Ultrathin ferroelectric polymer films

We have established ferroelectric switching and observed a novel conductance switching phenomenon in the first ultrathin ferroelectric polymer films fabricated by the Langmuir-Blodgett technique. The films consist of up to thirty monolayers of a copolymer of vinylidene fluoride (70%) and trifluoroethylene (30%) and exhibit classic ferroelectric behavior, including a first-order ferroelectric phase transition, polarization reversal (switching), thermal hysteresis of the capacitance, field-dependent switching dynamics, pyroelectricity, and piezoelectricity. The results of polarization, capacitance, switching, spectroscopic, and pyroelectric measurements on these highly crystalline and fully oriented films provide unprecedented detail concerning the thermodynamic properties of the ferroelectric and nonferroelectric states in ultrathin polymer films. The electric field and the film thickness have a strong influence on the ferroelectric properties.