铁电薄膜中倾斜带电畴壁的导电性调控及其多值存储研究

The multilevel storage (MLS) has attracted great interest in non-volatile memory due to its ultra-high data storage density. In this project, it is proposed that the titled charged domain wall (CDW) in ferroelectric can be used as the storage unit for the MLS. Theoretically, the model based on the phase field method combined with semiconductor theory will be developed to investigate the characteristics of the titled CDW. Another model will be established to analyze the conductivities of the CDW with different titling angle. Experimentally, the titled CDW will be realized in the lead zirconate titanate (PZT) epitaxial semiconductor ferroelectric films and its microstructures, stabilities, tilting properties and conductivities will be investigated by in-situ transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) along with conductive atomic force microscopy (C-AFM). Then, combined with the experimental and theoretical studies, the relationship between carrier type, carrier concentration, the microstructure and property of titled CDW will be studied. The corresponding conduction mechanism and large-range modulation technology will be revealed essentially. Finally, ferroelectric MLS based on CDW can be achieved by controlling the microstructure and conductivity of tilted CDW. This project will shed the light for the next-generation MLS in ferroelectric.

可在单个存储单元内存储多个逻辑态的多值存储技术，因其可实现超高密度存储，成为了非挥发存储领域研究的热点。本申请项目提出使用倾斜带电的铁电畴壁作为功能单元来实现多值存储。一方面，结合相场理论和半导体理论，建立铁电半导体薄膜中倾斜带电畴壁的相场分析模型和畴壁倾斜角度与导电性关联模型；另一方面，结合利用原位透射电子显微镜、压电力响应显微镜和导电探针显微镜，在锆钛酸铅外延铁电半导体薄膜中制备倾斜带电畴壁并观测和分析其微观结构、稳定性、倾斜可调性和导电性；最后，结合实验和理论分析载流子类型和浓度、畴壁微观结构与畴壁特性的关联，研究倾斜带电畴壁导电的微观本质和调控机理，探讨其导电性宽区间调控的实现方法，进而控制倾斜带电畴壁的倾转性、微观结构获得宽的导电调控区间实现基于倾斜带电畴壁的铁电多值存储。为新一代超高密度铁电多值存储器的开发提供指导和依据。

本项目紧紧围绕倾斜带电铁电畴壁的导电性进行了一系列研究。首先，利用脉冲激光沉积方法开展和实现了具有不同类型铁电畴壁结构的PZT(Pb(ZrxTi1-x)O3(x = 0, 0.1, 0.8, 0.52)外延薄膜的可控生长。其次，基于PZT外延铁电薄膜，利用原位透射电子显微镜(in-situ TEM)和压电力显微镜(PFM)定向诱导了各种类型的铁电或铁弹畴壁，再结合原位TEM、PFM和导电原子力显微镜(c-AFM)测试手段分析了其微观结构、稳定性、导电性及其与畴壁倾斜性的关联。理论上，结合相场理论和半导体理论建立了PZT铁电薄膜中倾斜带电畴壁的微观结构和导电性理论关联模型，探讨了不同条件下倾斜畴壁的导电性。通过实验和理论系统研究了倾斜带电畴壁微结构和导电性的关联、倾斜带电畴壁导电性的调控机理，并初步应用到多值存储纳米器件中。这些研究结果可以为倾斜带电铁电畴壁的导电性及调控机理的理解和新一代超高密度铁电多值存储的开发提供一定的指导和依据。