Fabrication and ferroelectric properties of BiFeO₃/LaNiO ₃ artificial superlattice structures grown by radio-frequency magnetron-sputtering

Symmetric superlattice structures of multiferroic BiFeO₃ and conductive LaNiO₃ sublayers were grown on a Nb-doped SrTiO ₃ substrate with radio-frequency magnetron-sputtering. The formation of a superlattice structure was confirmed from the appearance of satellite lines on both sides of the main line in the X-ray diffraction pattern. X-ray measurements show that these superlattice films become subject to greater tensile stress along the c-axis and to increased compressive stress parallel to the surface plane with a decreasing thickness of the sublayer. The smaller is the thickness of the sublayer, the greater is the crystalline quality and the strain state. The hysteresis loops show a large leakage current at frequencies of 0.5 and 1 kHz; the polarization decreases with an increasing frequency.