nanolayers Thin films S1(b). interested like to note 3 film. Grazing

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1 Supplementary Material to Reconstruction of the polar interface between hexagonal LuFeO 3 and intergrown Fe 3 O 4 nanolayers A.R. Akbashev, V.V. Roddatis, A.L. Vasiliev, S. Lopatin, V.A. Amelichev, and A.R. Kaul Thin films of hexagonal LuFeO 3 were grown on single crystalline (111) ZrO 2 (Y 2 O 3 ) substrates at 9000 C using MOCVD with a flash evaporation at 250 C of a mixture of Lu(thd) 3 and Fe(thd) 3 (thd=2,2, 6,6 tetramethylheptane 3,,5 dionate) precursors. The total pressure was 5 mbar, the oxygen partial pressure was 1 2 mbar. X ray diffraction study of thin films was performed using Rigaku SmartLab 5 circle X ray diffractometer. Fig. S1(a) shows the 2θ/ω XRD pattern of the LuFeO 3 film. Grazing incidence XRD in the 2θχ/ϕ geometry of the (110) and (300) reflectionss of LuFeO 3 are shown in Fig. S1(b). FIG. S1. XRD patterns of the LuFeO 3 thin film deposited onn ZrO 2 (Y 2 O 3 ): (a) 2θ/ω geometry and (b) grazing incidence 2θχ/ϕ scan. Since in our experiments metal organic species Lu(thd) 3 and Fe(thd) 3 are used, one may be interested if the the reducing gas phase species that appear during CVD process could shift the stability region of Fe 3 O 4. We would like to note that the growth rate of the films was rather small (5

2 nm/min) and the precursor feeding portion was as small as mg/min. In our MOCVD processes, after the feeding of the precursors into the reactor is stopped and the deposition is finished, the films are annealed and cooled down inside the reactor in the same Ar/O 2 flow. According to a considerable experience of the authors of the manuscript (see, for example, Ref. [1 10]), this annealing does undoubtedly lead to the equilibrium between the thin film material and the gaseous phase. In principle, the local value of p(o 2 ) in the zone, where the oxidation of metal organic precursors takes place, may be different from the average value despite a very large excess of oxygen (relative to the amount of oxidized organic ligands). Such a change of p(o 2 ) induced by CO/CO 2 and H 2 O can indeed be observed, but only in the direct liquid injection MOCVD process, where precursors are first dissolved in organic solvent, and then this low concentration solution is fed into the reactor. In this case a large quantity of the organic solvent is constantly injected into the substrate area during deposition and is able to change p(o 2 ). In our current report we intentionally did not use the direct liquid injection MOCVD process, but instead used the procedure, in which the powder mixture of precursors is fed into the reactor by small portions (~20 microgram per second). When metal organic precursors are oxidized, the CO/CO 2 and H 2 O gases appear. When the deposition is finished, even a short time annealing in the flow of Ar/O2 ensures that the film reaches equilibrium with the surrounding atmosphere. HAADF STEM images were obtained using probe corrected FEI Titan S/TEM operating at 300 kv. Fig. S2 shows the growth of the LuFeO 3 thin film on the substrate (Fig. S2(b)) up to the first magnetite nanolayer (Fig. S2(a)). In Fig. S3(a) a low resolution HAADF STEM image shows that continuous nanolayers of Fe 3 O 4 extend along and beyond the entire image that shows 1.2 micrometer of the film. We did not find any dislocations along the interface between magnetite and hexagonal LuFeO 3. In Fig. S3 (d) and (e) images of atomically resolved EDS mapping of Lu and Fe are shown. A combination of HAADF STEM image with Fe and Lu maps is shown in Fig. S3(f), where structural reconstruction can be clearly identified both at the lower and upper interfaces.

3 Fig. S2. HAADF STEM images of (a) the first Fe 3 O 4 nanolayer with a non reoriented (001) LuFeO 3 sublayer below and (b) the growth of this (001) LuFeO 3 sublayer on the (111) ZrO 2 (Y 2 2O 3 ) substrate. The distances between atomic columns in Fig. 2(e) were calculated from the corresponding plotted EDS profiles that contain at least 6 peaks for each distance. The average value was then calculated and presented in Fig. 3(e).

