金属/绝缘体随机混合体系阻变效应研究

Electric-field-induced resistance switching (RS) phenomenon in oxides has attracted intense attention due to its application in nonvolatile memory. The RS mechanism can be classified into ion-based RS and electron-based RS from the point of view of physical nature. For ion-based RS, instability caused by the inevitable electroforming process, has been the bottleneck of the RS-based memory device application. In contrast to ion-based RS, electron-based RS has the potential of eliminating electroforming process ultimately and then improving RS stability since it was not correlated with long range migration of ions. The key of electron-based RS is surmounting of voltage-time dilemma. However, corresponding RS kinetics as well as conductive channel investigation is still lack so far. Size-dependent metal-insulator transition in metal/insulator random materials is a newfound electron-based RS phenomenon, which shows high stability, retention, and semiconductor technique compatibility. In this project, metal/insulator random materials will be selected as the study object, and the RS kinetics and conductive channel as well as their affecting factors will be investigated systematically concentrating on the voltage-time dilemma solution. The main objective is to expound the primitive function of electron, atom, ion, cluster, and nanophase in solving the voltage-time dilemma during RS processes, and elucidate the origin of the non-linear kinetics in metal/insulator random materials.

在基于离子机制的阻变过程中，由于电形成过程所带来的离子迁移随机性、阻变参数及器件结构的不稳定性，已经成为阻碍阻变存储器件研究的瓶颈。基于电子机制的阻变行为由于不涉及离子的长程迁移过程，具有完全消除电形成过程，提升阻变稳定性的潜力。电子阻变机制可行性的关键是"电压-时间困境"问题解决。然而在针对电子阻变机制的阻变动力学过程和导电路径的探测方面，还缺少相应的系统研究。在金属/绝缘体随机混合体系中，由尺寸效应所导致的金属-绝缘体转变是一种新发现的基于电子机制的阻变现象，具有优异的阻变稳定性、阻态保持性和工艺兼容性。本项目拟以金属/绝缘体随机混合体系为研究对象，围绕电子阻变机制的"电压-时间困境"问题，系统研究其阻变动力学过程以及导电路径的影响因素，以期揭示材料中电子、原子、离子、团簇结构以及纳米相结构等功能基元在解决"电压-时间困境"中所发挥的作用，阐明动力学过程中非线性的起源。

金属/绝缘体/金属结构中所表现的忆阻变现象是当前物理、材料领域的研究热点，可用于开发新型非易失性存储器件。本项目围绕金属/绝缘体材料的选择、电极结构设计与器件制备，研究了忆阻变过程中导电通道的形成与演变、忆阻变动力学过程的影响因素与忆阻变性能改善等方面。主要研究结果和进展体现在以下四个方面：1）阐明了银、铜等金属离子在氧化钨、氧化钼、氧化硅等绝缘介质薄膜中发挥的作用；2）提出了电极预氧化方法，获得了基于金属铜离子和氧化硅绝缘介质的性能稳定并且无电形过程的忆阻变器件；3）利用扫描近场光学显微镜技术实现了局部载流子浓度分布探测，揭示了忆阻变过程中导电通道形态的动态演变过程；4）提出了基于磁性金属/铁电绝缘介质复合磁电耦合效应的新型非易性信息存储方式和原型器件。这些研究结果为开发和设计高缩放性和稳定性的忆阻变器件奠定了理论和技术基础。