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The temperature dependences of the polarization switching properties of Bi3.15Nd0.85Ti3O12 (BNT) ferroelectric thin film in the range from 25 to 150°C have been investigated. With increasing temperature, the switchable polarization and switching time decrease. Meanwhile, the depolarization field due to the interfacial layer between the electrode and the BNT film increases with increasing temperature, which induces more domain back-switching. In addition, the local switching properties of BNT film have been studied using piezoresponse force microscopy, and it is found that the prepared BNT film has good local switching behaviors. [ABSTRACT FROM AUTHOR]

A model for the electric displacement hysteresis and strain butterfly loops of ferroelectric films under electrical loading is proposed based on an improved Preisach model for nonlinear remanent polarization. Our model shows improved displacement and strain versus electric field loops that agree reasonably well with the experimental data. Compared to the previous model, the current model, including the history-dependent electric field effect, which is always neglected in the conventional model, provides electric displacement and strain loops with a full and symmetric shape. In addition, both the loops of electric displacement and strain under intrinsic defects and injected charges have also been investigated by our model. [ABSTRACT FROM AUTHOR]

Modeling of the hysteresis loop of ferroelectric thin films has been thought very difficult owing to its nonlinear and history-dependent electric field effects. Here we extend the Preisach model [Z. Phys. 94, 277 (1935)] by using the distribution function integral and superposition method. The model shows improved hysteresis loop that agrees reasonably well with the experimental data measured from the bismuth layer-structured ferroelectric thin films. Compared with the previous model, the current model provides polarization-field (P-E) loop with full and symmetric shape, suitable coercive field (Ec), and few undesirable parameters. The butterfly loop of perovskite-type ferroelectric thin films is also simulated. Additionally, the approach is able to describe the unsaturated loops obtained under various ac electric fields, which is very useful in circuit simulation of ferroelectric field effect transistor or ferroelectric capacitor. [ABSTRACT FROM AUTHOR]

In this work, metal-ferroelectric-insulator-semiconductor (MFIS) structure capacitors with SrBi2 Ta2O9 (300nm) as ferroelectric thin film and HfTaO (6nm, 8nm, 10nm, and 12nm) as insulating buffer layer were proposed and investigated. The prepared capacitors were fabricated and characterized before radiation and then subjected to 60Co gamma irradiation in steps of two dose levels. Significant irradiation-induced degradation of the electrical characteristics was observed. The radiation experimental results indicated that stability and reliability of as-fabricated MFIS capacitors for nonvolatile memory applications could become uncontrollable under strong irradiation dose and/or long irradiation time. [ABSTRACT FROM AUTHOR]

The interface effects on the ferroelectric polarization and stability of PbTiO3 (PTO) films with metallic (Pt) or oxide (LaNiO3, SrRuO3) electrodes were studied using density functional theory calculation. It was found that the PTO film with oxide electrodes has stronger electrode/ferroelectric interface adhesion, lower polarization magnitude, and worse polarization stability, than that with Pt electrode. The PbO-terminated PTO films show weaker adhesion with the electrodes, but have higher polarization magnitude and better polarization stability than the TiO2-terminated ones. The strain effects induced by misfit interface were also studied. Results show that the ferroelectric polarization and its stability can be enhanced by applying compressive strain, while depressed by applying tensile strain. [ABSTRACT FROM AUTHOR]

A phase field model based on the time-dependent Ginsburg-Landau equation is developed to investigate the space charge distribution effects on the ferroelectric hysteresis characteristics of the ferroelectric thin film, in which the inhomogeneity of the built-in electric field (Eib) distribution along the vertical direction of ferroelectric thin film and the corresponding effect on the domain kinetics are taken into account. The hysteresis loops of the ferroelectric thin films with different space charge distributions are calculated by using this model. The results indicate that symmetrically (including homogeneously) distributed space charges lead to the hysteresis loop constriction because the Eib weakens the total electric field to make the ferroelectric film form a stable monodomain structure or the 180° strip domain. However, asymmetrically distributed space charges cause not only the shift but also the distortion of the hysteresis loop which is pinched in one head and loses its centrosymmetry. This is attributed to that the negative Eib changes the total electric field and activates domain nucleation at the interface. [ABSTRACT FROM AUTHOR]

The metal-ferroelectric-insulator-semiconductor (MFIS) structure diodes with SrBi2Ta2O9 (SBT) as ferroelectric thin film and HfO2 as insulating buffer layer were fabricated. The electrical properties of MFIS structure were investigated for different HfO2 buffer layer thickness. The experimental results show that the memory window extended significantly as the HfO2 layer thickness increased from 6 to 10 nm. It is also observed that the leakage current was reduced to about 10-10 A at applied voltage of 4 V, and the high and low capacitances remained distinguishable for over 8 h even if we extrapolate the measured data to 10 years. [ABSTRACT FROM AUTHOR]

Incorporating the vacancy electromigration theory into the switching-induced charge-injection mechanism into the local phase decomposition model has led to an analytical model for the dielectric fatigue behavior and the remnant polarization in perovskite structured ferroelectric thin films. The model has allowed us to reproduce the fatigue behavior in various ferroelectric thin films measured under different voltages, temperatures, and frequencies. We concluded the essential reason for electrical fatigue in ferroelectrics is the local phase separation induced directly or indirectly by other fatigue mechanisms proposed in previous papers. [ABSTRACT FROM AUTHOR]

The anomalous vertical shift behavior of hysteresis loops observed in compositionally graded ferroelectric films was investigated using an analytical bilayer model. By introducing a parameter A which is defined by grad(c)/c(0), the model demonstrated that the compositional graded structure is sufficient to allow for the hysteresis loop shift along the polarization axis, and the shift is affected significantly by the concentration distribution in the films. Two reversed electric field buildups were also observed in the layers as indicated by the E-t profile. [ABSTRACT FROM AUTHOR]

The effects of europium (Eu) content on the microstructure, fatigue endurance, leakage current density, and remnant polarization (2Pr) of Bi4-xEuxTi3O12 (BET) thin films prepared by metal-organic decomposition method at 700 °C annealing temperature were studied in detail. The results showed that 2Pr (82 μC/cm2 under 300 kV/cm), fatigue endurance (2% loss of 2Pr after 9.0×109 switching cycles), and leakage current density (1×10-8 A/cm2 at 200 kV/cm) of BET thin film with x=0.85 are better than those of thin films with other contents. Additionally, the mechanism concerning the dependence of ferroelectric properties on Eu content was discussed. [ABSTRACT FROM AUTHOR]

The strain, inevitably existing in ferroelectric films and devices, is an important factor for determining their polarization properties and performances. It requires an understanding of the effects of strain on polarization dynamics of ferroelectric film. Considering the strain effect, an analytic thermally activated electric polarization-switching model was developed for the study of the polarization properties of ferroelectric films. Using this model, we successfully simulated the time dependent polarization reversal, the coercive field, the polarization switching time, and the polarization hysteresis loops as a function of the lattice mismatch, external applied stress, applied electric field, and temperature. Theoretical predications of the model are in good agreement to experimental observations and they reinforce the possibility of using sophisticated thin film fabrication techniques such as lattice mismatch strain to engineer ferroelectric thin films structures and devices with controlled properties. Our study offers clear analytical relations that can be easily used in future studies of ferroelectrics. [ABSTRACT FROM AUTHOR]

Investigates the interfacial fracture energy of PZT ferroelectric thin films by nano-scratch technique. Assessment of the failure characteristic of PZT thin film; Spallation of the film in the nano-scratch; Interfacial adhesion of PZT thin films.