Large-area growth of monolayer films of the transition metal dichalcogenides is of the utmost importance in this rapidly advancing research area. The mechanical exfoliation method offers high quality monolayer material but it is a problematic approach when applied to materials that are not air stable. One important example is 1T'-WTe2, which in multilayer form is reported to possess a large non saturating magnetoresistance, pressure induced superconductivity, and a weak antilocalization effect, but electrical data for the monolayer is yet to be reported due to its rapid degradation in air. Here we report a reliable and reproducible large-area growth process for obtaining many monolayer 1T'-WTe2 flakes. We confirmed the composition and structure of monolayer 1T'-WTe2 flakes using x-ray photoelectron spectroscopy, energy-dispersive x-ray spectroscopy, atomic force microscopy, Raman spectroscopy and aberration corrected transmission electron microscopy. We studied the time dependent degradation of monolayer 1T'-WTe2 under ambient conditions, and we used first-principles calculations to identify reaction with oxygen as the degradation mechanism. Finally we investigated the electrical properties of monolayer 1T'-WTe2 and found metallic conduction at low temperature along with a weak antilocalization effect that is evidence for strong spin-orbit coupling.

中文翻译：

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大面积合成高质量单层 1T'-WTe2 薄片。

过渡金属二硫属化物单层薄膜的大面积生长在这个快速发展的研究领域中至关重要。机械剥离方法提供了高质量的单层材料，但当应用于空气不稳定的材料时，这是一种有问题的方法。一个重要的例子是 1T'-WTe2，据报道，多层形式的 1T'-WTe2 具有较大的非饱和磁阻、压力诱导超导性和微弱的反定域效应，但由于其在空气。在这里，我们报告了一种可靠且可重复的大面积生长工艺，用于获得许多单层 1T'-WTe2 薄片。我们利用X射线光电子能谱、能量色散X射线能谱、原子力显微镜、拉曼光谱和像差校正透射电子显微镜证实了单层1T'-WTe2薄片的组成和结构。我们研究了单层 1T'-WTe2 在环境条件下的时间依赖性降解，并使用第一原理计算来确定与氧气的反应作为降解机制。最后，我们研究了单层 1T'-WTe2 的电学性质，发现低温下的金属导电性以及微弱的反局域效应，这是强自旋轨道耦合的证据。