Li Meng, Curnan Matthew T, Gresh-Sill Michael A, House Stephen D, Saidi Wissam A, Yang Judith C
Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA, USA.
Department of Mechanical Engineering & Materials Science,, University of Pittsburgh, Pittsburgh, PA, USA.
Nat Commun. 2021 May 13;12(1):2781. doi: 10.1038/s41467-021-23043-w.
Elucidating metal oxide growth mechanisms is essential for precisely designing and fabricating nanostructured oxides with broad applications in energy and electronics. However, current epitaxial oxide growth methods are based on macroscopic empirical knowledge, lacking fundamental guidance at the nanoscale. Using correlated in situ environmental transmission electron microscopy, statistically-validated quantitative analysis, and density functional theory calculations, we show epitaxial CuO nano-island growth on Cu is layer-by-layer along CuO(110) planes, regardless of substrate orientation, contradicting classical models that predict multi-layer growth parallel to substrate surfaces. Growth kinetics show cubic relationships with time, indicating individual oxide monolayers follow Frank-van der Merwe growth whereas oxide islands follow Stranski-Krastanov growth. Cu sources for island growth transition from step edges to bulk substrates during oxidation, contrasting with classical corrosion theories which assume subsurface sources predominate. Our results resolve alternative epitaxial island growth mechanisms, improving the understanding of oxidation dynamics critical for advanced manufacturing at the nanoscale.
阐明金属氧化物生长机制对于精确设计和制造在能源与电子领域具有广泛应用的纳米结构氧化物至关重要。然而，当前的外延氧化物生长方法基于宏观经验知识，在纳米尺度上缺乏基本指导。通过结合原位环境透射电子显微镜、经过统计验证的定量分析以及密度泛函理论计算，我们发现CuO纳米岛在Cu上沿着CuO(110)平面逐层外延生长，与衬底取向无关，这与预测平行于衬底表面多层生长的经典模型相矛盾。生长动力学与时间呈立方关系，表明单个氧化物单层遵循弗兰克 - 范德梅韦生长，而氧化物岛遵循斯特兰斯基 - 克拉斯坦诺夫生长。在氧化过程中，岛生长的铜源从台阶边缘转变为块状衬底，这与假设次表面源占主导的经典腐蚀理论形成对比。我们的结果解决了外延岛生长的替代机制，增进了对纳米尺度先进制造至关重要的氧化动力学的理解。
