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Electric-field induced structural transition in vertical MoTe2- and Mo1–xWxTe2-based resistive memories

Abstract

Transition metal dichalcogenides have attracted attention as potential building blocks for various electronic applications due to their atomically thin nature and polymorphism. Here, we report an electric-field-induced structural transition from a 2H semiconducting to a distorted transient structure (2Hd) and orthorhombic Td conducting phase in vertical 2H-MoTe2- and Mo1−xWxTe2-based resistive random access memory (RRAM) devices. RRAM programming voltages are tunable by the transition metal dichalcogenide thickness and show a distinctive trend of requiring lower electric fields for Mo1−xWxTe2 alloys versus MoTe2 compounds. Devices showed reproducible resistive switching within 10 ns between a high resistive state and a low resistive state. Moreover, using an Al2O3/MoTe2 stack, On/off current ratios of 106 with programming currents lower than 1 μA were achieved in a selectorless RRAM architecture. The sum of these findings demonstrates that controlled electrical state switching in two-dimensional materials is achievable and highlights the potential of transition metal dichalcogenides for memory applications.

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Fig. 1: Vertical TMD-based device characterization.
Fig. 2: 2H-MoTe2- and 2H-Mo1−xWxTe2-based RRAM behaviour and their set voltages as a function of flake thickness.
Fig. 3: C-AFM and STEM measurements and analysis.
Fig. 4: STEM images and resistance of vertical MoTe2-based devices versus temperature in their respective 2H phase, HRS, LRS and 1T′ phase.
Fig. 5: Performance of 2H-MoTe2-based RRAM under pulsed operation.
Fig. 6: Performance of 2H-Al2O3/MoTe2-based RRAM.

Data availability

The data that support the plots within this paper are available from the corresponding author upon request.

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Acknowledgements

This work was supported in part by the Semiconductor Research Corporation (SRC) at the NEWLIMITS Center and National Institute of Standards and Technology (NIST) through award no. 70NANB17H041. S.K. acknowledges support from the US Department of Commerce, NIST under financial assistance award 70NANB16H043. H.Z. acknowledges support from the US Department of Commerce, NIST under financial assistance awards 70NANB15H025 and 70NANB17H249. A.V.D., S.K. and B.P.B. acknowledge support from Material Genome Initiative funding allocated to NIST. The authors thank I. Kalish (NIST) for conducting XRD and EDS measurements on Mo1–xWxTe2 samples. Certain commercial equipment, instruments or materials are identified in this paper to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by NIST, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose.

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Contributions

F.Z. and J.A. designed the experiments. F.Z. fabricated, measured the devices and performed the conductive AFM measurement. S.K. and A.V.D. synthesized Mo1–xWxTe2 alloy samples. C.A.M. and D.Y.Z. performed the STM and STS measurements. D.Y.Z. contributed the STM surface analysis. H.Z. prepared TEM samples using SEM/FIB and performed TEM/STEM measurements. H.Z., L.A.B. and A.V.D. performed the TEM/STEM analysis. B.P.B. conducted ab initio modelling of energetics for the 2H, 2Hd and 1T′ MoTe2. Y.Z. and J.A. carried out the model simulation for vertical electrical transport. F.Z., H.Z., L.A.B., A.V.D. and J.A. wrote the manuscript and discussed the results at all stages.

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Correspondence to Huairuo Zhang or Joerg Appenzeller.

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Sections 1–14, Supplementary References 1–14, Supplementary Table 1, Supplementary Figures 1–17

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Zhang, F., Zhang, H., Krylyuk, S. et al. Electric-field induced structural transition in vertical MoTe2- and Mo1–xWxTe2-based resistive memories. Nature Mater 18, 55–61 (2019). https://doi.org/10.1038/s41563-018-0234-y

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