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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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.
The authors declare no competing financial interests.
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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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