Epitaxial Phase Stability of SrMnO_3–x Films on Polycrystalline Perovskite Substrates

Abstract

Combinatorial substrate epitaxy (CSE) was used to investigate the epitaxial phase competition between the threelayered cubic (3C) and the four-layered hexagonal (4H) perovskite polymorphs of SrMnO 3 . Films were deposited on polycrystalline 3C-SrTiO 3 and 4H-SrMnO 3 substrates as a function of substrate orientation, temperature, and oxygen pressure. Electron backscatter diffraction data was analyzed using a dictionary-based indexing technique to determine that the eutactic orientation relationship (OR) was the preferred epitaxial orientation for both polymorphs across all conditions and substrates. An increase in substrate temperature and a decrease in oxygen pressure were found to expand the range of substrate orientations that support 3C growth from ( 100) to ( 110) and, finally, to (111) when 3C appeared as the stable phase on all SrTiO 3 substrate orientations. In these conditions, the metastable 4H phase was then epitaxially stabilized on nonbasal orientations of 4H-SrMnO 3 . These results highlight how CSE can be used to understand phase competition and prepare novel metastable epitaxial films.

Epitaxial Stabilization and Persistent Nucleation of the 3C Polymorph of Ba0.6Sr0.4MnO3

“…4H Ba 0.6 Sr 0.4 MnO 3 targets were fabricated using conventional ceramic synthesis methods (described in Supporting Information S2.1). , 1 mm-thick single crystals (MTI Corporation) of orthorhombic (o) DyScO 3 (DSO) having (101) o orientations (which is equivalent to a pseudocubic (pc) (001) pc ) were used as substrates for most depositions. The lattice parameters for o-DSO are a = 5.720 Å, b = 7.903 Å, and c = 5.442 Å.…”

“…This poses difficulties when the thickness is such that the substrate contributes to the pattern or if more than one phase or orientation exists within the probed volume of the film, as indexation of multiple phases is significantly more difficult and is not routinely possible now. EBSD characterization details, examples of EBSD patterns from epitaxial films, and descriptions of orientation relationships (ORs) are given in prior work. ,,− …”