Stabilization of mixed-phase structures in highly strained BiFeO3 thin films via chemical-alloying

Chemical-alloying is demonstrated to stabilize the mixed-phase structure of highly strained epitaxial BiFeO3/LaAlO3 (001) heterostructures. Such mixed-phase structures are essential for the large electromechanical responses (4%-5% strains under applied electric field); however, films with thickness exceeding 250nm undergo an epitaxial breakdown to a non-epitaxial bulk-like rhombohedral-phase. Such an irreversible transformation of the mixed-phase structure limits the magnitude of the net surface displacement associated with these field-induced phase transformations. Using high-resolution x-ray diffraction reciprocal space mapping and scanning-probe-based studies, we show that chemical-alloying of BiFeO3 thin films can stabilize these mixed-phase structures and delay the onset of epitaxial breakdown. (C) 2012 American Institute of Physics. [doi:10.1063/1.3688175]