高存储密度多铁隧道结的制备与物性研究

As for the trends toward device miniaturization and multi-functionalization, the conventional electronic element size is approaching quantum limits beyond which the reduction is becoming more and more difficult. One way to continue the current trends in computer power and storage increase, is to use multifunctional materials that would bring out novel physical phenomena and enable new device capabilities. A mechanism to increase the number of memory states was proposed by using a ferroelectric material as tunnel barrier in magnetic tunneling junction, making the device into a multiferroic tunnel junction (MFTJ), which exhibits four non-volatile resistance states in a single memory unit cell. In this project, we will emphatically design, fabricate and investigate the MFTJs. We will intend to explore the growth techniques of the MFTJs, concern the effects of strain, interface and domain engineering on the growth and physical properties of thin films. We will pay more attention on the spin-orbit coupling and interface-magnetoelectric effects. We will manipulate of the physical properties of the devices through electric, magnetic, and light fields, etc；and then design relevant physical effects of multi-state memory devies.

随着人们对器件小型化、多功能化的需求越来越高，传统电子器件尺寸已经接近了量子极限，因而尺寸的进一步降低变得越来越困难。在保证器件尺寸不变的情况下，一种有效的解决办法就是采用多功能材料提供新颖的物理现象和功能，从而使得计算机能力和存储密度增加等。而多铁隧道结集成了铁磁隧道结和铁电隧道结的优势，它可以在一个存储单元上实现四个非易失的电阻态，从而大大增加了信息的存储密度。本课题将研究多铁隧道结的设计、制备工艺以及物性调控；探索多铁隧道结的生长技术、工艺和机理，关注应变、界面以及畴工程等手段对多铁多层膜的结构和物性的影响；探索界面处自旋轨道耦合作用和磁电耦合效应；研究电、磁、光等多场下多铁隧道结的性能调控，并设计相应的存储原型器件。

多功能材料的磁电调控研究不仅具有重要的科学意义而且在下一代存储器领域具有很大的应用潜力，本项目在过去三年里主要研究基于铁电材料、铁磁材料异质结的磁电输运行为，以及电场、磁场、超快脉冲等对其的调控和探索强关联体系的输运行为。在npj Quantum Materials、J. Magn. Magn Mater.、Phys. Rev. Mater.、IEEE Transactions on Magnetics、Mater. Lett.等刊物发表SCI 论文12篇。具体研究成果如下：.1）.构建了基于铁电材料Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT)的多种场效应管，实现铁电极化对二维材料Bi0.94Pb0.06CuSeO (BPCSO)的磁电输运行为的调控，发现了各向异性、反弱局域化以及弱局域化共存现象；在拓扑绝缘体Cr- Bi2Se3材料的场效应管中，铁电极化实现了对其载流子浓度和类型的调控。研究了有机铁电材料P(VDF-TrFE)场效应对 (La,Sr)MnO3的氧空位浓度的调控，实现了对其电磁性质的调控。.2）.研究了Pt/Tb3Fe5O12异质结的反常Hall效应，发现在补偿点附近反常Hall电阻反号，同时矫顽力达到最大值。.3）.制备了基于无铅压电材料的铁磁/铁电异质结La0.7Sr0.3MnO3/0.5BaZr0.2Ti0.8O3-0.5Ba0.7Ca0.3TiO3 (LSMO/BZT-BCT)，系统研究了其磁电耦合效应。.4）. 制备了[LaMnO3(t)/LaAlO3(2uc)]多层膜（t=1,2,3,4）和强自旋轨道耦合体系Ca0.8La0.2IrO3外延薄膜，并系统研究了它们的磁性和输运行为；系统研究了无铅压电材料(1-x)K0.44Na0.52Li0.04Nb0.96Sb0.04O3-xBi0.25Na0.25Ba0.5ZrO3 [(1-x)KNLNS-xBNBZ] (0≤x≤0.05)的结构、介电、铁电以及压电等性质。