Mikheev V, Chouprik A, Lebedinskii Yu, Zarubin S, Markeev A M, Zenkevich A V, Negrov D
Moscow Institute of Physics and Technology, Dolgoprudny, Russia.
Nanotechnology. 2020 Feb 10;31(21):215205. doi: 10.1088/1361-6528/ab746d.
New interest in the implementation of ferroelectric tunnel junctions has emerged following the discovery of ferroelectric properties in HfO films, which are fully compatible with silicon microelectronics technology. The coercive electric field to switch polarization direction in ferroelectric HfO is relatively high compared to classical perovskite materials, and thus it can cause the migration of non-ferroelectric charges in HfO, namely charged oxygen vacancies. The charge redistribution would cause the change of the tunnel barrier shape and following change of the electroresistance effect. In the case of ambiguous ferroelectric properties of HfO ultrathin films, this oxygen-driven resistive switching effect can mimic the tunnel electroresistance effect. Here, we demonstrate two separate resistive switching regimes, depending on the applied voltage, in the same memristor device employing a ferroelectric HfZrO (4.5 nm) layer. The first regime originates from the polarization reversal, whereas the second one is attributed to the accumulation/depletion of the oxygen vacancies at the electrode interface. The modulation of the tunnel barrier causes the enhancement of R /R ratio in ∼20 times compared to the tunnel electroresistance effect. The developed device was used to formulate the criteria for unambiguous discrimination between the ferroelectric-and non-ferroelectric resistive switching effects in HfO-based ferroelectric tunnel junctions.
在HfO薄膜中发现铁电特性后，人们对铁电隧道结的应用产生了新的兴趣，这种薄膜与硅微电子技术完全兼容。与传统的钙钛矿材料相比，铁电HfO中切换极化方向所需的矫顽电场相对较高，因此它会导致HfO中非铁电电荷的迁移，即带电氧空位的迁移。电荷重新分布会导致隧道势垒形状的改变以及随后的电阻效应变化。在HfO超薄膜铁电特性不明确的情况下，这种氧驱动的电阻切换效应可以模拟隧道电阻效应。在此，我们展示了在采用铁电HfZrO（4.5纳米）层的同一忆阻器器件中，根据施加电压存在两种不同的电阻切换机制。第一种机制源于极化反转，而第二种机制则归因于电极界面处氧空位的积累/耗尽。与隧道电阻效应相比，隧道势垒的调制使R /R 比值提高了约20倍。所开发的器件用于制定明确区分基于HfO的铁电隧道结中铁电和非铁电电阻切换效应的标准。
