用于多功能神经形态电子学的单层石墨烯中的电子铁电性
Electronic ferroelectricity in monolayer graphene for multifunctional neuromorphic electronics
AI总结：
本研究通过石墨烯/h-BN界面的非对称莫尔超晶格在单层石墨烯中实现电子铁电性，并展示其在多态非易失存储和突触行为模拟中的应用。
摘要：
铁电性因其可由外电场切换的自发电极化而引人关注。将铁电材料拓展至二维极限将为下一代非易失器件的发展提供多种应用。传统铁电性要求材料至少由两种组成元素构成，并具有极性晶体结构。单层石墨烯作为一种元素二维材料，由于其高度中心对称的六角晶格，不太可能呈现铁电序。然而，二维莫尔超晶格为在非极性材料中调控多种电子序提供了强有力的方法。在此，我们通过在石墨烯/h-BN界面引入非对称莫尔超晶格，报道了在单层石墨烯中观测到电子铁电性。利用霍尔测量，电极化被确定源于电子-空穴偶极子，表明所观测铁电性的电子动力学特性。我们实现了标准的极化-电场磁滞回线，以及非常规的多个可切换极化态。通过与对照器件进行原位比较，我们发现石墨烯莫尔体系中的电子铁电性与石墨烯层数及相应的精细能带结构无关。此外，我们展示了这种铁电莫尔结构在多态非易失数据存储以及模拟多种突触行为方面的应用，包括短时程可塑性、长时程增强和长时程抑制。本工作不仅丰富了对铁电性的基础理解，还展示了石墨烯在多态存储器和神经形态计算中的广阔应用前景。
英文摘要：
Ferroelectricity is intriguing for its spontaneous electric polarization, which is switchable by an external electric field. Expanding ferroelectric materials to two-dimensional limit will provide versatile applications for the development of next-generation nonvolatile devices. Conventional ferroelectricity requires the materials consisting of at least two constituent elements associated with polar crystalline structures. Monolayer graphene as an elementary two-dimensional material unlikely exhibits ferroelectric order due to its highly centrosymmetric hexagonal lattices. Nevertheless, two-dimensional moire superlattices offer a powerful way to engineer diverse electronic orders in non-polar materials. Here, we report the observations of electronic ferroelectricity in monolayer graphene by introducing asymmetric moire superlattice at the graphene/h-BN interface. Utilizing Hall measurements, the electric polarization is identified to stem from electron-hole dipoles, suggesting the electronic dynamics of the observed ferroelectricity. Standard polarization-electric field hysteresis loops, as well as unconventional multiple switchable polarization states, have been achieved. By in-situ comparing with control devices, we found that the electronic ferroelectricity in graphene moire systems is independent of layer number of graphene and the corresponding fine band structures. Furthermore, we demonstrate the applications of this ferroelectric moire structures in multi-state non-volatile data storage and the emulation of versatile synaptic behaviors, including short-term plasticity, long-term potentiation and long-term depression. This work not only enriches the fundamental understanding of ferroelectricity, but also demonstrates the promising applications of graphene in multi-state memories and neuromorphic computing.
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