Dual-coupling-guided epitaxial growth of wafer-scale single-crystal WS2 monolayer on vicinal a-plane sapphire
Dual-coupling-guided epitaxial growth of wafer-scale single-crystal WS2 monolayer on vicinal a-plane sapphire
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DOI：
10.1038/s41565-021-01004-0
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发表时间：
2021-11-15
影响因子：
38.3
通讯作者：
Liu, Kaihui
中科院分区：
文献类型：
--
作者：
Wang, Jinhuan;Xu, Xiaozhi;Liu, Kaihui
在绝缘衬底上生长晶片规模的单晶二维过渡金属二卤化物(TMD)对于各种高端应用至关重要(1-4)。虽然已经报道了在金属表面上外延生长晶片尺度的石墨烯和六方氮化硼(5-8)，但这些技术不适用于在绝缘衬底上生长TMD，因为生长动力学有很大的差异。因此，尽管付出了很大的努力(9-20)，但在绝缘衬底上直接生长晶片规模的单晶TMD仍未实现。本文报道了在邻近的a面蓝宝石表面上成功地外延生长两英寸单晶WS2单层膜。深入的表征和理论计算表明，外延是由双耦合机制驱动的，其中蓝宝石平面-WS2相互作用导致WS2晶体的两个择优反平行取向，而蓝宝石阶梯边-WS2相互作用破坏了反平行取向的对称性。这两个相互作用导致几乎所有WS2岛的单向排列。通过多尺度表征技术说明了WS2岛的单向排列和无缝拼接；WS2单层膜的高质量进一步证明了WS2单层膜的高质量，其光致发光圆螺旋度接近55%，与剥离的WS2片相当。我们的发现为提高绝缘体上各种二维材料的晶片规模单晶的生产提供了机会，为集成设备的应用铺平了道路。
The growth of wafer-scale single-crystal two-dimensional transition metal dichalcogenides (TMDs) on insulating substrates is critically important for a variety of high-end applications(1-4). Although the epitaxial growth of wafer-scale graphene and hexagonal boron nitride on metal surfaces has been reported(5-8), these techniques are not applicable for growing TMDs on insulating substrates because of substantial differences in growth kinetics. Thus, despite great efforts(9-20), the direct growth of wafer-scale single-crystal TMDs on insulating substrates is yet to be realized. Here we report the successful epitaxial growth of two-inch single-crystal WS2 monolayer films on vicinal a-plane sapphire surfaces. In-depth characterizations and theoretical calculations reveal that the epitaxy is driven by a dual-coupling-guided mechanism, where the sapphire plane-WS2 interaction leads to two preferred antiparallel orientations of the WS2 crystal, and sapphire step edge-WS2 interaction breaks the symmetry of the antiparallel orientations. These two interactions result in the unidirectional alignment of nearly all the WS2 islands. The unidirectional alignment and seamless stitching of WS2 islands are illustrated via multiscale characterization techniques; the high quality of WS2 monolayers is further evidenced by a photoluminescent circular helicity of similar to 55%, comparable to that of exfoliated WS2 flakes. Our findings offer the opportunity to boost the production of wafer-scale single crystals of a broad range of two-dimensional materials on insulators, paving the way to applications in integrated devices.