Effect of Film Thickness and Crystal Orientation on the Constituent Phase in Epitaxial BiFeO₃–BiCoO₃ Films Grown on SrTiO₃ Substrates

Abstract

The crystal symmetries of epitaxial (1-x)BiFeO3–xBiCoO3 films (x=0–0.46) grown on (100)SrTiO3, (110)SrTiO3, and (111)SrTiO3 substrates covered with/without SrRuO3 layers were systematically investigated as a function of film thickness and the crystal orientation of the substrates. Raman analysis was an effective method of crystal symmetry research on epitaxial BiFeO3–BiCoO3 films. Crystal symmetry was changed from being rhombohedral to tetragonal through the mixture of these symmetries with increasing BiCoO3 content irrespective of film thickness and the crystal orientation. However, the constituent phase was strongly depended on film and the crystal orientation of the substrates. The perovskite single phase was observed up to a higher x for the films grown on (100)SrTiO3 substrates than for those grown on (110)SrTiO3 and (111)SrTiO3 substrates. On the other hand, the constituent phase of the films grown on (111)SrTiO3 substrates was similar to that of the strain free powders obtained by high-pressure synthesis.

Enhanced Piezoelectric Constant of (1-x)BiFeO3–xBiCoO3 Thin Films Grown on LaAlO3 Substrate

“…BFCO thin films fabricated by chemical solution deposition (CSD) on a SrTiO 3 (STO) (001) single crystalline substrates exhibited a gradual second-order transition from rhombohedral to tetragonal phases at x ¼ 0:15{0:20. 19) This transition behavior is also reported by Yasui et al [20][21][22] Because of the lattice mismatch (the in-plane lattice parameter of the rhombohedral BFO is 1.15% larger than that of STO), BFO (x ¼ 0) relaxed from the STO substrate. The in-plane lattice parameter decreased with increasing Co content x, and the tetragonal x ¼ 0:30 film had no mismatch with the substrate.…”

Enhancement of phase stability and optoelectronic performance of BiFeO3thin filmsviacation co-substitution

“…The presence of secondary phases in the BiFeO 3 -BiCoO 3 system for cobalt concentrations up to 30% is attributed to the system instability, as previously reported in MOCVD samples . 45,46 In fact, pure BiCoO 3 is stable only at high pressure. 24 With the incorporation of La in BFCO30, the presence of secondary phases is suppressed and the (00l) reflections from La-BFCO30 sharpened, indicating the formation of pure phase epitaxial films with improved crystallinity.…”

Structure and Magnetic Properties of BiFe1–xCoxO3 and Bi0.9Sm0.1Fe1–xCoxO3

“…Some investigations have followed the PZT system, the solid solutions between rhombohedral BFO and tetragonal Bi based perovskite with a large c / a ratio, e.g., BiCoO 3 ( c / a = 1.267) − and BiZn 0.5 Ti 0.5 O 3 ( c / a = 1.211). , These studies are classified as B-site substitution of the perovskite oxide. Among them, a MPB with a √2 a × √2 a × a monoclinic Cm structure, where a was a lattice constant of a cubic perovskite that was essentially the same as that of PZT, was found in BiFe 1– x Co x O 3 with x ∼ 0.3 synthesized under high pressure. , In the vicinity of the MPB composition, the polarization vector of BiFe 1– x Co x O 3 rotates as a function of composition and temperature .…”