基于氧空位发光特性的RRAM中导电细丝微观结构和阻变机制的研究

In metal oxide resistive memory (RRAM), it has become a consensus that the resistive switching mechanism is closely related to the conductive filaments formed by oxygen vacancies. However, details of the switching mechanism remain a controversial and difficult issue. The main reason for this is the lack of effective and sufficiently sensitive experimental methods to observe the resistive process at high resolution. At current stage, the research focuses on the analysis of conductive filaments using electron and X-ray spectroscopy. This process often involves exfoliating the upper electrode for probing, which places high demands on the testing technique and is destructive to the sample..In this project, the characteristics of strong emission of oxygen vacancies in oxide materials are exploited to study resistive switching. Taking the nondestructive microscopic fluorescence spectroscopy and time-resolved spectroscopy as research methods, the discrete and interconnected oxygen vacancies in conducting filaments are equivalent to zero-dimensional quantum dots and One-dimensional nanowire structure. According to their significant spectroscopic differences, the quantum structure and distribution ratio of conductive filaments under different resistance states are analyzed. By further characterizing the degree of carrier confinement and analyzing the failure mechanism of the RRAM’s endurance and retention characteristics, the intrinsic relationship between the carrier recombination and the structural configuration of conductive filament microstructure can be established. It also provides an important scientific basis for elucidating the switching mechanism of RRAM device.

在金属氧化物阻变存储器（RRAM）中，阻变机理与氧空位构成的导电细丝密切相关已成为共识。但是阻变机制的具体细节仍是一个存在争议性的难点问题，最主要的原因来源于缺乏有效和足够灵敏的实验手段对阻变过程进行高分辨率的观测。现阶段研究集中在使用电子和X射线能谱对导电细丝进行分析，往往要剥离上电极进行探测，这对测试技术和精确程度要求极高，对样品也具有破坏性。.本项目利用氧空位在氧化物材料中强发光的特性，以无损的显微荧光光谱和时间分辨光谱为研究手段，将导电细丝中分立和联通的氧空位分别等效为零维量子点和一维纳米线结构。依据它们在发光机理上存在多处显著差异，分析不同阻态下导电细丝的量子结构及其分布比例。通过进一步表征载流子束缚程度，分析RRAM器件耐久性和保持特性的失效机制，并建立载流子复合与导电细丝微观结构的内在联系，为阐释RRAM器件的工作机理提供重要的科学依据。

金属氧化物忆阻器作为非易失性存储器的代表之一，在近十年来得到了快速发展，并展现出巨大的市场前景。本项目重点围绕忆阻器中导电细丝的微观特性，通过多种微观表征手段，对忆阻器中导电细丝与器件稳定性之间的关系进行了系统研究，主要包括以下工作：（1）对忆阻器阻变机理及非理想特性进行研究，通过对不同温度及不同电阻状态下的忆阻器进行分析，得出对器件耐久性和保持特性的作用机制，并将该机制拓展到了忆阻器阵列，结合其统计分布规律对神经形态计算精度的影响进行了系统研究，并提出了基于忆阻器阵列的神经形态计算精度受温度变化影响的优化方案。（2）将完善后的导电细丝模型进行应用方面的拓展，尤其是忆阻器与传统CMOS电路相结合，对基于忆阻器的NV-SRAM与Non-Volatile Flip-Flops（NV-FF）单元进行设计与优化，实现即时休眠和零待机功耗模式。进一步研究忆阻器非理想特性对NV-SRAM与NV-FF性能的影响，通过对忆阻器与单元结构的优化以实现存储恢复能耗低、恢复率高的NV-SRAM和NV-FF。（3）把用于研究忆阻器的微观表征手段拓展到古代瓷釉中的微纳析晶、钙钛矿薄膜以及纳米线网络等结构和领域。项目组共计发表SCI收录论文13篇，其中中科院分区1区文章7篇，一篇文章为SCI、SSCI双索引。