Mechanism of Gold-Assisted Exfoliation of Centimeter-Sized Transition-Metal Dichalcogenide Monolayers
Mechanism of Gold-Assisted Exfoliation of Centimeter-Sized Transition-Metal Dichalcogenide Monolayers
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DOI：
10.1021/acsnano.8b06101
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发表时间：
2018-10-01
期刊：
影响因子：
17.1
通讯作者：
Huang, Fumin
中科院分区：
文献类型：
--
作者：
Velicky, Matej;Donnelly, Gavin E.;Huang, Fumin
大面积单分子膜的剥离对于过渡金属二硫属化合物的基础研究和工艺实现具有重要意义。已经探索了各种技术来提高剥离产率，但对原子水平上的潜在机制知之甚少。在这里，我们展示了单层二硫化钼的金辅助机械剥离，达到厘米级。详细的光谱，显微镜，和第一性原理密度泛函理论分析表明，强大的货车德瓦尔斯（vdW）之间的相互作用Au和最顶层的二硫化钼2层有利于剥离的单分子膜。然而，这种强vdW相互作用促进的大面积剥离仅在新鲜制备的清洁且光滑的Au表面上可实现，而粗糙表面和暴露于空气中超过15分钟的表面导致可忽略的剥离产率。该技术成功地扩展到MoSe 2、WS 2、WSe 2、MoTe 2、WTe 2和GaSe。此外，电化学表征揭示了单层二硫化钼和Au之间有趣的相互作用。亚纳米厚的MoS2单层强烈钝化底层Au的化学性质，并且Au显著调制MoS2的电子能带结构，将其从半导体转变为金属。这可以在许多领域中找到应用，包括电化学、光化学和电化学。
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.