Ferroelectric tunnel junctions use a thin ferroelectric layer as a tunnelling barrier, the height of which can be modified by switching its ferroelectric polarization. The junctions can offer low power consumption, non-volatile switching and non-destructive readout, and thus are promising for the development of memory and computing applications. However, achieving a high tunnelling electroresistance (TER) in these devices remains challenging. Typical junctions, such as those based on barium titanate or hafnium dioxide, are limited by their small barrier height modulation of around 0.1 eV. Here, we report a ferroelectric tunnel junction that uses layered copper indium thiophosphate (CuInP₂S₆) as the ferroelectric barrier, and graphene and chromium as asymmetric contacts. The ferroelectric field effect in CuInP₂S₆ can induce a barrier height modulation of 1 eV in the junction, which results in a TER of above 10⁷. This modulation, which is shown using Kelvin probe force microscopy and Raman spectroscopy, is due to the low density of states and small quantum capacitance near the Dirac point of the semi-metallic graphene.

铁电隧道结使用薄的铁电层作为隧穿势垒，可以通过切换其铁电极化来更改其高度。这些结可提供低功耗，非易失性切换和无损读出的功能，因此有望用于存储器和计算应用的开发。但是，在这些器件中实现高隧穿电阻（TER）仍然具有挑战性。典型的结，例如基于钛酸钡或二氧化ha的结，受其约0.1 eV的小势垒高度调制的限制。在这里，我们报告了一个铁电隧道结，该结使用层状硫磷铜铟（CuInP ₂ S ₆）作为铁电势垒，而石墨烯和铬则作为不对称接触。CuInP ₂ S _6中的铁电场效应可在结中引起1 eV的势垒高度调制，从而导致TER大于10 ⁷。使用开尔文探针力显微镜和拉曼光谱法显示的这种调制，是由于半金属石墨烯的狄拉克点附近的状态密度低和量子电容小。