Li Changjian, Song Dongsheng, Li Mengsha, Tang Chunhua, Xue Deqing, Wan Dongyang, Pennycook Stephen J
Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore.
Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore; NUSNNI-Nanocore, National University of Singapore, 117411 Singapore.
Ultramicroscopy. 2019 Aug;203:82-87. doi: 10.1016/j.ultramic.2019.03.003. Epub 2019 Mar 4.
Niobium-based oxides have a wide range of applications owing to their rich crystal and electronic structures. Defects at the atomic scale are always unavoidable and will affect their functionalities, especially when in the form of thin films. Here, atomic resolution scanning transmission electron microscopy and electron energy loss spectroscopy have been performed on various defects (point, line, planar defects and segregated phases) in alkaline and alkaline-earth niobate thin films: CaZrO modified (K, Na)NbO and strontium niobate (SNO), respectively. In CaZrO modified (K,Na)NbO thin films, a tetragonal tungsten bronze phase was found, with a sharp boundary with the perovskite phase. In SNO thin films, several kinds of point defects and antiphase boundaries are commonly observed. In addition, a strongly Sr deficient phase, SrNbO, precipitates inside the SrNbO phase with a coherent interface. The different oxidation states of Nb in SrNbO and SrNbO were revealed from the O K edge. Our characterization of the point defects and extended defects in niobate thin films offers practical guidelines for thin film deposition or discovery of defect-based novel functionalities.
铌基氧化物因其丰富的晶体结构和电子结构而具有广泛的应用。原子尺度的缺陷总是不可避免的，并且会影响它们的功能，特别是当它们以薄膜形式存在时。在这里，我们利用原子分辨率扫描透射电子显微镜和电子能量损失谱对碱金属和碱土金属铌酸盐薄膜（分别为CaZrO改性的(K,Na)NbO和铌酸锶(SNO)）中的各种缺陷（点缺陷、线缺陷、面缺陷和偏析相）进行了研究。在CaZrO改性的(K,Na)NbO薄膜中，发现了一种四方钨青铜相，它与钙钛矿相之间有明显的边界。在SNO薄膜中，通常观察到几种点缺陷和反相畴界。此外，一种严重缺Sr的相SrNbO，以共格界面在SrNbO相内部析出。从O K边揭示了SrNbO和SrNbO中Nb的不同氧化态。我们对铌酸盐薄膜中点缺陷和扩展缺陷的表征为薄膜沉积或基于缺陷的新型功能的发现提供了实用指南。
