Structural and Electrical Properties of ([SnSe]1+未)m(NbSe2)1 Compounds: Single NbSe2 Layers Separated by Increasing Thickness of SnSe

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• 作者：Matti B. Alemayehu ; Matthias Falmbigl ; Kim Ta ; Corinna Grosse ; Richard D. Westover ; Sage R. Bauers ; Saskia F. Fischer ; David C. Johnson
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：February 10, 2015
• 年：2015
• 卷：27
• 期：3
• 页码：867-875
• 全文大小：709K
• ISSN：1520-5002

文摘

The compounds ([SnSe]_1+未)_m(NbSe₂)₁, where 1 鈮?m 鈮?10, were prepared from a series of designed precursors. The c-axis lattice parameter systematically increases by 0.577(5) nm as the value of m is increased, which indicates that an additional bilayer of rock salt structured SnSe is inserted for each unit of m. The in-plane structure of both constituents systematically changes as the thickness of SnSe increases. Both X-ray diffraction and electron microscopy studies show the presence of turbostratic disorder between the different constituent layers. The electrical resistivity and Hall coefficient increase systematically as a function of m stronger than would be expected for noninteracting metallic NbSe₂ and semiconducting SnSe layers, suggesting the presence of charge transfer between the layers. The temperature dependence of the resistivity changes from metallic behavior for m < 4 to weakly increasing, for higher m, as temperature decreases. Compounds with m > 3 show an upturn in the resistivity below 50 K and a corresponding increase in the Hall coefficient, which both become more pronounced as m increases. This suggests localization of carriers, which is expected in two-dimensional crystals. The extent of charge transfer in ([SnSe]_1+未)_m(NbSe₂)₁ can be tuned as a function of SnSe thickness and spans over the same range as reported in the literature for various NbX₂ based intercalated and misfit layer compounds.