铁电场效应调制Mott金属-绝缘体转变及相关原型器件的制备与性能研究

Most recently, Mott transistors have triggered considerable interests because of their uniquely electronic switching behaviors that originate from the electrostatically-doping-induced metal-insulator transition (MIT). This makes the Mott transistors a promising candidate to overcome the scaling limitation of conventional Si-based semiconductor memory devices. In this project, we propose a novel Mott transistor scheme utilizing ferroelectric materials as the gate oxides and ultrathin perovskite nickelates RNiO3 (R is a lanthanide cation excepting the lanthanum) as the channels, inspired by the ferroelectric field effect transistors. In these ferroelectric/RNiO3 heterostructures the density of carriers in the Mott channels are modulated by the ferroelectric field effect associated with the reversal of spontaneous polarization in the ferroelectric gating, which gives rise to the metal-insulator transition, as a result of the modification of charge ordering, and hence to the electronic switching behaviors of non-volatile data storage fashion. The MIT temperatures of the ultrathin RNiO3 channels of interest in the present proposal are adjusted to near room temperature through artificial microstructure modulation. Pulsed laser deposition is employed to grow high quality ferroelectric/RNiO3 heterostructures with atomically smoothing interfaces. The origins of the non-volatile Mott switching characteristics are explored in terms of the ferroelectric field effect. The effects of microstructure parameters on the in-plane electrical transport of the ferroelectric/RNiO3 heterostructures and on the reliability of the prototypal Mott transistors are evaluated carefully. These will provide substantial basis for application of the proposed ferroelectric Mott transistors in non-volatile memories with the advantages of high write/read speed and high data storage density and also contribute to the development of nanoelectronic devices based on correlated oxide systems.

Mott场效应管所特有的静电掺杂导致金属-绝缘体转变的电开关机制使其成为有潜力突破当前Si基半导体技术物理极限的重要备选方案，而备受业界关注。本项目拟借鉴铁电场效应管的工作原理，以铁电体作为栅极氧化物，超薄钙钛矿镍酸盐RNiO3（R为除La之外的镧系元素）作为沟道，提出基于铁电体/RNiO3的Mott场效应结构。利用自发极化双稳态和铁电场效应来调制沟道载流子浓度，改变RNiO3电荷序并诱导金属-绝缘体转变，从而获得非挥发电开关特性。本项目将通过人工微结构调控获得可在室温工作的RNiO3超薄膜，采用脉冲激光沉积制备具有原子级平整界面的高质量铁电体/RNiO3外延异质结构，探索若干微结构参数对该结构面内输运行为的影响，澄清铁电场效应作用机制，考察原型器件的数据存储可靠性，为Mott场效应结构在高速、高密度非挥发信息存储上的应用打下基础，并为强关联材料纳米电子学器件的发展提供支持。

项目执行期间，围绕ReNiO3型稀土镍酸盐薄膜异质结构和铁电场效应调控，开展了如下研究工作。首先，探索了LaAlO3、NdGaO3、SrTiO3等多种商业化基片的湿化学处理工艺，获得了单原子层结尾的台阶形貌表面，为高质量外延生长提供了平台。系统探索了脉冲激光沉积的工艺参数，优化了LaNiO3、NdNiO3、SmNiO3等多种稀土镍酸盐薄膜的表面／界面形貌、外延关系、金属-绝缘体转变行为等，获得了“生长工艺-微结构-电输运特性”之间的作用规律。基于此，我们制备了介电体／ReNiO3、铁电体／ReNiO3等多种异质结构，探索了介电响应，铁电极化等对ReNiO3超薄膜输运特性的影响。进一步的，基于耐高温、可弯曲的Mica基片，利用SrTiO3作为种子层，LaAlO3作为应变调控缓冲层，通过控制LaAlO3层的厚度和晶格弛豫程度，约束在其上生长的稀土镍酸盐（以NdNiO3为例）的晶格结构和面内／面外应变，从而调控了NdNiO3/LaAlO3/SrTiO3/Mica异质结构的输运特性和金属-绝缘体转变温度，其电阻率变化达到了2个量级，并且在高达1000次的反复凹／凸弯曲下性能稳定可重复。这些实验结果为柔性信息器件的设计和制备提供了新的解决方案。另外，我们提出了铁电场效应调控界面Schottky势垒的铁电隧穿阻变存储器件，通过极化翻转调控了界面输运行为，同时改变了Schottky势垒的高度和宽度，获得了巨大的ON/OFF开关比值和优良的阻变特性。并且，我们还探索了基于金属性LaNiO3电极的铁电隧道结的势垒厚度效应，制备了用于Crossbar存储阵列的互补铁电开关等，这些工作为新型信息存储器件，特别是基于电输运开关特性的场效应器件的发展打下了理论和材料体系的研究基础。. 项目资助发表SCI论文8篇，其中以项目主持人为通讯作者，在《Nature Communications》、《Advanced Materials》、《Applied Physics Letters》、《ACS Applied Materials & Interfaces》等期刊发表7篇，1篇论文入选了ESI高被引用。授权发明专利1项。完成了本课题的研究任务。

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