Crystal structure and electrical properties of {100}-oriented epitaxial BiCoO₃-BiFeO₃ films grown by metalorganic chemical vapor deposition

_xBiCoO₃-(1- x)BiFeO₃ (x = 0-0.22) films of 400 nm thickness were grown on (100)_c SrRuO₃ ∥ (100) SrTiO₃ substrates by metalorganic chemical vapor deposition. The changes in the crystal structure and electrical properties of the films with x were investigated. The constituent phase changed from rhombohedral to a mixture of rhombohedral and tetragonal, and to tetragonal with increasing x, but the x for this transition is different from that of 200-nm-thick films grown on (100) SrTiO₃ substrates. The x of the morphotropic phase boundary that consisted of a mixture of tetragonal and rhombohedral symmetries depended on the film thickness. The remanant polarization continuously decreased with increasing x, in good agreement with the results obtained with the {100}-oriented Pb(Zr,Ti)O₃ epitaxial films owing to the decrease in the crystal anisotropy of the films.