The high tunneling electroresistance (TER) effect, generally caused by ferroelectric (FE)-modulated barrier height or width, is essential for the applications of multiferroic tunnel junctions in data storage. It is traditionally obtained by distinct electrical screening lengths of electrodes. Interface engineering can enhance the TER effect further. In this work, taking $\mathrm{Co}\text{−}{\left({\mathrm{TiO}}_2\text{−}\mathrm{BaO}\right)}_N\text{−}\mathrm{Co}$ tunnel junctions as examples, we demonstrate a distinct principle than the screening lengths for designing extraordinary TER effect. We reveal that when the interfacial FE displacement is much larger than that of the FE bulk, it will bend the barrier band near the interface violently, and the interfacial polarization direction pointing to or away from the interface determines whether the energy band rises or falls. The large interfacial Ba-O displacement and its corresponding polarization direction in $\mathrm{Co}\text{−}{\mathrm{BaTiO}}_3\text{−}\mathrm{Co}$ tunnel junctions can be significantly modulated by the direction of FE polarization, resulting in a metallic-insulating transition of the entire thin ${\mathrm{BaTiO}}_3$ barrier. For thick ${\mathrm{BaTiO}}_3$ barrier ($N=25$, $\sim 10$ nm), the effective tunnel barrier width shifts between about 2 nm and 6.5 nm as the polarization of ${\mathrm{BaTiO}}_3$ switches direction, which can dramatically modulate the tunneling efficiency. This effect shed light on a novel route for enhancing TER through the interface engineering.

中文翻译：

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多铁性隧道结中势垒高度和宽度的巨大铁电调制

通常由铁电 (FE) 调制势垒高度或宽度引起的高隧道电阻 (TER) 效应对于多铁性隧道结在数据存储中的应用至关重要。它传统上是通过电极的不同电屏蔽长度来获得的。界面工程可以进一步增强TER效应。在这项工作中，采取$\mathrm{公司}\text{-}{\left({\mathrm{二氧化钛}}_2\text{-}\mathrm{氧化钡}\right)}_N\text{-}\mathrm{公司}$以隧道结为例，我们展示了一个不同于屏蔽长度的独特原理，用于设计非凡的 TER 效应。我们发现当界面有限元位移远大于有限元体的位移时，它将剧烈弯曲界面附近的势垒带，指向或远离界面的界面极化方向决定了能带是上升还是下降。大的界面 Ba-O 位移及其对应的极化方向$\mathrm{公司}\text{-}{\mathrm{钛酸钡}}_3\text{-}\mathrm{公司}$ 隧道结可以通过 FE 极化方向显着调制，导致整个薄层的金属绝缘过渡 ${\mathrm{钛酸钡}}_3$障碍。对于厚${\mathrm{钛酸钡}}_3$ 障碍 （$N=25$, $～10$ nm)，有效隧道势垒宽度在大约 2 nm 和 6.5 nm 之间移动，因为 ${\mathrm{钛酸钡}}_3$切换方向，这可以显着调节隧道效率。这种效应揭示了通过界面工程增强 TER 的新途径。