Two-dimensional (2D) materials especially transition metal dichalcogenides (TMDs) have drawn intensive interest owing to their plentiful properties. Some TMDs with magnetic elements (Fe, Co, Ni, etc.) are reported to be magnetic theoretically and experimentally, which undoubtedly provide a promising platform to design functional devices and study physical mechanisms. Nevertheless, plenty of theoretical TMDs remain unrealized experimentally. In addition, the governable synthesis of these kinds of TMDs with desired thickness and high crystallinity poses a tricky challenge. Here, we report a controlled preparation of CoX₂ (X = S, Se, and Te) nanosheets through chemical vapor deposition. The thickness, lateral scale, and shape of the crystals show great dependence on temperature, and the thickness can be controlled from a monolayer to tens of nanometers. Magneto-transport characterization and density function theory simulation indicate that CoSe₂ and CoTe₂ are metallic. In addition, unsaturated and linear magnetoresistance have been observed even up to 9 T. The conductivity of CoSe₂ and CoTe₂ can reach 5 × 10⁶ and 1.8 × 10⁶ S/m, respectively, which is pretty high and even comparable with silver. These cobalt-based TMDs show great potential to work as 2D conductors and also provide a promising platform for investigating their magnetic properties.

中文翻译：

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具有线性磁阻和高电导率的CoX ₂（X = S，Se和Te）单晶2D层的厚度控制合成

二维（2D）材料，尤其是过渡金属二卤化物（TMD），由于其丰富的性能而引起了广泛的关注。据报道，某些带有磁性元素（Fe，Co，Ni等）的TMD在理论上和实验上都是磁性的，这无疑为设计功能器件和研究物理机理提供了有希望的平台。尽管如此，许多理论上的TMD在实验上仍未实现。另外，具有所需厚度和高结晶度的这类TMD的可控合成提出了棘手的挑战。在这里，我们报告了CoX ₂的受控制备（X = S，Se和Te）纳米片通过化学气相沉积。晶体的厚度，横向尺寸和形状对温度的依赖性很大，并且可以将厚度控制在单层至数十纳米之间。磁输运表征和密度泛函理论仿真表明，CoSe ₂和CoTe ₂是金属的。此外，不饱和的和直链磁阻已经观察甚至高达9 T. COSE的电导率₂和的CoTe ₂可达到5×10 ⁶和1.8×10 ⁶S / m分别很高，甚至可以与银相比。这些基于钴的TMD显示出作为2D导体的巨大潜力，也为研究其磁性能提供了一个有前途的平台。