Ting Cheng, the co-first author of the study. In principle, it allows us realize to grow all 2D materials into large-area single crystals if proper substrate was found." Says Dr. "This new dual-coupling epitaxy growth mechanism is new for controllable materials growth. Then all the TMD single crystals grown on a substrate with step edges are all unidirectional aligned and finally, the coalescence of these small single-crystals leads to a large single-crystal of the same size of the substrate. The coupling between WS 2 and sapphire step-edge is the second driving force and it will break the degeneracy of the two antiparallel orientations.
The WS 2-sapphireplane interaction as the first driving force, leading to two preferred antiparallel orientations of the WS 2 islands. Based on theoretical calculations, the authors proposed a mechanisms of "dual-coupling-guided epitaxy growth" for experimental design. Because TMDs has non-centrosymmetric structure or the mirror image of a TMD with respect to an edge of it has opposite alignment, we must break such a symmetry by carefully design the substrate. The key technology of epitaxially grown a large sing-crystal is to ensure that all small single-crystal grown on a substrate are uniformly aligned. Besides the WS 2, the research team also demonstrated the growth of single-crystal MoS 2, WSe 2, and MoSe 2 in wafer scale as well. Although great efforts have been dedicated to the growth of wafer-scale single-crystals of TMDs, the success was very limited until now.ĭistinguished Professor Feng Ding and his research team from the Center for Multidimensional CarbonMaterials (CMCM), within the Institute for Basic Science (IBS) at UNIST, in cooperation with researcher at Peking University (PKU), Beijing Institute of Technology, and Fudan University, reported the direct growth of 2-inch single-crystal WS 2 monolayer films very recently.
A prerequisite of building ultra-large-scale high-performance semiconducting circuits is that the base materials must be a single-crystal of wafer-scale, just like the silicon wafer used today.
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