4 FIG. S3. (a b) Low resolution HAADF STEM images of LuFeO 3 thin film with continuous intergrownn magnetite nanolayers. (c e) atomically resolved HAADF STEM image and EDS mapping of Lu and Fe in the magnetite with the neighboring LuFeO 3 phase. (f) Combined HAAD STEM, Fe map and Lu map image. The scale bar in (c f)) is 1 nm. Fig. S4 shows the difference between centrosymmetric (YAlO 3 type) and non centrosymmetric (YMnO 3 type) structures of LuFeO 3. The non centrosymmetric of the Lu atoms alongg the c axis when the crystal undergoes a structure can exhibit ferroelectric ordering: yellow arrows are the shifts transition into a ferroelectric phase. For each Lu 3+ ion shifted in the 001 direction there are 2 Lu 3+ ions per unit cell shifted along the [001] direction. In the centrosymmetric crystal structure there are no shifts of Lu or Fe atoms. In the LuFeO 3 thin film we also observed the change of the structure orientation represented by differently shifted Lu 3+ ions (up up down or down down in up along the [001] axis), which is a reminiscence of oppositely oriented ferroelectric domains hexagonal RMnO 3.

5 FIG. S4. Ferroelectric (space group P6 3 cm) and paraelectric (space group P6 3 /mmc) phases of hexagonal RMO 3 (M=Fe, Mn). Colored arrowss indicate the unit vectors. FIG. S5. Atomic structure of the coherent interface betweenn (111) Fe 3 O 4 and (001) LuFeO 3, favoring epitaxial growth. Colored arrows indicate the unit vectors. In Fig. S5 the scheme illustrating the epitaxy of magnetite onn hexagonal LuFeO 3 is shown. 2 is the length of the face diagonal line of the Fe 3 O4 cubic unit cell and it is equal to the doubled a lattice parameter of hexagonal LuFeO 3. From our study it is not clear if the initially observed in planee reorientation of hexagonal RFeO 3 due to the formation of the Fe 3 O 4 inter grown nanolayers is the onlyy reason for the (110) peak appearance in the XRD patterns. All schemes of structures were made using VESTA software [11]. References 1. O.Yu. Gorbenko, A.A Bosak. Growth of LaNiO3 thin films onn MgO by flash MOCVD. Journal of Crystal Growth 186 (1998), A.A. Bosak et al. Epitaxial phase stabilisation phenomena in rare earth manganites.. Thin Solid Films 400 (2001), I. E. Graboy et al. HREM Study of Epitaxially Stabilized Hexagonal Rare Earth Manganites. Chem. Mater. 15 (2003), A.A. Bossak et al. XRD and HREM Studies of Epitaxially Stabilized Hexagonal Orthoferrites RFeO 3 (R= Eu Lu). Chem. Mater. 16 (2004), A.Kaul, O.Gorbenko, I.Graboy, M.Novojilov, A.Bosak, A.Kamenev, S.Antonov, I.Nikulin, A.Mikhaylov, M. Kartavtzeva. Epitaxial Stabilization in Thin Films of Oxides. Mat. Res. Soc. Symp. Proc. Vol. 755 (2003), DD DD

6 6. A.R. Kaul, O.Yu. Gorbenko, I.E. Graboy, S.V. Samoilenkov, M.A. Novojilov, A.A. Bosak, H.W. Zandbergen, G. Wahl. Epitaxial phase stabilization in thin films of complex oxides. International Journal of Inorganic Materials 3 (2001), Samoylenkov S.V. et al. Metalorganic chemical vapour deposition of high quality LuBa 2 Cu 3 O 7 δ thin films: Peculiarities of growth and superconducting properties. Journal of Alloys and Compounds 251 (1997), A.A. Bosak, S.V. Samoilenkov, O.Yu. Gorbenko, A.N. Botev, A.R. Kaul. Self tuning MOCVD approach to the growth of very smooth La 1 x Pb x MnO thin films. International Journal of Inorganic Materials 3 (2001), O.Yu. Gorbenko et al. Synthetic routes to colossal magnetoresistance manganites thin films containing unstable or highly volatile metal oxides. Thin Solid Films 515 (2007), M.S. Kartavtseva et al. BiFeO 3 thin films prepared by MOCVD. Surface & Coatings Technology 201 (2007), K. Momma and F. Izumi. VESTA 3 for three dimensional visualization of crystal, volumetric and morphology data. J. Appl. Cryst. 44, (2011).