Program of Materials Science and Engineering, Texas A&M University, College Station, TX 77843-3128, USA.
Microsc Microanal. 2013 Jun;19(3):706-15. doi: 10.1017/S1431927613000408. Epub 2013 May 1.
Heterostructures and interfacial defects in a 40-nm-thick SrTiO(3) (STO) film grown epitaxially on a single-crystal MgO (001) were investigated using aberration-corrected scanning transmission electron microscopy and geometric phase analysis. The interface of STO/MgO was found to be of the typical domain-matching epitaxy with a misfit dislocation network having a Burgers vector of ½ a(STO) <100>. Our studies also revealed that the misfit dislocation cores at the heterogeneous interface display various local cation arrangements in terms of the combination of the extra-half inserting plane and the initial film plane. The type of the inserting plane, either the SrO or the TiO(2) plane, alters with actual interfacial conditions. Contrary to previous theoretical calculations, the starting film planes were found to be dominated by the SrO layer, i.e., a SrO/MgO interface. In certain regions, the starting film planes change to the TiO(2)/MgO interface because of atomic steps at the MgO substrate surface. In particular, four basic misfit dislocation core configurations of the STO/MgO system have been identified and discussed in relation to the substrate surface terraces and possible interdiffusion. The interface structure of the system in reverse--MgO/STO--is also studied and presented for comparison.
采用相衬校正扫描透射电子显微镜和几何相位分析研究了外延生长在单晶 MgO（001）上的 40nm 厚 SrTiO3（STO）薄膜中的异质结构和界面缺陷。发现 STO/MgO 界面为典型的畴匹配外延，失配位错网络的 Burgers 矢量为 ½ a(STO) <100>。我们的研究还表明，在异质界面处的失配位错核显示出各种局部阳离子排列，这是插入半层和初始薄膜平面的组合。插入平面的类型，无论是 SrO 还是 TiO2 平面，都会随着实际的界面条件而改变。与之前的理论计算相反，发现起始薄膜平面主要由 SrO 层，即 SrO/MgO 界面主导。在某些区域，由于 MgO 衬底表面的原子台阶，起始薄膜平面会变为 TiO2/MgO 界面。特别是，已经确定并讨论了 STO/MgO 系统的四种基本失配位错核构型，与衬底表面梯级和可能的互扩散有关。还研究并呈现了该系统的逆界面结构 MgO/STO 以进行比较。
