磁/光电协同调控HfOx薄膜的多逻辑态及其阻变机理研究

Owing to the rapid development of information age, traditional flash memory can not meet the requirements for memory. Recently, novel multifunctional resistive random access memory (RRAM) integrated with magnetoelectric or photoelectric properties has been a promising candidate for next generation memory. Focusing on the key issues for novel HfOx based memory, such as the unclear component and growth mechanism of conductive filaments, and the lack of systematic research on relationship between conductive filaments and multi logical state, this research systematically investigates the chemical stats in HfOx films under different doping systems, the electronic and the magnetic properties at different resistances, and then analyzes the microscope properties of HfOx film deeply, such as defects and filament structure. By investigating the influence of magnetic field and illumination on resistance states and the multi logic states with nonvolatile properties under the synergistic effect of electric field and magnetic field or illumination, the relationship between the variation of conductive filaments under external excitation and multi logic states is established, and microconnection between the resistive switching behaviors modulated by conductive filaments and that modulated by magnetic field or illumination is demonstrated. The filament theory is expected to illustrate the resistive switching mechanism and property of multiple logic states, and the underlying physical model will be established. The research results would play an important influence on the study of integrated circuits with properties of high density storage, low complexity and low consumption, and also provide theoretical and experimental basis for research on multiple logic state resistive memory and its mechanism.

传统的Flash存储器已不能满足目前信息时代对存储器的需求，而集光电、磁电于一体的新型阻变存储器(RRAM)有望成为下一代存储器的有力竞争者。针对新型RRAM目前存在的关键问题：导电细丝的构成和生长机理尚不明确，有关其与多逻辑态微观联系的系统研究较为缺乏，本课题以HfOx材料为研究对象，系统研究不同掺杂体系薄膜的成分、电学性能、不同阻态下的磁化曲线和电流图像，深入分析薄膜中缺陷、导电细丝构成等微观性质。重点研究磁场和光照对掺杂HfOx薄膜阻变状态的影响机理，以及磁/光电协同调控作用下薄膜的多逻辑态，建立外部激励下薄膜中导电细丝与多逻辑态的关联，明确导电细丝调节的阻变行为和磁/光调控的微观联系。预期采用导电细丝理论揭示HfOx-RRAM的阻变机理，并建立相应的物理模型。本项目的研究成果对高密度存储和低复杂度集成电路的研究具有重要意义，可为新型多功能RRAM的机理阐明和应用研究提供理论依据。

在大数据和人工智能背景下，阻变存储器(RRAM)具有结构简单、高集成度、低功耗等优点被认为是最有潜力的下一代非挥发性存储器之一。然而，阻变器件的随机性导致器件性能的波动和衰减，相关的阻变机理仍然需要深入探索。本项目提出采用多个物理量（如磁、光、电）操作器件，在开发多态存储的同时，通过多物理量下的磁电/光电效应，为阻变机理的阐明提供新的途径。因此，本项目以HfOx材料为基础，分别从掺杂HfOx薄膜的工艺优化、不同掺杂体系的缺陷特性和阻变行为、掺杂HfOx器件的磁/光电多阻态调控及阻变机理方面展开研究，并取得一定成果。通过不同掺杂体系HfOx薄膜缺陷特性、阻变性能和磁化曲线分析，表明了薄膜中的导电细丝主要由氧空位链组成。结合理论和实验分析，掺杂HfOx薄膜的铁磁性主要源于薄膜中的氧空位，同时磁性离子的掺入有助于增强薄膜的磁性。器件在不同的限流下可获得不同的低电阻状态，有无光照下可获得不同的阻态，同时通过导电细丝的形成和断裂获得的高低阻态能够表现出不同的磁饱和强度，实现了HfOx基RRAM的多级阻态存储。基于以上分析，建立了导电细丝调节的阻变行为和磁/光调控的微观联系。掺杂HfOx基RRAM的阻变过程主要源于氧空位导电细丝的形成和断裂，细丝的稳定性、氧空位浓度、磁性、带隙等可通过掺杂调控，进而可在磁电或光电协调激励下获得不同的电阻状态实现多级阻态存储器件的制备。本项目为氧化物基RRAM的应用研究提供理论依据，拓宽了RRAM的应用领域，同时，为目前信息技术快速发展下存储器小型化和智能化提供了新的途径，对下一代超高密度信息存储及多功能新型存储器的研究具有重要意义。