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Phase-engineered low-resistance contacts for ultrathin MoS2 transistors

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Abstract

Ultrathin molybdenum disulphide (MoS2) has emerged as an interesting layered semiconductor because of its finite energy bandgap and the absence of dangling bonds. However, metals deposited on the semiconducting 2H phase usually form high-resistance (0.7 kΩ μm–10 kΩ μm) contacts, leading to Schottky-limited transport. In this study, we demonstrate that the metallic 1T phase of MoS2 can be locally induced on semiconducting 2H phase nanosheets, thus decreasing contact resistances to 200–300 Ω μm at zero gate bias. Field-effect transistors (FETs) with 1T phase electrodes fabricated and tested in air exhibit mobility values of ~50 cm2 V−1 s−1, subthreshold swing values below 100 mV per decade, on/off ratios of >107, drive currents approaching ~100 μA μm−1, and excellent current saturation. The deposition of different metals has limited influence on the FET performance, suggesting that the 1T/2H interface controls carrier injection into the channel. An increased reproducibility of the electrical characteristics is also obtained with our strategy based on phase engineering of MoS2.

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Figure 1: 1T and 2H phases of MoS2.
Figure 2: Contact resistance of 1T and 2H phases.
Figure 3: Properties of field-effect transistors with 1T and 2H contacts.
Figure 4: Influence of the metal electrode work function on FET properties.

Change history

  • 12 September 2014

    In the version of this Article originally published online, for Fig. 1c, the size given for the scale bar was incorrect; it should have been '5 nm'. This error has now been corrected in all versions of the Article.

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Acknowledgements

M.C., R.K. and D.V. acknowledge financial support from NSF DGE 0903661 and NSF ECCS 1128335. R.K. acknowledges support and discussions with E. Garfunkel. We acknowledge T. Fujita for the EELS data and B. Yakshinskiy for NRA. This work was done in part at the Center for Integrated Nanotechnologies, an Office of Science User Facility.

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M.C. conceived the idea, designed the experiments, analysed the data and wrote the manuscript. R.K., D.V. and A.D.M. conceived the idea and designed the experiments with M.C., synthesized the materials, fabricated the devices, made the measurements and analysed the data. S.E.Y. performed the AFM, EFM and PL mapping measurements. B.B. performed the gate dielectric depositions. G.G. helped to analyse the data and assisted in optimizing the 1T phase transformation chemistry. All the authors have read the manuscript and agree with its content.

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Correspondence to Aditya D. Mohite or Manish Chhowalla.

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Kappera, R., Voiry, D., Yalcin, S. et al. Phase-engineered low-resistance contacts for ultrathin MoS2 transistors. Nature Mater 13, 1128–1134 (2014). https://doi.org/10.1038/nmat4080

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