determined using electron backscatter diffraction. This high-throughput investigation, we call combinatorial substrate epitaxy, enables the characterization of film growth on all grain orientations in a single experiment, allowing the determination of the preferred epitaxial orientation (PEO) of this non-isostructural film/substrate pair. Heavily-twinned rhombohedral α-Fe2O3 (hematite) grew epitaxially over the entire orientation space of the cubic perovskite substrate. Over 500 local orientation relationships (ORs) were investigated and more than 90% of these ORs, regardless of the interface plane normal, could be described using a single epitaxial OR  : 0001101¯0Fe2O311111¯0SrTiO3. This OR aligns the eutactic (nearly close-packed) planes and directions between these dissimilar crystal structures. Importantly, the growth of Fe2O3 on a single crystalline (100)-SrTiO3 results in several different orientation relationships. These results suggest that growth on high Miller-index (low-symmetry) surfaces provides more general information about the PEO than growth on low Miller-index (high-symmetry) surfaces. The epitaxial film growth on high Miller-index surfaces and the overwhelming observation of the eutaxial OR support the hypothesis that a very small number of simple crystallographic descriptors guide epitaxial film growth over all of orientation space, even for non-isostructural film/substrate pairs.