Fabrication of (100)_c-oriented Mn-doped bismuth ferrite films on silicon and stainless steel substrates using calcium niobate nanosheets

抄録

One-axis-oriented BiFeO₃ (BFO)-based films were fabricated on platinized silicon and SUS 316L substrates using nanosheets of calcium niobate (ns-CN) with pseudo-perovskite crystal structure. Ca₂Nb₃O₁₀ nanosheets (ns-CNs) were supported on the substrates by dip coating, followed by chemical solution deposition (CSD) of Mn-doped BFO (Mn-BFO) films. Preferential crystal growth of (100)-oriented BFO films was achieved on both ns-CN/(111)Pt/TiO₂/(100)Si and ns-CN/(111)Pt/SUS316L substrates. The out-of-plane lattice parameters of the BFO films on ns-CN/(111)Pt/SUS316L were larger than the parameter reported for BFO bulk because of elastic deformation caused by thermal stress between the BFO films and SUS316L substrate, whereas those of the films on ns-CN/(111)Pt/TiO₂/(100)Si were smaller than the reported value. The remanent polarization of the Mn-BFO films was enhanced to approximately 60 µC/cm² on ns-CN/(111)Pt/SUS316L because of the compressive thermal stress that causes elastic elongation of Mn-BFO crystals to align or change the tilt angle of their polar axes for the substrate surface.