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Yuzhou Zhao1 Xiaopeng Fan2 Jin Song1 Anlian Pan2

1, University of Wisconsin-Madison, Madison, Wisconsin, United States
2, Hunan University, Changsha, Hunan, China

Two-dimensional layered semiconductors have attracted considerable research interest, with optical and electronic properties closely related to their layer stackings. Here, we report the detailed investigation on the controllable growth and formation mechanisms of spiral WS2 nanoplates. Spiral WS2 nanoplates with controllable number of screw dislocations and defined shapes can be controllably grown by vapor phase deposition under different conditions. These structures were characterized by atomic force microscopy (AFM) and second harmonic generation (SHG) imaging, which reveal the growth mechanisms. “Spiral arm” contrast features were found at the bottom plane of the nanoplates, the number of which correlates with the number of screw dislocations initiated at the bottom plane. Different numbers of screw dislocations and orientation of layers result in the distinct morphologies and different ways of stacking, such as triangular or hexagonal spiral pattern formed on the top of the triangular spiral nanoplates. The supersaturation-dependent growth may generate new screw dislocation from the existing layers or even new layers templated by an existing screw dislocation. The discovery of these spiral WS2 nanostructures deepen our understanding and control of screw-dislocation-driven growth of two dimensional nanostructures, and offer diverse candidates for probing the physical properties of layered materials and exploring new applications in functional nanoelectronic and optoelectronic devices.

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