VI族单质薄膜结构中铁电极化行为的第一性原理研究

Nowadays, thin-film ferroelectric (FE) materials play a vital role in information industry as well as device applications. People pay more attention to compound than elemental materials due to the distinct mechanism in FE compounds. However, extending the concept of ferroelectricity to elemental systems might introduce novel polarization behaviors and offer a platform to explore the intriguing physics of two-dimensional elemental FE phases. Group VI elemental materials could favor multivalency and have no centrosymmetry, which suggests that they may be potential candidates for two-dimensional elemental FE materials. Our study has found that bilayer Te structures exhibit spontaneous in-plane polarization. Therefore, this project intends to explore the polarization mechanism in group VI elemental thin films. Firstly, we expect to clarify the different mechanisms in FE phase transition among compounds and group VI elemental thin films. The results are of significance for perfection and improvement of FE transition mechanism. Secondly, we intend to understand the interlayer coupling in multilayers and superlattice structures. Finally, we plan to explore the polarization behavior under external electric field and stress. Our research not only elucidate the FE transition mechanism in elemental thin films, but also provide new routes for the design and synthesis of two-dimentional FE materials.

铁电薄膜材料在现代信息技术中有着广阔的应用前景。近年来关于铁电薄膜的研究主要集中在化合物领域，对单质薄膜的研究相对缺乏，完善单质薄膜铁电极化内在机理有望改善薄膜材料的铁电性能。VI族单质具有多价态且在原子结构上产生了空间对称性破缺，满足构建单质铁电薄膜的条件，申请人在前期研究中发现碲元素双层厚度薄膜结构具有较强的面内自发铁电极化强度。因此，本项目基于第一性原理密度泛函理论，拟探究VI族单质薄膜的铁电极化行为：从探究单质薄膜材料铁电极化机理的问题入手，将铁电薄膜领域拓展到VI族单质材料；明确VI族单质和化合物薄膜铁电极化行为的差异性，揭示不同VI族单质薄膜铁电相变的相异机制；考察层间耦合作用对多层及超晶格结构铁电极化的影响机理；探究外场对VI族单质薄膜材料铁电极化性能的影响规律。项目研究成果将丰富和完善薄膜材料铁电极化的内在机理，并为二维铁电材料的合成设计提供新的思路和理论指导。

铁电存储器在信息技术中有着广阔的应用前景，工业上广泛应用的铁电随机存储器具有非易失性、读取速度快和高容量等优点。过往研究者对于铁电材料的研究主要集中在对复杂氧化物材料的研究上。近年来在设备微型化需求的驱动下，二维铁电材料获得了越来越多的关注。二维铁电材料的优势有以下几点：（1）原子级的厚度能够大大提高集成度，有望推动铁电器件的小型化，构建下一代电子器件；（2）可以作为拓扑绝缘体晶体管的栅极材料，通过极化翻转形成“场效应”开关，控制拓扑绝缘体的表面态电子迁移率；（3）能够构建铁电-铁磁异质结，利用界面耦合达到电控磁性甚至电致磁性的效果，更进一步应用到磁电存储器上。针对研究目标，本项目获得了科学合理的研究成果，完成了项目预期考核成果：完成了VI族薄膜材料中铁电极化的机理探究及其在铁电自旋化器件中的应用研究；探究了新型二维材料的新奇物性及其在能源领域的应用；探究了锂金属电池中分子极性对电池性能的影响。以第一作者及通讯作者发表（含录用）了SCI 收录论文5篇，其中3篇影响因子大于10（1篇为高被引论文）；与研究者合作发表了SCI论文2篇。