Polarization Reversal Model and Prediction of Temperature-Dependent Switching of Ferroelectric Capacitors
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Polarization Reversal Model and Prediction of Temperature-Dependent Switching of Ferroelectric Capacitors Igor Stolichnov, Alexander K. Tagantsev and Nava Setter Ceramic Laboratory, Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland Jeffrey S. Cross Fujitsu Laboratories, Ltd., 10-1 Morinosato-wakamiya, Atsugi, 243-0197 Japan ABSTRACT
Temperature dependent performance of ferroelectric non-volatile memories is an important issue, that impacts memory device reliability. In general, the device temperature strongly influences the speed of polarization reversal in ferroelectric capacitors. In particular, the switching speed decreases with the decreasing temperature, which may give rise to incomplete switching. In the present work, the recently proposed Nucleation-Limited Switching model for ferroelectric thin films is extended for description of the temperature dependence of the polarization reversal. The model is shown to be valid for the temperature range important for memory applications. This model enables quantitative prediction of the switching performance of ferroelectric capacitors at different temperatures based upon results obtained at room temperature. The temperature and voltage range where the proposed concept is applicable is discussed in context of limits of validity of the Nucleation-Limited Switching model.
INTRODUCTION Temperature dependence of the switching behavior of ferroelectric thin films is an important issue for a wide range of applications including ferroelectric memory devices. To understand and predict the switching behavior of ferroelectric films under different circumstances one needs a comprehensive model that describes the switching process as a function of voltage, time and temperature. For the moment, the most developed and widely accepted theory describing the switching kinetics in ferroelectrics is that forwarded by the group of Isibashi [1]. This theory enables a correct description of switching kinetics in ferroelectric bulk materials however, encounters difficulties when applied to the thin films [2, 3]. For description of the switching kinetics in thin films the authors recently proposed an alternative concept [3] called hereafter the Nucleation-Limited Switching (NLS) model, which describes adequately the switching process in thin films for a wide range of switching times and applied voltages. The present paper extends this model in order to describe the temperature dependence of polarization reversal and demonstrates that the model can be used for prediction of the switching performance at different temperatures based on the room-temperature data. For the experimental verification of the model the polarization switching curves of PLZT films are studied at different temperatures and compared with the model predictions.
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NUCLEATION-LIMITED SWITCHING MODEL FOR DIFFERENT TEMPERATURES The NLS model describes the fraction of reversed polarization as a function of time and switching voltage under the following key assumptions discussed in detail elsewhe
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