Ghorai Arup, Midya Anupam, Maiti Rishi, Ray Samit K
School of Nanoscience and Technology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
Dalton Trans. 2016 Oct 14;45(38):14979-87. doi: 10.1039/c6dt02823c. Epub 2016 Aug 25.
Lithium halide assisted high yield synthesis of few layers of 2H phase semiconducting WS2 in organic solvents is reported. A group of lithium halides (LiCl, LiBr and LiI) has been employed for the first time to intercalate WS2 by using Li, followed by mild sonication to exfoliate in dispersive polar solvents. In contrast to the n-butyllithium (n-BuLi) assisted exfoliation method, which yields only the metallic 1T phase on prolonged reaction (3-7 days) at higher temperatures, the proposed exfoliation method produces only semiconducting 2H WS2 in a much shorter time (5 minute sonication). A very high yield of 19 mg ml(-1) has been obtained using LiI as an exfoliating agent due to its lower lattice energy compared to other alkali halides and the smaller size of the cation. Detailed microscopy and spectroscopic characterization reveals exfoliation of few layered WS2 with stoichiometric composition. Absorption and emission characteristics of the 2D WS2 layer exhibit a characteristic band edge and quantum confined transitions. As a proof-of-concept, we have successfully demonstrated photodetector devices comprising solution proccessed p-WS2/n-Si heterojunctions, which behave as diodes with a high rectification ratio (>10(2)) exhibiting a broad band photoresponse over the entire visible region.
据报道，在有机溶剂中，卤化锂辅助下可高产率合成几层2H相半导体WS2。首次使用一组卤化锂（LiCl、LiBr和LiI）通过锂嵌入WS2，随后在分散性极性溶剂中进行温和超声处理以剥离。与正丁基锂（n-BuLi）辅助剥离方法不同，后者在较高温度下长时间反应（3 - 7天）仅产生金属1T相，而所提出的剥离方法在更短时间（5分钟超声处理）内仅产生半导体2H WS2。由于碘化锂（LiI）与其他碱金属卤化物相比晶格能较低且阳离子尺寸较小，使用LiI作为剥离剂可获得19 mg ml(-1)的非常高的产率。详细的显微镜和光谱表征揭示了具有化学计量组成的几层WS2的剥离。二维WS2层的吸收和发射特性表现出特征带边和量子限制跃迁。作为概念验证，我们成功展示了由溶液处理的p-WS2/n-Si异质结组成的光电探测器器件，其表现为具有高整流比（>10(2)）的二极管，在整个可见光区域呈现宽带光响应。
