S. V. Ryabtsev

Fatigue of Lead Titanate and Lead Zirconate Titanate Thin Films

The fatigue of lead titanate and lead zirconate titanate ferroelectric thin films, i.e., a change in the polarization as a function of the number of switching cycles in an external electric field, is investigated experimentally. The threshold numbers of switching cycles are determined to be 1010–1011 for the lead titanate films and 109–1010 for the lead zirconate titanate films. It is shown that a change in the temperature does not substantially affect the threshold number of switching cycles at which the switched polarization decreases drastically. However, an increase in the external field strength leads to a noticeable decrease in the threshold number of switching cycles. The process of fatigue is accompanied by an increase in the coercive field and the internal bias field. It is established that, as the number of switching cycles increases, the internal bias field changes more significantly as compared to the coercive field. The absence of a change in the phase composition in repeatedly switched samples indicates that the fatigue processes have a nonchemical nature. The anomaly observed in the frequency dependence of the permittivity in the frequency range 106–107 Hz due to the domain structure disappears after multiple switching cycles. This suggests that the observed fatigue phenomenon has a domain nature.

Dielectric properties of lead titanate thin films on corundum substrates

Ferroelectric films of lead titanate were synthesized on corundum (Al2O3) substrates. The main parameters that characterize the dielectric hysteresis, such as the spontaneous polarization, coercive force, internal bias field, and the phase-transition temperature, were determined. The dispersion of the permittivity was studied using impedance spectroscopy in wide temperature and frequency ranges. An anomaly in the frequency dependence of the complex permittivity was revealed at frequencies of the order of 107 Hz.

Processes of ageing and fatigue in lead titanate thin films

Processes of ageing and fatigue in lead titanate thin films are experimentally investigated. The films under discussion were synthesized by plasma-enhanced magnetron sputtering of titanium and lead on titanium, silicon and polycor substrates in an argon environment, and subsequent annealing in an oxygen atmosphere. High temperature resistance, long shelf ageing and repolarization stability of lead titanate films on polycor substrates was shown. Reduction of polarization under cyclic switching in sine wave electric field to the minimal value happens after 10 11 cycles. Partial recovery of the basic dielectric characteristics of lead titanate thin films was observed during relaxation without external influences.

Dielectric properties of thin PbTiO3 films

The electrophysical properties and phase composition of thin lead titanate films prepared on various substrates by layer-by-layer magnetron sputtering of metals followed by annealing have been studied. The main parameters of the metal-ferroelectric film-metal multilayer structures, namely, the spontaneous polarization, coercive field, and permittivity, were studied for various substrate types and electrode materials. The conditions favorable for the formation of PbTiO3 films that are similar in stoichiometry and phase composition were established.

Frequency dependence of the coercive field and the internal bias field in ferroelectric thin films

The dependences of the coercive field and the internal bias field on the switching field frequency for lead zirconate titanate and lead titanate thin films are experimentally studied over a wide temperature range. It is shown that, as the frequency increases, the coercive field and the bias field in these films increase at the rate dependent on the temperature and the substrate used.

Parameters of Domain Boundaries in Thin PbTiO3 Films

Features of polarization switching processes in lead titanate thin films were investigated. The films under discussion were synthesized by plasma-enhanced magnetron sputtering of titanium and lead on Al 2 O 3 substrates in an argon medium, and subsequent annealing in an oxygen atmosphere. In terms of theory of lateral motion of domain boundaries the main parameters of domain walls, characterizing kinetics of domain structure in thin polycrystalline lead titanate films, were determined.

Switching Frequency Dependence in Thin Films of Lead Titanate and Lead Zirconate Titanate

The dependencies of coercive field and internal bias field on the frequency of the applied external field were experimentally studied in the films of lead titanate and lead zirconate titanate in a wide temperature range. It was demonstrated that with the frequency increase in the above films a build up of coercive field and internal bias field is observed, the rate of which depends on the temperature. The nature of the above phenomenon was analyzed and its relation to activation processes accompanying switching in ferroelectrics was shown.

Electrical properties of thin lead titanate films on polycor substrates

The dielectric properties of synthesized films, including the permittivity dispersion, have been investigated. The fatigue processes in the films have been experimentally studied as a function of the number of cycles of external voltage switching. It is established that the main dielectric characteristics are partially recovered in the absence of external actions.

Dispersion of Dielectric Permittivity in Thin Ferroelectric Lead Titanate Films

Lead titanate thin films were obtained by plasma-enhanced magnetron sputtering. Synthesized films demonstrate high temperature stability, relatively narrow maximum at temperature of phase transition for ε (T ) dependence, great dielectric constant value near the Curie point, saturated hysteresis loops, and relaxation character for dispersion of dielectric permittivity similar to bulk samples.