Ferroelectric tunnel junctions have recently attracted a lot of research interest, not only for memory operation but also for e.g. neuromorphic computing. Retention characteristics of these devices are of utmost importance in many applications. The authors have recently demonstrated the feasibility of double-layered ferroelectric tunnel junctions where the ferroelectric hafnium zirconium oxide acts as the memory layer and the dielectric aluminium oxide as the tunnelling barrier. The depolarisation field from the unscreened polarisation charges that is introduced by this structure causes serious limitations on the retention behaviour due to the unintentional back-switching of ferroelectric domains. This leads to a diminishing memory window over time. By using a built-in bias field from different work function metal electrodes, in this case platinum and titanium nitride with 0.85 eV difference, one can shift the polarisation hysteresis curve and counteract the electric depolarisation field. This leads to a more stable on-current over time while only marginally increasing the off-current degradation. Extrapolation to ten years shows a much larger memory window compared to the symmetric metal electrode structure.

中文翻译：

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内置偏置场，用于基于氧化f的铁电隧道结中的保持稳定性

铁电隧道结最近吸引了许多研究兴趣，不仅用于存储器操作，而且还用于例如神经形态计算。这些设备的保持特性在许多应用中至关重要。作者最近证明了双层铁电隧道结的可行性，其中铁电ha锆氧化物充当存储层，介电氧化铝作为隧道势垒。由于铁电畴的无意反向切换，由此结构引入的来自未屏蔽极化电荷的去极化场对保留行为造成了严重限制。随着时间的推移，这将导致内存窗口的减少。通过使用来自不同功函数金属电极的内置偏置场，在这种情况下，铂和氮化钛的差值为0.85 eV，可以移动极化磁滞曲线并抵消去极化电场。这导致随时间变化的导通电流更加稳定，而仅略微增加了截止电流的下降。与对称金属电极结构相比，外推至十年显示出更大的存储窗口。