Structure and Electron-Transport Properties of Anion-Deficient MoTe₂: A Combined Experimental and Theoretical Study

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• 作者：Manoj K. Jana ; Anjali Singh ; Archana Sampath ; C. N. R. Rao and Umesh V. Waghmare
• 刊名：Zeitschrift für anorganische und allgemeine Chemie
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：642
• 期：23
• 页码：1386-1396
• 全文大小：2517K
• ISSN：1521-3749

文摘

We present experimental measurements and first-principles theoretical analysis of high-temperature electron-transport properties of polycrystalline Te-deficient 2H- and 1T′-MoTe_2–x. Electron transport measurements in the temperature range 300–673 K show that polycrystalline 2H-MoTe_2–x exhibits two regimes of activated conduction: hopping of defect-induced localized carriers at lower temperatures and an extended state conduction at higher temperatures. Its Seebeck coefficient changes from p-type to n-type around 497 K peaking near 370 K, which is ascribed to mixed conduction of carriers. In contrast, 1T′-MoTe_2–x exhibits metallic conduction up to 300 K beyond which conductivity slightly increases due to thermal excitation of the minority carriers. 2H- and 1T′ forms of MoTe_2–x exhibit thermal conductivity with opposite temperature-dependence due to dominant electronic thermal conductivity in the latter. Using first-principles calculations based on density functional theory, we determine the nature of defect states associated with Te-vacancies in 2H-, 1T′- and Td-MoTe_2–x. The defect bands associated with Te vacancies appear within the gap of 2H-MoTe₂ and in the pseudo gap of 1T′-MoTe₂, thereby reducing the bandgap of the former and making the latter more metallic. These defect states are crucial to understanding the observed trends in the temperature-dependent transport properties of Te-deficient 2H- and 1T′-MoTe_2–x.