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Bandgap opening in MoTe2 thin flakes induced by surface oxi.

已有 344 次阅读 2020-5-6 15:28 |系统分类:科研笔记


Front. Phys. 15(3), 33602 (2020


Bandgap opening in MoTe2 thin flakes induced by surface oxidation


Yuan Gan1,2, Jiyuan Liang2, Chang-woo Cho2, Si Li3,4, Yanping Guo2, Xiaoming Ma2,5, Xuefeng Wu2, Jinsheng Wen1, Xu Du6, Mingquan He7, Chang Liu2, Shengyuan A. Yang4, Kedong Wang2, Liyuan Zhang2,*


1National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China
2Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
3School of Physics and Electronics, Hunan Normal University, Changsha 410081, China
4Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore 487372, Singapore
5Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
6Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA
7Chongqing Key Laboratory of Soft Condensed Matter Physics and Smart Materials, College of Physics, Chongqing University, Chongqing 401331, China


Recently, the layered transition metal dichalcogenide 1T′-MoTe2 has generated considerable interest due to their superconducting and non-trivial topological properties. Here, we present a systematic study on 1T′-MoTe2 single-crystal and exfoliated thin-flakes by means of electrical transport, scanning tunnelling microscope (STM) measurements and band structure calculations. For a bulk sample, it exhibits large magneto-resistance (MR) and Shubnikov–de Hass oscillations in ρxx and a series of Hall plateaus in ρxy at low temperatures. Meanwhile, the MoTe2 thin films were intensively investigated with thickness dependence. For samples, without encapsulation, an apparent transition from the intrinsic metallic to insulating state is observed by reducing thickness. In such thin films, we also observed a suppression of the MR and weak anti-localization (WAL) effects. We attributed these effects to disorders originated from the extrinsic surface chemical reaction, which is consistent with the density functional theory (DFT) calculations and in-situ STM results. In contrast to samples without encapsulated protection, we discovered an interesting superconducting transition for those samples with hexagonal Boron Nitride (h-BN) film protection. Our results indicate that the metallic or superconducting behavior is its intrinsic state, and the insulating behavior is likely caused by surface oxidation in few layer 1T′-MoTe2 flakes.



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