Fatigue of Pb(Zr0.53Ti0.47)O3 ferroelectric thin films

Abstract

Fatigue of Pb(Zr0.53Ti0.47)O3 ferroelectric thin films has been studied with several novel electrode modifications. Doped amorphous silicon is used as a gating layer between the ferroelectric and metal electrode to regulate the type of charge carrier injection during switching of the ferroelectric. This configuration requires a low switching frequency in order to avoid the relaxation effect that arises from the limited charging ability of the semiconductor. In addition, charge depletion in the semiconductor causes a polarization asymmetry that reflects a depolarization field due to incomplete compensation of the polarization charge. Fatigue tests reveal that electron injection is a necessary condition for polarization degradation, whereas hole injection is not. Blocking interfaces by SiO2 or c-oriented Bi4Ti3O12 can also mitigate fatigue, albeit at a reduced polarization level. On the other hand, compensation of Pb loss through PbO undercoat layer has little effect on fatigue. Based on these observations, injected electrons in association with oxygen vacancies generated during cycling are proposed as the defects responsible for fatigue. These defects may impede domain switching by segregation at the electrode interface or at domain boundaries, with an enhanced kinetics because of the lower valence of the partially de-ionized entity.

Microstructural evolution of charged defects in the fatigue process of polycrystalline BiFeO3 thin films

“…26 The activation energy of the defect in the sample_10 8 is estimated to be ~0.2 eV, which is however far below the value for the sample_fresh. Similar activation energy values have been reported and considered to originate from the following possibilities: 26,28 Upon polarization switching for 2×10 9 cycles, the corresponding ' ' M spectra of sample_2×10 9 is collected and shown in Figure 3c, which exhibits some new features. Below 120 o C, two partially overlapped peaks labeled I and II are observed in low frequency region (1-10 Hz) and higher frequency region (10-1000 Hz), respectively.…”

“…To clarify the role of defects involved during the cycling, the BFO thin films subjected to different numbers of switching cycles (labeled as sample_fresh, sample_10 8 and sample_2×10 9 ) were selected to investigate the relaxation behavior by monitoring their temperature-dependent impedance spectra. The ' ' M spectra obtained from the sample_fresh are shown in Figure 3a.…”

“…3 There is also a belief that the injected electrons from electrodes promote producing charged defects giving rise to fatigue failure by forming non-switching layers, local imprint or pinning the domain walls. [7][8][9] To properly understand the nature of the fatigue failure, there is a need to monitor the evolution of the fatigue-induced defects, which helps to develop fatigue-free ferroelectric capacitors for nonvolatile memory applications.…”

The Effect of Tungsten Trioxide Thin Films at Ferroelectric–Electrode Boundaries on Fatigue Behaviour

“…This contrasts with the Pt/PZT/WO 3 /Pt structure in that the time to fatigue appears to be almost independent of switching frequency. Such behavioural differences can be rationalized by consideration of charge injection ideas which have, for some time, been suggested to be one of the sources responsible for fatigue, [19][20][21] through the injection-associated formation of defects local to the ferroelectric-electrode boundaries. Several ideas for charge injection have been presented in recent literature.…”

Mechanism of polarization fatigue in BiFeO3: The role of Schottky barrier

“…There have been a large number of reports on the mechanism of the polarization fatigue. [2][3][4][5] The models proposed can generally be classified into three categories, namely charge injection, [6][7][8][9] defects, i.e. oxygen vacancies, redistribution [10][11][12][13][14] and local phase decomposition.…”