Zhang Ying, Mao Ge-Qi, Zhao Xiaolong, Li Yu, Zhang Meiyun, Wu Zuheng, Wu Wei, Sun Huajun, Guo Yizhong, Wang Lihua, Zhang Xumeng, Liu Qi, Lv Hangbing, Xue Kan-Hao, Xu Guangwei, Miao Xiangshui, Long Shibing, Liu Ming
Key Laboratory of Microelectronic Devices & Integration Technology, Institute of Microelectronics of Chinese Academy of Sciences, Beijing, 100029, China.
School of Microelectronics, University of Science and Technology of China, Hefei, 230026, China.
Nat Commun. 2021 Dec 13;12(1):7232. doi: 10.1038/s41467-021-27575-z.
The resistive switching effect in memristors typically stems from the formation and rupture of localized conductive filament paths, and HfO has been accepted as one of the most promising resistive switching materials. However, the dynamic changes in the resistive switching process, including the composition and structure of conductive filaments, and especially the evolution of conductive filament surroundings, remain controversial in HfO-based memristors. Here, the conductive filament system in the amorphous HfO-based memristors with various top electrodes is revealed to be with a quasi-core-shell structure consisting of metallic hexagonal-HfO and its crystalline surroundings (monoclinic or tetragonal HfO). The phase of the HfO shell varies with the oxygen reservation capability of the top electrode. According to extensive high-resolution transmission electron microscopy observations and ab initio calculations, the phase transition of the conductive filament shell between monoclinic and tetragonal HfO is proposed to depend on the comprehensive effects of Joule heat from the conductive filament current and the concentration of oxygen vacancies. The quasi-core-shell conductive filament system with an intrinsic barrier, which prohibits conductive filament oxidation, ensures the extreme scalability of resistive switching memristors. This study renovates the understanding of the conductive filament evolution in HfO-based memristors and provides potential inspirations to improve oxide memristors for nonvolatile storage-class memory applications.
忆阻器中的电阻开关效应通常源于局部导电丝通路的形成与断裂，而氧化铪已被公认为最具前景的电阻开关材料之一。然而，在基于氧化铪的忆阻器中，电阻开关过程中的动态变化，包括导电丝的组成与结构，尤其是导电丝周围环境的演变，仍存在争议。在此，具有各种顶部电极的非晶氧化铪基忆阻器中的导电丝系统被揭示为由金属六方氧化铪及其晶体周围环境（单斜或四方氧化铪）组成的准核壳结构。氧化铪壳的相态随顶部电极的氧保留能力而变化。根据广泛的高分辨率透射电子显微镜观察和从头算计算，提出导电丝壳在单斜氧化铪和四方氧化铪之间的相变取决于来自导电丝电流的焦耳热和氧空位浓度的综合作用。具有本征势垒（可阻止导电丝氧化）的准核壳导电丝系统确保了电阻开关忆阻器的极高可扩展性。这项研究革新了对基于氧化铪的忆阻器中导电丝演变的理解，并为改进用于非易失性存储类存储器应用的氧化物忆阻器提供了潜在的启示。
