Antiphase Boundaries in the Turbostratically Disordered Misfit Compound (BiSe)1+未NbSe2

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• 作者：Gavin Mitchson ; Matthias Falmbigl ; Jeffrey Ditto ; David C. Johnson
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：November 2, 2015
• 年：2015
• 卷：54
• 期：21
• 页码：10309-10315
• 全文大小：352K
• ISSN：1520-510X

文摘

(BiSe)_1+未NbSe₂ ferecrystals were synthesized in order to determine whether structural modulation in BiSe layers, characterized by periodic antiphase boundaries and Bi鈥揃i bonding, occurs. Specular X-ray diffraction revealed the formation of the desired compound with a c-axis lattice parameter of 1.21 nm from precursors with a range of initial compositions and initial periodicities. In-plane X-ray diffraction scans could be indexed as hk0 reflections of the constituents, with a rectangular basal BiSe lattice and a trigonal basal NbSe₂ lattice. Electron micrographs showed extensive turbostratic disorder in the samples and the presence of periodic antiphase boundaries (approximately 1.5 nm periodicity) in BiSe layers oriented with the [110] direction parallel to the zone axis of the microscope. This indicates that the structural modulation in the BiSe layers is not due to coherency strain resulting from commensurate in-plane lattices. Electrical transport measurements indicate that holes are the dominant charge carrying species, that there is a weak decrease in resistivity as temperature decreases, and that minimal charge transfer occurs from the BiSe to NbSe₂ layers. This is consistent with the lack of charge transfer from the BiX to the TX₂ layers reported in misfit layer compounds where antiphase boundaries were observed. This suggests that electronic considerations, i.e., localization of electrons in the Bi鈥揃i pairs at the antiphase boundaries, play a dominant role in stabilizing the structural modulation.