Multiferroic h-LuFeO₃ Thin Films on (111) and (100) Surfaces of YSZ Substrates: An Experimental and Theoretical Study

Abstract

Thin films of in-bulk unstable multiferroic hexagonal LuFeO 3 were synthesized on coherent (111) and for the first time on incoherent (100) YSZ and Pt/ YSZ surfaces by the metal−organic chemical vapor deposition (MOCVD) technique. The obtained films were thoroughly studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), atomic force microscopy (AFM), piezoresponse force microscopy (PFM), and theoretical simulations. The substrate surface symmetry has a crucial role in the formation of the epitaxial film's structure. Also, the molecular mechanics calculations were adapted for film/substrate interface simulation and, for the first time, the number of variants was predicted by the number of minima on the energy profile as well as it was proved that that the formation of h-LuFeO 3 is more energetically preferable than o-LuFeO 3 , even on the incoherent surface. It was shown that h-LuFeO 3 films deposited on the YSZ(111) surface have formed a single in-plane rotational variant structure, while those deposited on the YSZ(100) surface have formed a bivariant structure. PFM results of bivariant h-LuFeO 3 (001)//Pt(111)//YSZ(100) show half the size of ferroelectric domains (∼100 nm) and twice as large the values of piezoelectric response compared to h-LuFeO 3 (001)//Pt(111)//YSZ(111).

Single domain growth and charge ordering of epitaxial YbFe2O4 films

“…19,20 In addition, according to molecular dynamics simulation of the interface between hexagonal LuFeO3 and YSZ (111), the Fe 3+ ions were considered to have been placed directly on the O 2ion of oxygen-terminated surface. 39 Analogous to their results, the prospective atomic structures of the interface between YSZ (111) and YbFe2O4 (0001) are illustrated in Figure 6. On the oxygen terminated YSZ (111) substrate, the Fe-O layer in YbFe2O4 was coherently matched to the topmost Zr-O layer.…”

TSF-MOCVD – a novel technique for chemical vapour deposition on oxide thin films and layered heterostructures

“…It should be noted that epitaxial stabilization also changes the equilibrium characteristic phase relations between Fe 2 O 3 and LuFeO 3 : it is well known that in mixtures of powders of this and similar systems 6 a, c) indicate a higher uniformity and less surface roughness of the h-LuFeO 3 layer grown on YSZ(111) substrate compare to one deposited on YSZ(100). This observation can be explained by the previously described in-plane variant growth of h-LuFeO 3 on YSZ(100), which results in the formation of a films with microstructure fragmented into nanoscale domains [25]. The closer examination of images of heterostructure b-Fe 2 O 3 (001)//h-LuFeO 3 (001)//YSZ(100) revealed that h-LuFeO 3 had not formed located uniformly in one direction: its (001) planes were aligned parallel to both (001) and (111) planes of the YSZ substrate.…”

“…At the same time, in the heterostructure on the YSZ(100) substrate, b-Fe 2 O 3 grows in a different orientation relative to h-LuFeO 3 , which obviously leads to an increase in the critical thickness of this epitaxially stabilized layer. This interesting aspect, the dependence of the critical thickness on the orientetion of epitaxially stabilized phase, will be clarified by further calculations of the interface energies using the algorithm described by us in [25].…”

Synthesis of Sandwiched Composite Nanomagnets by Epitaxial Growth of Fe₃O₄Layers on Srfe₁₂o₁₉ Nanoplates in High-Boiling Organic Solvent

“…The lateral sides of the hexaferrite cores are free of magnetite, which indicates that the seeded growth of the spinel iron oxide occurs only on the spinel blocks of the hexaferrite structure, thus, the magnetite layers continue the hexaferrite structure. According to the results of HR-TEM with 2D FFT (Figure 2), HAADF STEM and SAED (Figure 3) the epitaxial relations between Fe3O4 and SrFe12O19 phases are following: The results of MD simulations based on the algorithm that was reported in [30], allowed us to propose the model of the interface that formed between Fe3O4 and SrFe12O19 phases (Figure 4). It should be noted that both SAED and simulation results yield the epitaxial relations that were stated above.…”