Step-Edge-Guided Nucleation and Growth of Aligned WSe2 on Sapphire via a Layer-over-Layer Growth Mode

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• 作者：Liang Chen ; Bilu Liu ; Mingyuan Ge ; Yuqiang Ma ; Ahmad N. Abbas ; Chongwu Zhou
• 刊名：ACS Nano
• 出版年：2015
• 出版时间：August 25, 2015
• 年：2015
• 卷：9
• 期：8
• 页码：8368-8375
• 全文大小：559K
• ISSN：1936-086X

文摘

Two-dimensional (2D) materials beyond graphene have drawn a lot of attention recently. Among the large family of 2D materials, transitional metal dichalcogenides (TMDCs), for example, molybdenum disulfides (MoS₂) and tungsten diselenides (WSe₂), have been demonstrated to be good candidates for advanced electronics, optoelectronics, and other applications. Growth of large single-crystalline domains and continuous films of monolayer TMDCs has been achieved recently. Usually, these TMDC flakes nucleate randomly on substrates, and their orientation cannot be controlled. Nucleation control and orientation control are important steps in 2D material growth, because randomly nucleated and orientated flakes will form grain boundaries when adjacent flakes merge together, and the formation of grain boundaries may degrade mechanical and electrical properties of as-grown materials. The use of single crystalline substrates enables the alignment of as-grown TMDC flakes via a substrate鈥揻lake epitaxial interaction, as demonstrated recently. Here we report a step-edge-guided nucleation and growth approach for the aligned growth of 2D WSe₂ by a chemical vapor deposition method using C-plane sapphire as substrates. We found that at temperatures above 950 掳C the growth is strongly guided by the atomic steps on the sapphire surface, which leads to the aligned growth of WSe₂ along the step edges on the sapphire substrate. In addition, such atomic steps facilitate a layer-over-layer overlapping process to form few-layer WSe₂ structures, which is different from the classical layer-by-layer mode for thin-film growth. This work introduces an efficient way to achieve oriented growth of 2D WSe₂ and adds fresh knowledge on the growth mechanism of WSe₂ and potentially other 2D materials.