"Negative capacitance" in resistor-ferroelectric and ferroelectric-dielectric networks: Apparent or intrinsic?
"Negative capacitance" in resistor-ferroelectric and ferroelectric-dielectric networks: Apparent or intrinsic?
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DOI：
10.1063/1.5016152
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发表时间：
2018-03-14
影响因子：
3.2
通讯作者：
Gupta, Sumeet K.
中科院分区：
文献类型：
--
作者：
Saha, Atanu K.;Datta, Suman;Gupta, Sumeet K.
在本文中，我们描述和分析证实了铁电体（FE）中负电容（NC）效应的另一种解释。我们声称先前在电阻-铁电（R-FE）网络中证明的NC效应并不一定证明极化和电压之间存在“S”形关系（根据朗道理论）。事实上，NC效应可以在不调用有限元的“S”形行为的情况下解释。我们采用了FE的解析模型（Miller模型），其中稳态极化随FE上的电压严格增加，并表明尽管固有的正FE电容，但在R-FE网络以及铁电介质（FE- de）堆栈中，FE电压随电荷的增加而降低是可能的。这可以归因于矫顽力电压附近FE电容的大量增加，以及相对于电场的极化滞后。在一定条件下，这两个因素产生瞬态NC效应。我们解析地导出了在R-FE和FE-DE网络中NC效应的条件。我们将我们的分析与广泛的模拟相结合，以解释NC效应的演变。我们还比较了上述Miller模型与Landau-Khalatnikov （L-K）模型（由于“S”形行为导致的静态负电容）预测的趋势，并强调了两种方法之间的差异。首先，随着R-FE网络外部电阻的增加，NC效应在Miller模型下表现为非单调行为，而在L-K模型下表现为增加。其次，随着FE-DE堆叠中外加电压斜坡率的增加，Miller模型的NC效应增大，L-K模型的NC效应减小。这些结果为实验验证有限元中NC效应的实际原因提供了一种可能的方法。AIP出版社出版。
In this paper, we describe and analytically substantiate an alternate explanation for the negative capacitance (NC) effect in ferroelectrics (FE). We claim that the NC effect previously demonstrated in resistance-ferroelectric (R-FE) networks does not necessarily validate the existence of "S" shaped relation between polarization and voltage (according to Landau theory). In fact, the NC effect can be explained without invoking the "S"-shaped behavior of FE. We employ an analytical model for FE (Miller model) in which the steady state polarization strictly increases with the voltage across the FE and show that despite the inherent positive FE capacitance, reduction in FE voltage with the increase in its charge is possible in a R-FE network as well as in a ferroelectric-dielectric (FE-DE) stack. This can be attributed to a large increase in FE capacitance near the coercive voltage coupled with the polarization lag with respect to the electric field. Under certain conditions, these two factors yield transient NC effect. We analytically derive conditions for NC effect in R-FE and FE-DE networks. We couple our analysis with extensive simulations to explain the evolution of NC effect. We also compare the trends predicted by the aforementioned Miller model with Landau-Khalatnikov (L-K) model (static negative capacitance due to "S"-shape behaviour) and highlight the differences between the two approaches. First, with an increase in external resistance in the R-FE network, NC effect shows a non-monotonic behavior according to Miller model but increases according to L-K model. Second, with the increase in ramp-rate of applied voltage in the FE-DE stack, NC effect increases according to Miller model but decreases according to L-K model. These results unveil a possible way to experimentally validate the actual reason of NC effect in FE. Published by AIP Publishing.