Polarization suppression in Pb(Zr,Ti)O3 thin films

Abstract

Switchable polarization can be suppressed in Pb(Zr,Ti)O3 thin films by optical, thermal, electrical, and reducing processes. The optical suppression effect occurs by biasing the ferroelectric near the switching threshold and illuminating the material with band gap light; the thermal suppression effect occurs by biasing the ferroelectric near the switching threshold and heating the material to ≊100 °C. The electrically induced suppression effect, known as electrical fatigue, occurs by subjecting the ferroelectric capacitor to repeated polarization reversals. We find that the suppressed polarization in these three cases can be restored to essentially its initial polarization value by creating electronic charge carriers in the ferroelectric. This strongly suggests that all three forms of degradation largely involve locking domains by electronic charge trapping at domain boundaries. The fourth form of polarization suppression, a reducing treatment, was obtained by annealing the crystallized PZT films at 400 °C in nitrogen. The suppressed polarization could not be restored by injecting electronic charge into the reduced films, indicating that the mechanism for polarization suppression is different. In this case, it appears as though ionic defects, such as oxygen vacancies, are responsible for locking the domains, and hence, suppressing the polarization.

Scaling of structure and electrical properties in ultrathin epitaxial ferroelectric heterostructures

“…It could be surmised that the presence of ionic defects ͑e.g., oxygen vacancies͒ or electronic charge carriers could possibly lead to elongated lattice parameters 54 or would pin domain walls 55,56 and therefore reduce the measured switchable polarization. While we cannot fully neglect the effect of oxygen vacancies, generally such ionic vacancies are expected to increase leakage currents dramatically.…”

Residual stress relief due to fatigue in tetragonal lead zirconate titanate ceramics

“…On the other hand, the term ageing normally refers to a timedependent decay of the dielectric and piezoelectric properties in the absence of any external stimulus. 4 Several different mechanisms have been identified as the origin of fatigue in ferroelectrics; these include microcrack growth and coalescence due to internal residual stresses, 5,6 space charge formation, 2 and point defect clustering. [7][8][9] The development of fatigue depends on a variety of factors such as the nature of the load (electrical, mechanical), 9,10 type of waveform (unipolar, bipolar, sesquipolar), 11,12 frequency, 13 the chemical composition and structure/microstructure of the material, 14 and other environmental factors such as temperature.…”

“…[1][2][3] In this context, the term fatigue is usually employed to describe changes in the functional properties over time as a result of static or alternating electrical and mechanical loads. On the other hand, the term ageing normally refers to a timedependent decay of the dielectric and piezoelectric properties in the absence of any external stimulus.…”

Fractal cluster modeling of the fatigue behavior of lead zirconate titanate

“…5,6 Previous studies have shown that planar ordering of oxygen vacancies occurs in perovskites with an increase in defect density, [7][8][9][10][11] with a minority of vacancies remaining as uncorrelated point defects. Reflection highenergy electron diffraction studies by Matsumoto et al 12 of SrTiO 3 have shown that oxygen vacancies form a superstructure on a nanometer scale, further confirming the hypothesis that oxygen vacancies in pervoskites form an ordered network. With an increase in concentration, oxygen vacancies cluster, initially in one-dimensional ͑1D͒ chains and above a certain density in planes of specific geometries.…”