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Transmission Electron Microscopy Observations on the Interfacial Structures of the Pt/SrBi 2 Ta 2 O 9 /Pt Thin‐Film Capacitors Prepared by Metallo‐Organic Decomposition
Author(s) -
Zhu Xinhua,
Wu Di,
Li Aidong,
Liu Zhiguo,
Ming Naiben
Publication year - 2008
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2007.02197.x
Subject(s) - high resolution transmission electron microscopy , materials science , transmission electron microscopy , capacitor , amorphous solid , annealing (glass) , electrode , thin film , platinum , analytical chemistry (journal) , nanotechnology , crystallography , composite material , chemistry , catalysis , biochemistry , chromatography , voltage , physics , quantum mechanics
Interfacial structures of the Pt/SBT/Pt capacitors prepared by metallo‐organic decomposition were examined by transmission electron microscopy (TEM) and high‐resolution TEM (HRTEM) as a function of the postannealed time at 750°C to investigate the interfacial evolution developed in the Pt/SBT/Pt capacitors. The results show that after postannealing at 750°C for a short time (e.g., 300 s), a thin amorphous layer was observed at the interfaces of the SBT/Pt‐bottom and the SBT/Pt‐top electrodes in the Pt/SBT/Pt capacitors, whereas after postannealing for a moderate time (e.g., 20 min), the interfaces of the SBT/Pt‐bottom and the SBT/Pt‐top electrodes became quite smooth and uniform, and almost free of the interfacial phase. However, after postannealing for a longer time (e.g., 60 min), an interfacial phase consisting of oval‐shaped nanocrystallites was developed at both the SBT/Pt‐bottom and the SBT/Pt‐top electrode interfaces, which resulted in weakly bonded interfaces between the SBT films and Pt electrodes. This is the reason why a Pt electrode peeling phenomenon (similar to that reported in the Pt/SBT/Pt/capacitors annealed in the forming gas atmosphere) is frequently observed in the Pt/SBT/Pt capacitors postannealed for 60 min during the fabrication of cross‐sectional TEM samples. Based on two‐dimensional lattice fringes of the HRTEM images from the small nanocrystallites and the corresponding fast Fourier transform patterns, the oval‐shaped nanocrystallites precipitated at both the SBT/Pt‐bottom and the SBT/Pt‐top electrode interfaces were determined to be a PtBi 2 phase with a cubic structure. The formation of the Pt–Bi‐based interfaces in the Pt/SBT/Pt capacitors is due to the reaction of bismuth (out‐diffused from the SBT films) with Pt electrodes during the postannealing process. The elliptical morphology of the interfacial PtBi 2 phase can be ascribed to its different growth rates in the parallel and vertical directions of the interface, and also the limited space for grain growth perpendicular to the interface.