The Concept of Negative Capacitance in Ionically Conductive Van der Waals Ferroelectrics,Advanced Energy Materials

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The Concept of Negative Capacitance in Ionically Conductive Van der Waals Ferroelectrics
Advanced Energy Materials ( IF 24.4 ) Pub Date : 2020-09-03 , DOI: 10.1002/aenm.202001726
Sabine M. Neumayer ₁ , Lei Tao _{2,

3} , Andrew O'Hara ₂ , Michael A. Susner ₄ , Michael A. McGuire ₅ , Petro Maksymovych ₁ , Sokrates T. Pantelides _{2,

6} , Nina Balke ₁

Affiliation

Negative capacitance (NC) provides a path to overcome the Boltzmann limit that dictates operating voltages in transistors and, therefore, may open up a path to the challenging proposition of lowering energy consumption and waste heat in nanoelectronic integrated circuits. Typically, NC effects in ferroelectric materials are based on either stabilizing a zero‐polarization state or slowing down ferroelectric switching in order to access NC regimes of the free‐energy distribution. Here, a fundamentally different mechanism for NC, based on CuInP₂S₆, a van der Waals layered ferrielectric, is demonstrated. Using density functional theory and piezoresponse force microscopy, it is shown that an unusual combination of high Cu‐ion mobility and its crucial role in determining polarization magnitude and orientation (P) leads to a negative slope of the polarization versus the electric field E, dP/dE < 0, which is a requirement for NC. This mechanism for NC is likely to occur in a wide class of materials, offering new possibilities for NC‐based devices. The nanoscale demonstration of this mechanism can be extended to the device‐level by increasing the regions of homogeneous polarization and polarization switching, for example, through strain engineering and carefully selected electric field pulses.

中文翻译：

离子导电范德华铁电体中的负电容概念

负电容（NC）提供了一条克服玻耳兹曼极限的途径，该极限决定了晶体管的工作电压，因此可以为降低纳米电子集成电路中的能耗和废热这一具有挑战性的主张开辟一条道路。通常，铁电材料中的NC效应是基于稳定零极化状态或减慢铁电开关的速度，以便获得自由能分布的NC机制。在这里，基于CuInP ₂ S _6的NC的根本不同的机制展示了范德华分层铁电体。使用密度泛函理论和压电响应力显微镜，表明高Cu离子迁移率及其在确定极化幅度和方向（P）中的关键作用的异常组合导致极化相对于电场E，dP的负斜率/ dE <0，这是NC的要求。这种用于NC的机制很可能会出现在各种各样的材料中，这为基于NC的设备提供了新的可能性。通过增加均匀极化和极化切换的区域，例如通过应变工程和精心选择的电场脉冲，可以将该机制的纳米级演示扩展到设备级。

更新日期：2020-10-20

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