扫描透射电子显微镜原位揭示ZnO纳米片缺陷的动态演变机制

Dynamic mechanism of defect evolution in ZnO nanosheets revealed by in situ scanning transmission electron microscopy

缺陷对金属氧化物的物理化学性质具有至关重要的影响,掌握缺陷的调控方法,有助于设计结构稳定、性能优异的金属氧化物材料。然而外场环境下缺陷动态结构演变原位信息的缺乏使得精确调控缺陷成为一项巨大的挑战。本文利用球差校正扫描透射电子显微镜、环境透射电子显微镜和电子层析三维重构方法原位研究了ZnO纳米片体缺陷的动态结构演变规律,探索了高温环境及氧气环境下孔洞缺陷的烧结长大与重构行为。研究发现,在外场环境下晶体缺陷以类似颗粒烧结的奥斯瓦尔德熟化和迁移长大机制烧结长大;缺陷的烧结和重构行为由降低表面能的驱动机制主导以及不同环境下氧空位浓度不同导致了不同的缺陷演变行为。

Defects play a pivotal role in dictating the physicochemical properties of metal oxides.The precise control of defects holds great promise for designing metal oxide materials with enhanced structural stability and superior performance.However,the accurate modulation of defects presents a significant challenge due to the limited availability of in situ information regarding the dynamic structural evolution of defects under external fields.Herein,using advanced techniques such as spherical aberration⁃corrected scanning transmission electron microscopy,environmental transmission electron microscopy,and electron tomography 3D reconstruction method,we investigated the dynamic structural evolution of defects in ZnO nanosheets.In situ STEM observations showed that the hole defects in ZnO nanosheets experienced sintering and reconstruction processes under high temperature vacuum/oxygen conditions.The sintering and growth of crystal defects exhibited the mechanisms of both“Oswald ripening”and“migration⁃coalescence growth”observed in nanoparticle sintering.Furthermore,the sintering and reconstruction behavior of defects are primarily governed by the reduction of surface energy and the varying concentration of oxygen vacancies in different environments,resulting in distinct patterns of defect evolution.