Université Grenoble Alpes, F-38000, Grenoble, France.
CEA, LETI, Minatec Campus, F-38054, Grenoble, France.
Adv Mater. 2017 Jun;29(23). doi: 10.1002/adma.201700212. Epub 2017 Apr 18.
The control and rational design of redox-based memristive devices, which are highly attractive candidates for next-generation nonvolatile memory and logic applications, is complicated by competing and poorly understood switching mechanisms, which can result in two coexisting resistance hystereses that have opposite voltage polarity. These competing processes can be defined as regular and anomalous resistive switching. Despite significant characterization efforts, the complex nanoscale redox processes that drive anomalous resistive switching and their implications for current transport remain poorly understood. Here, lateral and vertical mapping of O vacancy concentrations is used during the operation of such devices in situ in an aberration corrected transmission electron microscope to explain the anomalous switching mechanism. It is found that an increase (decrease) in the overall O vacancy concentration within the device after positive (negative) biasing of the Schottky-type electrode is associated with the electrocatalytic release and reincorporation of oxygen at the electrode/oxide interface and is responsible for the resistance change. This fundamental insight presents a novel perspective on resistive switching processes and opens up new technological opportunities for the implementation of memristive devices, as anomalous switching can now be suppressed selectively or used deliberately to achieve the desirable so-called deep Reset.
基于氧化还原的忆阻器件的控制和合理设计对于下一代非易失性存储器和逻辑应用极具吸引力，然而其复杂的开关机制（竞争且理解不充分）导致了两种共存的具有相反电压极性的电阻滞后现象。这些竞争过程可以定义为常规和异常电阻开关。尽管已经进行了大量的特性分析，但对于驱动异常电阻开关的复杂纳米级氧化还原过程及其对电流传输的影响仍知之甚少。在这里，在配备了像差校正装置的透射电子显微镜中对这种器件进行原位操作，利用横向和纵向的 O 空位浓度映射来解释异常开关机制。研究发现，肖特基型电极正（负）偏压后器件内总 O 空位浓度的增加（减少）与电极/氧化物界面处的氧的电催化释放和再掺入有关，这是导致电阻变化的原因。这一基本见解为电阻开关过程提供了新的视角，并为忆阻器件的实现开辟了新的技术机遇，因为现在可以有选择地抑制异常开关，或者故意利用异常开关来实现所谓的深复位。
