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.

中文翻译：

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表面氧化在MoTe 2薄片中的带隙开口

近来，由于层状过渡金属二硫化二氢1T'-MoTe ₂具有超导和非平凡的拓扑特性，引起了人们的极大兴趣。在这里，我们通过电传输，扫描隧道显微镜（STM）测量和能带结构计算，对1T'-MoTe ₂单晶和剥落的薄片进行系统的研究。对于大块样品，它表现出大的磁阻（MR）和舒勃尼科夫-德哈斯振荡ρ XX和一系列霍尔高原在ρ的XY在低温下。同时，MoTe ₂对薄膜的厚度依赖性进行了深入研究。对于没有封装的样品，通过减小厚度可以观察到从本征金属态到绝缘态的明显过渡。在这种薄膜中，我们还观察到了MR抑制和弱的抗局部定位（WAL）效应。我们将这些影响归因于外在表面化学反应引起的疾病，这与密度泛函理论（DFT）计算和原位STM结果一致。与没有封装保护的样品相反，我们发现了具有六方氮化硼（h-BN）薄膜保护。我们的结果表明，金属或超导行为是其固有状态，而绝缘行为很可能是由少数1T'-MoTe ₂薄片的表面氧化引起的。