Published October 30, 2024 | Supplemental Material
Journal Article Open

Magnetic Field‐Induced Polar Order in Monolayer Molybdenum Disulfide Transistors

  • 1. ROR icon California Institute of Technology
  • 2. ROR icon National Taiwan Normal University
  • 3. ROR icon National Chiao Tung University
  • 4. ROR icon National Cheng Kung University
  • 5. ROR icon Massachusetts Institute of Technology
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Abstract

In semiconducting monolayer transition metal dichalcogenides (ML-TMDs), broken inversion symmetry and strong spin-orbit coupling result in spin-valley lock-in effects so that the valley degeneracy may be lifted by external magnetic fields, potentially leading to real-space structural transformation. Here, magnetic field (B)-induced giant electric hysteretic responses to back-gate voltages are reported in ML-MoS2 field-effect transistors (FETs) on SiO2/Si at temperatures < 20 K. The observed hysteresis increases with |B| up to 12 T and is tunable by varying the temperature. Raman spectroscopic and scanning tunneling microscopic studies reveal significant lattice expansion with increasing |B| at 4.2 K, and this lattice expansion becomes asymmetric in ML-MoS2 FETs on rigid SiO2/Si substrates, leading to out-of-plane mirror symmetry breaking and the emergence of a tunable out-of-plane ferroelectric-like polar order. This broken symmetry-induced polarization in ML-MoS2 shows typical ferroelectric butterfly hysteresis in piezo-response force microscopy, adding ML-MoS2 to the single-layer material family that exhibits out-of-plane polar order-induced ferroelectricity, which is promising for such technological applications as cryo-temperature ultracompact non-volatile memories, memtransistors, and ultrasensitive magnetic field sensors. Moreover, the polar effect induced by asymmetric lattice expansion may be further generalized to other ML-TMDs and achieved by nanoscale strain engineering of the substrate without magnetic fields.

Copyright and License

© 2024 Wiley-VCH GmbH

Acknowledgement

The authors are grateful to Professor Patrick A. Lee for stimulating discussions on the potential physics mechanisms for the observed hysteresis, and to Yen-Yu Lai for his valuable assistance in conducting the STM experiments. The authors thank members of TLS 09A1 at the National Synchrotron Radiation Research Center's Taiwan Light Source for their suggestions on the analysis of XPS data and prior test measurements. This work was also partially supported by the Taiwan Semiconductor Research Institute for the device fabrication and the Instrumentation Center at National Tsing Hua University for the STEM experiments. National Science Foundation (US) Institue for Quantum Information and Matter at Caltech (Award #1733907), Major Research Instrument (MRI) Program (Award #DMR 2117094); National Science and Technology Council (Taiwan) MOST 111-2112-M-003-008, MOST 111-2124-M-003-005, MOST 111-2628-M-003-002-MY3, NSTC 110-2634-F-009-027, NSTC 110-2112-M-A49-013-MY3, NSTC 110-2112-M-A49-022-MY2, and NSTC 112-2926-I-003-504-G; National Taiwan Normal University Yushan Fellow Distinguished Professorship; Ministry of Education (Taiwan) Yushan Fellowship.

Contributions

D.H. and W.-H.C. contributed equally to this work. N.-C.Y., Y.-W.L., and T.-H.L. coordinated and supervised the project. W.-H.C. and T.H.Y. synthesized monolayer MoS2 single crystals, carried out device fabrication, and performed room temperature optical characterization and basic electrical measurements. D.H. carried out temperature and magnetic field-dependent electrical transport measurements, where hysteretic behavior was first discovered at a cryogenic temperature under finite magnetic fields. Y.-W.L. and N.-C.Y. conceived the idea of magnetic field-induced hysteresis response; N.-C.Y. proposed possible roles of low-temperature anisotropic lattice expansion in the occurrence of hysteresis and jointly designed further experiments with Y.-W.L. and T.-H.L. W.-H.C. carried out synchrotron XPS experiments. W.-H.C. and Y.-C.C. carried out low-temperature Raman spectroscopic studies under the supervision of T.-H.L. W.-T.L. and N.K. carried out the STM measurements under the supervision of C.-L.L. and S.-Z.H. performed the low-temperature PFM measurements under the supervision of Y.-C.C. C.-H.L. carried out the PF-KPFM measurements and estimated the carrier concentrations and sulfur vacancies. M.-H.L. assisted in analyzing experimental data from theoretical perspectives. D.H., W.-H.C., Y.-W.L., and N.-C.Y. wrote the first drafts of the paper with assistance from all other authors, and D.H. and N.-C.Y. completed the final version of the paper.

Supplemental Material

Supporting information: adma202411393-sup-0001-SuppMat.pdf

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Created:
December 18, 2024
Modified:
December 18, 2024