TiO2／BiFeO3薄膜中增强的磁性和铁电性能

摘要

In order to improve the ferroelectric property of BiFeO3( BFO) film, TiO2/BiFeO3 composite films and BiFeO3 ( BFO ) films on Au/Pt/Cr/Si substrates were prepared by a sol⁃gel process and magnetron sputtering. The films were characterized by using scanning probe microscope ( SPM ) , scanning electron microscope ( SEM ) , X⁃ray diffraction ( XRD ) , ferroelectric instrument and physical properties of the measuring instrument ( PPMS) . The results show that TiO2 layers suppress the formation of surface defect , improve the insulation of the BFO films, and thus significantly reduced lower leakage current density. The main conduction mechanism shows a transformation from ohmic conduction to space charge limited conduction as increasing electric field. Moreover, sputtering TiO2 layer on the surface of BFO films destroyed the spiral structure of BFO films. The interface stress between TiO2 and BFO induced by lattice mismatch improves magnetoelectric properties. The barrier layer between the ferroelectric film and the top electrode is an effective approach to improve the performance of ferroelectric materials.%为改善铁酸铋（ BiFeO3）薄膜的铁电性能，通过溶胶－凝胶和磁控溅射的方法在 Au／Pt／Cr／Si 基底上制备了TiO2／BiFeO3（ TiO2／BFO）和BiFeO3薄膜。采用扫描探针显微镜、扫描电子显微镜、X射线衍射仪、铁电测试仪和物理性能测量仪对薄膜进行了物性表征。实验结果表明：TiO2阻挡层抑制了BFO薄膜表面缺陷的形成，提高了复合薄膜的绝缘性能，使TiO2／BFO薄膜中泄漏电流明显降低，且导电机制由欧姆型向空间电荷限制传导型转变。此外，溅射TiO2阻挡层破坏了BFO表面的螺旋结构，使TiO2和BFO之间晶格失配而产生界面应力，提高了薄膜的磁电性能。在顶电极和铁电层之间引入阻挡层是提高BFO薄膜磁电性能的一种有效方法。