金属氧化物中点缺陷行为的像差校正电镜研究

Studies of point defects in metal oxides by aberration-corrected transmission electron microscopy

金属氧化物在自然界中无处不在,在科学前沿和技术应用方面都吸引了人们的广泛关注。然而,相对于金属和半导体,人们对金属氧化物中表面、界面、位错和点缺陷的认识仍然处于初级阶段。除了氧化物的结构本身比较复杂以外,缺乏合适的结构分析手段也是一个重要原因。像差校正透射电子显微术不仅提供了更高的空间分辨率,而且基本消除了图像衬度中的离域效应,越来越成为晶格缺陷的原子尺度结构分析的重要工具。本文以尖晶石氧化物的表面重构和多铁性稀土铁氧化物的有序结构为例,介绍了作者近期应用像差校正电镜对材料中点缺陷的原子构型的研究。在尖晶石的表面重构中,确定了次表面阳离子间隙的新的排布,并得到了迄今为止能量最低的表面结构,发现了表面化学键过饱和的现象;在多铁性稀土氧化物的有序结构中,确定了氧间隙离子排布的空间调制矢量,得到了具有相同空间调制矢量的阳离子电荷有序。

Metal oxides are ubiquitous in nature,and have attracted extensive attention in fundamental science and technology applications.Compared with metals and semiconductors,however,the understanding of surfaces,interfaces,dislocations and point defects in metal oxides is still in its infancy.In addition to the complex crystal structure of oxides,lacking proper analysis methods is also one of the main reason for the status.Aberration-corrected transmission electron microscopy not only provides higher spatial resolution,but also eliminates the delocalization effect in image contrast.It has become an important tool for atomic-scale structure analysis of lattice defects.Taking the surface reconstruction of spinel oxides and the ordered structure of multiferroic rare earth iron oxides as examples,the recent studies on the atomic configuration of point defects in materials by aberration correction electron microscopy are introduced.In the study of surface reconstruction of spinel oxides,subsurface redistribution of cation interstitials was determined and the lowest surface energy to date as well as the over-saturation of surface bonds were found.In the study of the ordered structure of multiferroic rare earth iron oxides,the space modulation vector of the distribution of the oxygen interstitials was determined and the charge order of cations with the same space modulation vector was revealed.