Thermodynamic modeling of critical properties of ferroelectric superlattices in nano-scale
Thermodynamic modeling of critical properties of ferroelectric superlattices in nano-scale
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DOI：
10.1007/s00339-009-5261-8
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发表时间：
2009-05
期刊：
影响因子：
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通讯作者：
Yue Zheng;C. Woo
中科院分区：
文献类型：
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作者：
Yue Zheng;C. Woo
使用朗道自由能泛函方法对纳米级铁电超晶格进行建模需要结合界面效应和去极化场效应的贡献。阶次参数的选择就成为一个至关重要的问题。在本文中，我们比较了使用自发极化作为序参数的模型（SPOP 方法）和使用总极化作为序参数的模型（TPOP 方法）的预测。我们使用这两种方法全面计算了纳米级铁电超晶格的关键性质，例如相变温度、临界厚度和居里-韦斯型关系。我们发现，在本文研究的所有案例中，所有 SPOP 结果都与实验测量和第一原理计算非常一致。另一方面，TPOP 方法通过低估电介质屏蔽的影响而大大高估了去极化，并产生与实验结果显着偏差的结果。我们的结果还追踪了铁电超晶格组成层厚度的关键特性与界面和去极化场效应的依赖性。
Modeling nano-scale ferroelectric superlattices using the Landau free-energy functional approach requires incorporating contributions from the interfacial and depolarization field effects. The choice of the order parameter then becomes a vital issue. In this paper, we compare the predictions of models using the spontaneous polarization as order parameter (SPOP approach) with models using the total polarization as order parameter (TPOP approach). We have comprehensively calculated the critical properties of nano-scale ferroelectric superlattices, such as the phase-transition temperature, critical thickness and Curie–Weiss-type relation using both approaches. We found that all the SPOP results are in excellent agreement with experimental measurements and first-principle calculations in all cases studied here. The TPOP approach, on the other hand, much overestimates the depolarization by underestimating the effect of the dielectric screening and produces results that deviate significantly from the experimental ones. Our results also traced the dependence of the critical properties on the thicknesses of the constituent layers of the ferroelectric superlattices to the interfacial and depolarization field effects.