Eutaxial growth of hematite Fe2O3 films on perovskite SrTiO3 polycrystalline substrates

a r t i c l e i n f o Keywords: Epitaxy Electron backscatter diffraction Fe 2 O 3 Pulsed laser deposition Eutaxy Combinatorial substrate epitaxy Perovskite SrTiO 3 The grain-by-grain orientation relationships between an Fe 2 O 3 film, grown using pulsed laser deposition, and a polycrystalline SrTiO 3 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 ori-entations in a single experiment, allowing the determination of the preferred epitaxial orientation (PEO) of this non-isostructural film/substrate pair. Heavily-twinned rhombohedral α-Fe 2 O 3 (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: 0001 ð Þ 1010 h i Fe2O3 111 ð Þ 110 h i SrTiO3. This OR aligns the eutactic (nearly close-packed) planes and directions between these dissimilar crystal structures. Importantly, the growth of Fe 2 O 3 on a single crystalline (100)-SrTiO 3 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. Epitaxy, or the ordered growth of one crystal on another [1–4], has played a central role in a range of technological and scientific advances over the past century [1,4–8]. Surprisingly, we have a relatively crude physical understanding of what the preferred epitaxial orientation (PEO) is between two dissimilar solids (heteroepitaxy). The overwhelming majority of prior investigations into heteroepitaxy use single crystal substrates exposing low Miller-index, high-symmetry surfaces to the growing solid. From the point of view of interface crystallography, this work is restricted to a very narrow region of epitaxial orientation space (herein defined relative to the substrate surface normal) and focuses on what should be considered extremely special interfaces. Most models of epitaxy aim to simplify the nucleation energetics to descriptors of the geometric match between the two crystals at these special interfaces [4,5,9–13,6,14–16]. A simple question arises: does ep-itaxial growth …