自组织纳米复合薄膜BiFeO3-CoFe2O4的微结构与相成分

采用先进电子显微术在原子尺度研究了(001)单晶SrTiO₃衬底上生长的纳米复合薄膜0.65BiFcO₃-0.35CoFe₂O₄的组织形态以及界面结构.BiFeO₃(BFO)和CoFe₂O₄(CFO)两相在外延生长过程中自发相分离,形成自组织的复合纳米结构.磁性尖晶石CFO呈方块状均匀分布于铁电钙钛矿BFO基体中,并沿[001)1]方向外延生长,形成垂直的柱状纳米结构.两相具有简单的立方-立方取向关系,即[001]_BFO//[001]_CFO和(100)_BFO//(100)_CFO,且界面为{110}晶面.薄膜表面起伏不平,形成CFO{111}小刻面而BFO则为平整的(001)表面.能谱分析结果表明各相成分均匀分布并无明显的元素互扩散发生.

Microstructure and phase constituents of self-assembled BiFeO3-CoFe2O4 nano-composite thin films

The morphologies and interface structure of self-assembled 0.65BiFeO₃-O.35COFe₂O₄ nanocomposite thin films on (001)-SrTiO₃ single crystal substrates were studied by advanced transmission electron microscopy (TEM) techniques at the atomic scale. During the process of thin-film epitaxial growth, BiFeO₃ (BFO) and CoFe₂0₄ (CFO) separate spontaneously and form a self-assembled composite nanostructure. The ferromagnetic spinel CFO forms nanopillars presenting a rectangular shape embedded in the ferroelectric perovskite BFO matrix, and both grow epitaxially along the[001] orientation and then get a vertical columnar nanostructure. The two phases give a cube-on-cube orientation relationship,[001]BFO//[001]CFO and (100)BFO//(100)CFO, and the interface between them lies in the {110} orientation. The surface of the composite film is rough with {111} facets of CFO and a smooth surface of BFO resides on the (001) plane. Energy-dispersive spectroscopy (EDS) studies show that the constituents of each phase present homogeneous distribution and no obvious interdiffusion is observed across the interface.