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首页> 外文期刊>Physical review >Understanding the origins of the intrinsic dead layer effect in nanocapacitors
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Understanding the origins of the intrinsic dead layer effect in nanocapacitors

机译:了解纳米电容器本征死层效应的起源

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Thin films of high-permittivity dielectrics are considered ideal candidates for realizing high charge-density nanosized capacitors for use in next generation energy storage and nanoelectronic applications. The experimentally observed capacitance of such film nanocapacitors is, however, 1 order of magnitude lower than expected. This dramatic drop in capacitance is attributed to the so-called "dead layer"-a low-permittivity layer at the metal-dielectric interface in series with the high-permittivity dielectric. The exact nature of the dead layer and the reasons for its origin still remain somewhat unclear. Based on insights gained from recently published ab initio work on SrRuO_3/SrTiO_3/SrRuO_3 and our first-principles simulations on Au/MgO/Au and Pt/MgO/Pt nanocapacitors, we construct an analytical model that isolates the contributions of various physical mechanisms to the intrinsic dead layer. In particular we argue that strain-gradients automatically arise in very thin films even in absence of external strain inducers and, due to flexoelectric coupling, are dominant contributors to the dead layer effect. Our theoretical results compare well to existing as well as our own ab initio calculations and suggest that inclusion of flexoelectricity is necessary for qualitative reconciliation of atomistic results. Our results also hint at some remedies for mitigating the dead layer effect.
机译:高介电常数电介质薄膜被认为是实现用于下一代能量存储和纳米电子应用的高电荷密度纳米电容器的理想选择。然而,这种膜纳米电容器的实验观察到的电容比预期的低1个数量级。电容的急剧下降归因于所谓的“死层”,即与高介电常数电介质串联的金属-介电界面处的低介电常数层。死层的确切性质及其起源的原因仍不清楚。基于从最近发表的有关SrRuO_3 / SrTiO_3 / SrRuO_3的从头开始的工作以及我们对Au / MgO / Au和Pt / MgO / Pt纳米电容器进行的第一性原理模拟所获得的见解,我们构建了一个分析模型,该模型将各种物理机制对本征死层。特别是,我们认为即使在没有外部应变感应器的情况下,应变梯度也会在非常薄的薄膜中自动出现,并且由于柔电耦合,是导致死层效应的主要因素。我们的理论结果与现有的以及我们自己的从头算相符,并且表明,对于原子性结果的定性和解,必须包含柔电。我们的结果还暗示了一些缓解死层效应的补救措施。

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