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Liu S, Liu Y, Holtzman L, Li B, Holbrook M, Pack J, Taniguchi T, Watanabe K, Dean CR, Pasupathy AN, Barmak K, Rhodes DA, Hone J. Two-Step Flux Synthesis of Ultrapure Transition-Metal Dichalcogenides. ACS Nano 2023; 17:16587-16596. [PMID: 37610237 DOI: 10.1021/acsnano.3c02511] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Two-dimensional transition-metal dichalcogenides (TMDs) have attracted tremendous interest due to the unusual electronic and optoelectronic properties of isolated monolayers and the ability to assemble diverse monolayers into complex heterostructures. To understand the intrinsic properties of TMDs and fully realize their potential in applications and fundamental studies, high-purity materials are required. Here, we describe the synthesis of TMD crystals using a two-step flux growth method that eliminates a major potential source of contamination. Detailed characterization of TMDs grown by this two-step method reveals charged and isovalent defects with densities an order of magnitude lower than those in TMDs grown by a single-step flux technique. For WSe2, we show that increasing the Se/W ratio during growth reduces point defect density, with crystals grown at 100:1 ratio achieving charged and isovalent defect densities below 1010 and 1011 cm-2, respectively. Initial temperature-dependent electrical transport measurements of monolayer WSe2 yield room-temperature hole mobility above 840 cm2/(V s) and low-temperature disorder-limited mobility above 44,000 cm2/(V s). Electrical transport measurements of graphene-WSe2 heterostructures fabricated from the two-step flux grown WSe2 also show superior performance: higher graphene mobility, lower charged impurity density, and well-resolved integer quantum Hall states. Finally, we demonstrate that the two-step flux technique can be used to synthesize other TMDs with similar defect densities, including semiconducting 2H-MoSe2 and 2H-MoTe2 and semimetallic Td-WTe2 and 1T'-MoTe2.
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Affiliation(s)
- Song Liu
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Yang Liu
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Luke Holtzman
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Baichang Li
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Madisen Holbrook
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - Jordan Pack
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Takashi Taniguchi
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Kenji Watanabe
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan
| | - Cory R Dean
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, New York 10027, United States
| | - Katayun Barmak
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
| | - Daniel A Rhodes
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
| | - James Hone
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States
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