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Stabilization of Epitaxial α-Fe2O3 Thin Films Grown by Pulsed Laser Deposition on Oxide Substrates C

Serrano, Aida, Rubio-Zuazo, Juan, López-Sánchez, Jesús, Arnay, Iciar, Salas-Colera, Eduardo, Castro, Germán R.
Journal of physical chemistry 2018 v.122 no.28 pp. 16042-16047
aluminum oxide, hematite, physical chemistry
We have grown epitaxial incommensurate α-Fe₂O₃ thin films on α-Al₂O₃(0001), SrTiO₃(111), and LaAlO₃(001) substrates, identifying hematite as single iron oxide phase stabilized. We demonstrate that a different lattice coupling behavior as a function of the selected oxide substrate mediates the epitaxial character. Single-oriented α-Fe₂O₃(0001) layers are obtained on α-Al₂O₃(0001) and SrTiO₃(111) substrates, whereas on the LaAlO₃(001) substrate, the hematite layer is found to grow along the r-plane to adapt its hexagonal lattice on the cubic lattice of the substrate, evidencing a single-oriented (11̅02) layer. In the film plane, crystallographic axes of α-Fe₂O₃(0001) are collinear with the α-Al₂O₃(0001) ones, while a rotation of 30° is found between those of α-Fe₂O₃(0001) and SrTiO₃(111). On LaAlO₃(001), α-Fe₂O₃(11̅02) adopts an in-plane orthorhombic structure rotated 45° respect to the substrate lattice. The crystallographic domain size and the crystalline order are dependent on the incommensurate lattice coupling mechanism. Larger values are obtained for layers grown on α-Al₂O₃(0001), while lower values correspond to the hematite deposited on LaAlO₃(001). Moreover, an Fe–O elongation and Fe–Fe contraction of first neighbors distances as well as a dependency on surface flatness as a function of the substrate lattice parameter is also found.