Crystal Structure Analysis of Epitaxial BiFeO₃–BiCoO₃ Solid Solution Films Grown by Metalorganic Chemical Vapor Deposition

Abstract

Epitaxial (001)-oriented (1-x)BiFeO3–xBiCoO3 solid solution films with x = 0–0.33 were grown on (100)SrTiO3 substrates at 700 °C by metalorganic chemical vapor deposition. The crystal structure of the films was characterized by high-resolution X-ray diffraction analysis and Raman spectroscopy. Unit cell volume and the lattice parameter were changed with increasing x. The BiFeO3 film with x = 0 has rhombohedral symmetry and those with x = 0.16 and 0.21 have a mixture of rhombohedral and tetragonal symmetries. Finally, tetragonal symmetry was observed for the film with x = 0.33 together with a small amount of the contamination phase. This result suggests that the symmetry of (1-x)BiFeO3–xBiCoO3 films changed from rhombohedral to tetragonal with increasing x similarly to Pb(Zr,Ti)O3 having a large piezo response.