Ferroelectricity of ultrathin ferroelectric Langmuir–Blodgett polymer films on conductive LaNiO3 electrodes

LaNiO3 (LNO) films with a surface roughness rms of 0.384nm and a sheet resistance of about 200Ω were prepared on SrTiO3 and Si/SiO2 substrates respectively by rf magnetron sputtering technique. The surface of LNO on Si/SiO2 substrate is smoother than that on SrTiO3 substrate. A nominal 2-monolayer (ML) poly(vinylidenefluoride-trifluoroethylene) film with a thickness of about 3nm was deposited on LNO coated Si/SiO2 substrate by Langmuir–Blodgett (LB) technology. Piezoresponse force microscopy (PFM) measurements 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.