Mechanisms of extrinsic and intrinsic switching phenomena in ferroelectrics are explained and existing models are summarized. Then, criteria for an experimental distinction between both models are elaborated. Samples with thicknesses ranging from 2.7 to 63.8 nm prepared by a Langmuir–Blodgett technique were investigated with respect to these criteria. Measurements of their polarization switching behaviour, their polarization hysteresis loops, and their coercive fields were carried out. It is found that the coercive fields increase with decreasing sample thickness. Also, the switching time increases with decreasing sample thickness and it increases with decreasing field strength. The switching process turns out to be thermally activated. We find that neither intrinsic nor extrinsic models are sufficient to describe the experimental situation.

In addition to our previous work, we report on further experimental results concerning Langmuir–Blodgett polyvinylidenefluoride-copolymer thin films. Polarization hysteresis loops and polarization switching behaviour of samples with thicknesses below 3 nm were measured. Also, the time and temperature comportments of the remanent polarization were investigated for various film thicknesses, ranging from 2.7 up to 63.8 nm. The remanent polarization shows a loss of about 10% over 3 decades of time, ranging from 100 to 2 · 105 s. For thinner films, the remanent polarization exhibits the typical behaviour of a first-order transition, whereas for thicker samples a diffuse transition is found. Initial polarization curves obtained from the unpolarized state were finally measured. They are temperature and thickness dependent.

Langmuir-Blodgett (LB) films are well known structures prepared as a result of successive transfer of monolayers (ML) from the gas-liquid interface onto solid substrates. One impressive possibility of LB method is the opportunity to vary the thickness of the film to an accuracy of one transfer, which could coincide with one ML. The ferroelectric properties of a copolymer of vinylidene fluoride and trifluorethylene P[VDF-TrFE] prepared by LB deposition are investigated in the region of a few monolayers.

Metal-insulator-semiconductor structures with thin films of the ferroelectric copolymer poly(vinylidene fluoride trifluoroethylene) on oxidized n-silicon exhibit negative capacitances, i.e., inductivelike behavior. The magnitude of negative capacitances depends besides on the layer properties also on frequency and bias. Additional time domain measurements confirm the inductive character. A qualitative model for this behavior based on space charge limited currents is briefly discussed.

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