Screw-Dislocation-Driven Growth of Two-Dimensional Few-Layer and Pyramid-like WSe2 by Sulfur-Assisted Chemical Vapor Deposition

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• 作者：Liang Chen ; Bilu Liu ; Ahmad N. Abbas ; Yuqiang Ma ; Xin Fang ; Yihang Liu ; Chongwu Zhou
• 刊名：ACS Nano
• 出版年：2014
• 出版时间：November 25, 2014
• 年：2014
• 卷：8
• 期：11
• 页码：11543-11551
• 全文大小：617K
• ISSN：1936-086X

文摘

Two-dimensional (2D) layered tungsten diselenides (WSe₂) material has recently drawn a lot of attention due to its unique optoelectronic properties and ambipolar transport behavior. However, direct chemical vapor deposition (CVD) synthesis of 2D WSe₂ is not as straightforward as other 2D materials due to the low reactivity between reactants in WSe₂ synthesis. In addition, the growth mechanism of WSe₂ in such CVD process remains unclear. Here we report the observation of a screw-dislocation-driven (SDD) spiral growth of 2D WSe₂ flakes and pyramid-like structures using a sulfur-assisted CVD method. Few-layer and pyramid-like WSe₂ flakes instead of monolayer were synthesized by introducing a small amount of sulfur as a reducer to help the selenization of WO₃, which is the precursor of tungsten. Clear observations of steps, helical fringes, and herringbone contours under atomic force microscope characterization reveal the existence of screw dislocations in the as-grown WSe₂. The generation and propagation mechanisms of screw dislocations during the growth of WSe₂ were discussed. Back-gated field-effect transistors were made on these 2D WSe₂ materials, which show on/off current ratios of 10⁶ and mobility up to 44 cm²/(V路s).

Keywords:

tungsten diselenides; WSe₂; screw dislocation; two-dimensional layered materials; transition metal dichalcogenides; TMDC; chemical vapor deposition