Ferroelectricity of ultrathin ferroelectric Langmuir-Blodgett polymer films on conductive LaNiO_3 electrodes

摘要

LaNiO_3 (LNO) films with a surface roughness rms of 0.384 nm and a sheet resistance of about 200 Ω were prepared on SrTiO_3 and Si/SiO_2 substrates respectively by rf magnetron sputtering technique. The sur face of LNO on Si/SiO_2 substrate is smoother than that on SrTiO_3 substrate. A nominal 2-monolayer (ML) poly(vinylidenefluoride-trifluoroethylene) film with a thickness of about 3 nm was deposited on LNO coated Si/SiO_2 substrate by Langmuir-Blodgett (LB) technology. Piezoresponse force microscopy (PFM) measure ments show that the LB films demonstrate an obvious feature of polarization switching and good voltage durability. The results suggest that the ultrathin polymer films may be utilized to explore ferroelectric tunnel junctions.