Jang Hyeon-Sik, Lim Jae-Young, Kang Seog-Gyun, Hyun Sang-Hwa, Sandhu Sana, Son Seok-Kyun, Lee Jae-Hyun, Whang Dongmok
School of Advanced Materials Science and Engineering and SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University (SKKU), 2066, Seobu-Ro, Jangan-Gu, Suwon-Si, Gyeonggi-Do 16419, Korea.
Department of Energy Systems Research and Department of Materials Science and Engineering, Ajou University, Suwon, Gyeonggi-Do 16499, Korea.
Nanomaterials (Basel). 2019 Nov 19;9(11):1642. doi: 10.3390/nano9111642.
The electrical and optical properties of semiconducting transition metal dichalcogenides (TMDs) can be tuned by controlling their composition and the number of layers they have. Among various TMDs, the monolayer WSe has a direct bandgap of 1.65 eV and exhibits p-type or bipolar behavior, depending on the type of contact metal. Despite these promising properties, a lack of efficient large-area production methods for high-quality, uniform WSe hinders its practical device applications. Various methods have been investigated for the synthesis of large-area monolayer WSe, but the difficulty of precisely controlling solid-state TMD precursors (WO, MoO, Se, and S powders) is a major obstacle to the synthesis of uniform TMD layers. In this work, we outline our success in growing large-area, high-quality, monolayered WSe by utilizing methane (CH) gas with precisely controlled pressure as a promoter. When compared to the catalytic growth of monolayered WSe without a gas-phase promoter, the catalytic growth of the monolayered WSe with a CH promoter reduced the nucleation density to 1/1000 and increased the grain size of monolayer WSe up to 100 μm. The significant improvement in the optical properties of the resulting WSe indicates that CH is a suitable candidate as a promoter for the synthesis of TMD materials, because it allows accurate gas control.
半导体过渡金属二硫属化物（TMDs）的电学和光学性质可以通过控制其组成和层数来调节。在各种TMDs中，单层WSe具有1.65 eV的直接带隙，并根据接触金属的类型表现出p型或双极行为。尽管具有这些有前景的特性，但缺乏用于高质量、均匀WSe的高效大面积生产方法阻碍了其在实际器件中的应用。已经研究了各种用于合成大面积单层WSe的方法，但精确控制固态TMD前驱体（WO、MoO、Se和S粉末）的难度是合成均匀TMD层的主要障碍。在这项工作中，我们概述了通过使用压力精确控制的甲烷（CH）气体作为促进剂来生长大面积、高质量单层WSe的成功经验。与没有气相促进剂的单层WSe催化生长相比，使用CH促进剂的单层WSe催化生长将成核密度降低到1/1000，并将单层WSe的晶粒尺寸增加到100μm。所得WSe光学性质的显著改善表明，CH是合成TMD材料的合适促进剂候选物，因为它允许精确的气体控制。
