通过晶格严重畸变和电畴精细调控探索BiFeO3等材料的多铁和半导体性能

本项目拟通过诱导BiFeO3等多铁材料的晶格严重畸变、通过铁电畴精细结构设计，发现现有铁电相之外的新铁电相和相变，探索和优化其多铁和半导体性能。 (1) 通过外延应力或者元素掺杂显著改变BiFeO3的晶格和能带结构, 发现和研究新的铁电相或压电准同型相，研究新铁电相的(反)铁磁和磁电耦合效应；通过外力在BiFeO3薄膜中诱导非均匀应变，研究其与铁电极化的耦合关系，即挠曲电效应。 (2) 研究具有单一、有序排列铁电畴的薄膜,阐明BiFeO3新相或准同型相中的铁电畴精细结构，通过人工设计特定铁电畴精细结构优化多铁效应；研究BiFeO3的涡旋畴及畴壁电导特征，通过铁电畴精细结构调控薄膜的半导体性质，制备铁电光伏原型器件单元。　　 多铁和半导体在BiFeO3载体中既相互联系、又相对独立，通过晶格严重畸变和畴精细结构调控多铁和半导体性能，将为新型多功能电子元器件奠定材料基础。

In this project, we will find and study new ferroelectric phase and its phase transitions through introducing serious distortion of cyrstal lattice in BiFeO3 and its derivatives, and then we will imporve their multiferroic and semiconductive properties through designing fine domain structure. (1) We will introduce serious crystal lattice distortion for new ferroelectric phase, design new morphotropic phase boundaries for better piezoelectrics, and study (anti-)ferromagnetism for higher magnetoelectric coupling. Furthermore, we will study the nonlinear coupling between ferroelectric polarization and inhomogenous strain, i.e. flexoelectric effect. (2) We will design, grow and study the BiFeO3 films with uniform domain or arranged domains, clarify all kinds of fine domain structures in the new single ferroelectric phase or in mixed phases with morphotropic phase boundaries, and study the vortex domain and its abnormal conductive traits. Furthermore, we will adjust their energy band through designing special fine domain structure, improve its piezoelectric or conductive traits, and finally manipulate the resistive switching effect or improve the photovoltaic effect. In a word, we will improve the multiferroic or semiconductive effect of BiFeO3 or its derivatives, through optimizing their crystal lattice or fine domain structure. If so, this project will create a new start for new electronic devices.