Influence of ex-situ thermal treatment on the chemical states, microstructure and ferroelectrics properties of polycrystalline BiMnO3-? thin films

Nanoelectronic devices based on oxide films require materials that may exhibit combined properties such as ferroelectricity, ferromagnetism, and/or ferroelasticity at the same phase. In this sense, multiferroic perovskite BiMnO3-6 thin films exhibit a relevant combination of ferroelectricity and ferromagnetism suitable for device applications. The purpose of this work is to investigate the growth conditions of BiMnO3 thin films using radiofrequency magnetron sputtering and the role of ex-situ thermal treatments under different conditions, which resulted in a P21/c to C2 phase transformation and BiMnO2.93 composition. The crystal structure of the BiMnO3-6 thin films was investigated using X-ray diffraction, high-resolution transmission electron microscopy, ultravioletvisible spectrophotometer, X-ray photoelectron spectroscopy, and resistivity measurement, to correlate structural and transport properties. The ex-situ thermal treatment was performed in a bismuth and oxygen atmosphere in order to compensate for Bi and O deficiencies. Thus, the result was not an ideal stoichiometric, BiMnO3-6 proved to enhance the ferroelectric properties and other physical properties. The optimized thin films exhibit ferromagnetism up to 37 K, while ferroelectricity remains up to room temperature.