Atomically thin two-dimensional semiconductors such as MoS2 hold great promise for electrical, optical and mechanical devices and display novel physical phenomena. However, the electron mobility of mono- and few-layer MoS2 has so far been substantially below theoretically predicted limits, which has hampered efforts to observe its intrinsic quantum transport behaviours. Potential sources of disorder and scattering include defects such as sulphur vacancies in the MoS2 itself as well as extrinsic sources such as charged impurities and remote optical phonons from oxide dielectrics. To reduce extrinsic scattering, we have developed here a van der Waals heterostructure device platform where MoS2 layers are fully encapsulated within hexagonal boron nitride and electrically contacted in a multi-terminal geometry using gate-tunable graphene electrodes. Magneto-transport measurements show dramatic improvements in performance, including a record-high Hall mobility reaching 34,000 cm2 V–1 s–1 for six-layer MoS2 at low temperature, confirming that low-temperature performance in previous studies was limited by extrinsic interfacial impurities rather than bulk defects in the MoS2. We also observed Shubnikov–de Haas oscillations in high-mobility monolayer and few-layer MoS2. Modelling of potential scattering sources and quantum lifetime analysis indicate that a combination of short-range and long-range interfacial scattering limits the low-temperature mobility of MoS2.
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This research was supported by the US National Science Foundation (NSF, DMR-1122594), the NSF MRSEC programme through Columbia in the Center for Precision Assembly of Superstratic and Superatomic Solids (DMR-1420634) and in part by the FAME Center, one of six centres of STARnet, a Semiconductor Research Corporation programme sponsored by MARCO and DARPA. G-H.L. was supported by the Basic Science Research Program (NRF-2014R1A1A1004632) through the National Research Foundation (NRF) funded by the Korean government Ministry of Science, ICT and Future Planning, and in part by the Yonsei University Future-Leading Research Initiative of 2014. P.Y.H. acknowledges support from the NSF Graduate Research Fellowship Program under grant DGE-0707428. Additional support was provided through funding and shared facilities via the Cornell Center for Materials Research NSF MRSEC programme (DMR-1120296). C.-H.L. was supported by Basic Science Research Program (NRF-2014R1A1A2055112) through the National Research Foundation (NRF) funded by the Korean Government Ministry of Education, and in part by the Korea Institute of Science and Technology Institutional Program (2Z04490). F.P. and B.S.J. acknowledge support from the Center for Nanostructured Graphene (CNG), which is funded by the Danish National Research Foundation (Project DNRF58). K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by MEXT, Japan. T.T. acknowledges support from a Grant-in-Aid for Scientific Research (grant no. 262480621) and Innovative Areas ‘NanoInformatics’ (grant no. 25106006) from JSPS. The high magnetic field measurements were performed at NHMFL. The authors thank A. Suslov, B.J. Pullum, J. Billings and T. Murphy for assistance with the experiments at NHMFL.
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Nature Communications (2018)