铁电薄膜中180°荷电畴壁的亚埃尺度结构特性

Sub-angstrom structural characteristics of zig-zag 180°charged domain walls in ferroelectric films

本文利用透射电子显微术研究了铁电PbTiO_3薄膜中形成的锯齿状头对头180°荷电畴壁。衬度分析表明薄膜中存在高密度的180°畴。像差校正电镜研究发现180°畴壁处晶格转角呈现顺时针和逆时针交替排布,其极化呈头对头分布,且在180°畴壁处面外晶格受到压缩而面内晶格参数保持不变,进而导致了畴壁处四方度的减小,认为这种畴壁的形成是由表面或界面电荷分布不均匀导致反向c畴在该处形核长大造成。

Diffraction contrast analysis and aberration-corrected scanning transmission electron microscopy were applied to study the zigzag head-to-head 180° domain wall in PbTiO_3 films grown on SrTiO_3. It is found that the lattice rotation is alternately clockwise and counterclockwise distributing along the zigzag 180° domain wall. The out-of-plane lattice parameter is contracted, while the in-plane lattice parameter keeps constant, resulting in a reduced tetragonality. The formation of such kind of domain wall may be attributed to the inhomogeneous distribution of electric charges at interface and surface, where the c-domain can nucleate and grow.