American Chemical Society 13, 2316−2323(2019)
Interface Engineering of Au(111) for the Growth of 1T′-MoSe2
Fang Cheng†,#, Zhixin Hu‡,#, Hai Xu†,§, Yan Shao∥, Jie Su†,§, Zhi Chen†, Wei Ji⊥, and Kian Ping Loh*,†,§
† Department of Chemistry, National University of Singapore, 117543 Singapore
‡ Center for Joint Quantum Studies and Department of Physics, Institute of Science, Tianjin University, Tianjin 300350, China
§ Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore 117546, Singapore
∥ Institute of Physics & University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100190, China
⊥ Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials
& Micro-Nano Devices, Renmin University of China, Beijing 100872, China
* Corresponding Authors: Kian Ping Loh (chmlohkp@nus.edu.sg)
Abstract
Phase-controlled synthesis of two-dimensional transition-metal dichalcogenides (TMDCs) is of great interest due to the distinct properties of the different phases. However, it is challenging to prepare metallic phase of group-VI TMDCs due to their metastability. At the monolayer level, interface engineering can be used to stabilize the metastable phase. Here, we demonstrate the selective growth of either single-layer 1H- or 1T′-MoSe2 on Au(111) by molecular-beam epitaxy; the two phases can be unambiguously distinguished using scanning tunnelling microscopy and spectroscopy. While the growth of 1H-MoSe2 is favorable on pristine Au(111), the growth of 1T′-MoSe2 is promoted by the predeposition of Se on Au(111). The selective growth of the 1T′-MoSe2 on Se-pretreated Au(111) is attributed to the Mo intercalation induced stabilization of the 1T′ phase, which is supported by density functional theory calculations. In addition, 1T′ twin boundaries and 1H–1T′ heterojunctions were observed and found to exhibit enhanced tunnelling conductivity. The substrate pretreatment approach for phase-controlled epitaxy could be applicable to other group-VI TMDCs grown on Au (111).
