柔性透明BiFeO3等薄膜及其铁电存储器件的研究

ABO3 type perovskite ferroelectric oxides have been widely used in memories, micro-electromechanical systems and so on. However, most of the inorganic ferroelectric materials are inflexible and non-transparent, which limits the applications in flexible electronic devices and wearable transparent apparatus. This project intends to design and develop flexible and transparent perovskite oxide ferroelectric films, such as BiFeO3, and the corresponding flexible ferroelectric memory devices. The main content includes (1) High-temperature resistance and oxidation resistance flexible transparent electrode layer is deposited on the super-thin flexible and transparent substrates, such as mica. Flexible and transparent films like BiFeO3 are prepared subsequently. (2) We will study the dependence of vacancies diffusion and polarization switching on bending strains, clarify the fatigue mechanism of polarization switching under bending strains, and finally improve the anti-fatigue properties of polarization switching in these flexible oxide films. (3) We will develop the flexible and transparent ferroelectric memory devices with electrode/oxide-film/electrode sandwich structure, and these memories should have excellent bending service and bending fatigue resistance, fast speed of reading and writing, ten billion times of reading and writing, and high storage density. This project will provide a new impetus for the application of flexible and transparent oxide films like BiFeO3 in flexible electronic devices and wearable apparatus, possessing significant research and application value.

ABO3型钙钛矿铁电氧化物已经在存储器、微机电系统等方面获得了广泛的应用，传统上这些铁电材料不具有柔性和透明性，这限制了其在柔性和可穿戴透明器件中的应用。本项目拟设计和制备BiFeO3等柔性透明氧化物铁电膜和相应的铁电存储器件。具体内容包括：(1)在小于10微米厚度的柔性透明云母等基片上生长耐高温、抗氧化柔性透明电极层；制备BiFeO3等柔性透明铁电薄膜。(2)研究“弯曲应变-空位-极化翻转”之间的科学问题，阐明这些薄膜在弯曲应变下的铁电极化翻转物理机制，提高它们在弯曲状态下的极化翻转抗疲劳性质。(3)研制柔韧性好、读写信息速度快、读写次数大于一百亿次、存储密度高的柔性透明“电极/氧化物薄膜/电极”铁电存储器件，提高存储器件的弯曲服役和弯曲抗疲劳性能。本项目关于BiFeO3等柔性透明铁电薄膜及其传感器的研究对推进柔性透明电子器件的发展，具有重要的研究和应用价值。

“柔性透明BiFeO3等薄膜及其铁电存储器件的研究”项目围绕柔性钙钛矿氧化物薄膜的制备及其柔性电子器件开展研究，主要内容包括如下三个方面。第一，研究了几种具有代表性的柔性钙钛矿氧化物铁电薄膜的制备方法，分析了无机柔性钙钛矿氧化物的典型器件应用，展示了几种柔性氧化物薄膜的优异铁电、压电和介电性能。这些无机电子器件不仅具备媲美基于硬质基片薄膜器件的极佳电学性能，而且具有堪比有机可弯曲电子器件的柔韧性。第二，在云母和金箔等基片上生长钙钛矿铁电氧化物薄膜，同时通过剥离基片的方式获得柔性自支撑的钙钛矿氧化物铁电薄膜，将钙钛矿氧化物薄膜转移到预先拉伸的弹性体上，从而通过形成褶皱的方式获得柔性可拉伸氧化物薄膜。该样品能够承受4%以下的弯曲应变、30%的单向预拉伸应变及12%的等量双向预拉伸应变。第三，生长了高质量的卤素钙钛矿半导体单晶MAPbX3(X=I或Br)，发现它们具有巨大的光致伸缩效应，通过改变光强，该单晶的光致伸缩可以从几百皮米到几微米连续变化。在光强为795.5mW/cm2的532nm激光照射下，0.1-1.5mm厚的MAPbI3单晶显示出0.73-0.24%的光致伸缩。目前发表SCI论文4篇，其中柔性铁电薄膜及其应用的综述论文目前引用超过100次，申请国家发明专利1项。资助了3位博士生和3位硕士生开展研究工作。总之，本项目圆满完成了原定的研究目标。