Exfoliation of large-area monolayers is important for fundamental research and technological implementation of transition-metal dichalcogenides. Various techniques have been explored to increase the exfoliation yield, but little is known about the underlying mechanism at the atomic level. Here, we demonstrate gold-assisted mechanical exfoliation of monolayer molybdenum disulfide, up to a centimeter scale. Detailed spectroscopic, microscopic, and first-principles density functional theory analyses reveal that strong van der Waals (vdW) interaction between Au and the topmost MoS₂ layer facilitates the exfoliation of monolayers. However, the large-area exfoliation promoted by such strong vdW interaction is only achievable on freshly prepared clean and smooth Au surfaces, while rough surfaces and surfaces exposed to air for more than 15 min result in negligible exfoliation yields. This technique is successfully extended to MoSe₂, WS₂, WSe₂, MoTe₂, WTe₂, and GaSe. In addition, electrochemical characterization reveals intriguing interactions between monolayer MoS₂ and Au. A subnanometer-thick MoS₂ monolayer strongly passivates the chemical properties of the underlying Au, and the Au significantly modulates the electronic band structure of the MoS₂, turning it from semiconducting to metallic. This could find applications in many areas, including electrochemistry, photovoltaics, and photocatalysis.

中文翻译：

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厘米级过渡金属硫族硫化物单层金辅助剥离的机理

大面积单层剥离对过渡金属二卤化物的基础研究和技术实施很重要。已经探索了各种技术来增加剥离率，但是对于原子级的潜在机理知之甚少。在这里，我们演示了金辅助的单层二硫化钼的机械剥离，直至厘米级。详细的光谱，微观和第一性原理的密度泛函理论分析表明，Au和最高MoS ₂之间存在强范德华（vdW）相互作用层促进单层剥离。但是，只有在新鲜制备的清洁，光滑的金表面上才能实现由强力的vdW相互作用促进的大面积剥落，而粗糙的表面和暴露于空气中15分钟以上的表面导致的剥落量可忽略不计。该技术已成功扩展到MoSe ₂，WS ₂，WSe ₂，MoTe ₂，WTe ₂和GaSe。此外，电化学表征揭示了单层MoS ₂和Au之间的有趣相互作用。亚纳米厚的MoS ₂单层强烈钝化下面的Au的化学性质，Au显着调节MoS ₂的电子能带结构，将其从半导体变成金属。这可以在许多领域找到应用，包括电化学，光伏和光催化。