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Phase-engineered low-resistance contacts for ultrathin MoS2 transistors

Nature Materials volume 13, pages 1128–1134 (2014)Cite this article

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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.

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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.

References

  1. Radisavljevic, B., Radenovic, A., Brivio, J., Giacometti, V. & Kis, A. Single-layer MoS2 transistors. Nature Nanotech. 6, 147–150 (2011).

    CAS  Google Scholar 

  2. Wang, Q. H., Kalantar-Zadeh, K., Kis, A., Coleman, J. N. & Strano, M. S. Electronics and optoelectronics of two-dimensional transition metal dichalcogenides. Nature Nanotech. 7, 699–712 (2012).

    CAS  Google Scholar 

  3. Jariwala, D., Sangwan, V. K., Lauhon, L. J., Marks, T. J. & Hersam, M. C. Emerging device applications for semiconducting two-dimensional transition metal dichalcogenides. ACS Nano 8, 1102–1120 (2014).

    Article  CAS  Google Scholar 

  4. Zhu, W. et al. Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition. Nature Commun. 5, 3087 (2014).

    Google Scholar 

  5. Das, S. & Appenzeller, J. Where does the current flow in two-dimensional layered systems? Nano Lett. 13, 3396–3402 (2013).

    CAS  Google Scholar 

  6. Chang, H-Y., Zhu, W. & Akinwande, D. On the mobility and contact resistance evaluation for transistors based on MoS2 or two-dimensional semiconducting atomic crystals. Appl. Phys. Lett. 104, 113504 (2014).

    Google Scholar 

  7. Liu, H., Neal, A. T. & Ye, P. D. Channel length scaling of MoS2 MOSFETs. ACS Nano 6, 8563–8569 (2012).

    CAS  Google Scholar 

  8. Liu, H. et al. Switching mechanism in single-layer molybdenum disulfide transistors: An insight into current flow across Schottky barriers. ACS Nano 8, 1031–1038 (2014).

    CAS  Google Scholar 

  9. Liu, W. et al. High-performance few-layer-MoS2 field-effect-transistor with record low contact-resistance Electron Devices Meet. IEDM 2013 IEEE Int. 19.4.1–19.4.4 (2013)

  10. McDonnell, S., Addou, R., Buie, C., Wallace, R. M. & Hinkle, C. L. Defect-dominated doping and contact resistance in MoS2 . ACS Nano 8, 2880–2888 (2014).

    CAS  Google Scholar 

  11. Radisavljevic, B., Whitwick, M. B. & Kis, A. Integrated circuits and logic operations based on single-layer MoS2 . ACS Nano 5, 9934–9938 (2011).

    CAS  Google Scholar 

  12. Wang, H. et al. Integrated circuits based on bilayer MoS2 transistors. Nano Lett. 12, 4674–4680 (2012).

    CAS  Google Scholar 

  13. Lee, H. S. et al. MoS2 nanosheet phototransistors with thickness-modulated optical energy gap. Nano Lett. 12, 3695–3700 (2012).

    CAS  Google Scholar 

  14. Yoon, Y., Ganapathi, K. & Salahuddin, S. How good can monolayer MoS2 transistors be? Nano Lett. 11, 3768–3773 (2011).

    CAS  Google Scholar 

  15. Jena, D. & Konar, A. Enhancement of carrier mobility in semiconductor nanostructures by dielectric engineering. Phys. Rev. Lett. 98, 136805 (2007).

    Google Scholar 

  16. Walia, S. et al. Characterization of metal contacts for two-dimensional MoS2 nanoflakes. Appl. Phys. Lett. 103, 232105 (2013).

    Google Scholar 

  17. Das, S., Chen, H-Y., Penumatcha, A. V. & Appenzeller, J. High performance multilayer MoS2 transistors with scandium contacts. Nano Lett. 13, 100–105 (2013).

    CAS  Google Scholar 

  18. Chen, J-R. et al. Control of Schottky barriers in single layer MoS2 transistors with ferromagnetic contacts. Nano Lett. 13, 3106–3110 (2013).

    CAS  Google Scholar 

  19. Dankert, A., Langouche, L., Kamalakar, M. V. & Dash, S. P. High-performance molybdenum disulfide field-effect transistors with spin tunnel contacts. ACS Nano 8, 476–482 (2014).

    CAS  Google Scholar 

  20. Chuang, S. et al. MoS2 p-type transistors and diodes enabled by high work function MoOx contacts. Nano Lett. 14, 1337–1342 (2014).

    CAS  Google Scholar 

  21. Radisavljevic, B. & Kis, A. Mobility engineering and a metal–insulator transition in monolayer MoS2 . Nature Mater. 12, 815–820 (2013).

    CAS  Google Scholar 

  22. Bao, W., Cai, X., Kim, D., Sridhara, K. & Fuhrer, M. S. High mobility ambipolar MoS2 field-effect transistors: Substrate and dielectric effects. Appl. Phys. Lett. 102, 042104 (2013).

    Google Scholar 

  23. Jariwala, D. et al. Band-like transport in high mobility unencapsulated single-layer MoS2 transistors. Appl. Phys. Lett. 102, 173107 (2013).

    Google Scholar 

  24. Lin, J. et al. Flexible metallic nanowires with self-adaptive contacts to semiconducting transition-metal dichalcogenide monolayers. Nature Nanotech. 9, 436–442 (2014).

    CAS  Google Scholar 

  25. Kim, S. et al. High-mobility and low-power thin-film transistors based on multilayer MoS2 crystals. Nature Commun. 3, 1011 (2012).

    Google Scholar 

  26. Liu, H. & Ye, P. D. MoS2 dual-gate MOSFET with atomic-layer-deposited Al2O3 as top-gate dielectric. IEEE Electron Device Lett. 33, 546–548 (2012).

    CAS  Google Scholar 

  27. Baugher, B. W. H., Churchill, H. O. H., Yang, Y. & Jarillo-Herrero, P. Intrinsic electronic transport properties of high-quality monolayer and bilayer MoS2 . Nano Lett. 13, 4212–4216 (2013).

    CAS  Google Scholar 

  28. Schmidt, H. et al. Transport properties of monolayer MoS2 grown by chemical vapor deposition. Nano Lett. 14, 1909–1913 (2014).

    CAS  Google Scholar 

  29. Sangwan, V. K. et al. Low-frequency electronic noise in single-layer MoS2 transistors. Nano Lett. 13, 4351–4355 (2013).

    CAS  Google Scholar 

  30. Qiu, H. et al. Electrical characterization of back-gated bi-layer MoS2 field-effect transistors and the effect of ambient on their performances. Appl. Phys. Lett. 100, 123104 (2012).

    Google Scholar 

  31. Park, W. et al. Oxygen environmental and passivation effects on molybdenum disulfide field effect transistors. Nanotechnology 24, 095202 (2013).

    Google Scholar 

  32. Zhang, W. et al. High-gain phototransistors based on a CVD MoS2 monolayer. Adv. Mater. 25, 3456–3461 (2013).

    CAS  Google Scholar 

  33. Kang, J., Liu, W. & Banerjee, K. High-performance MoS2 transistors with low-resistance molybdenum contacts. Appl. Phys. Lett. 104, 093106 (2014).

    Google Scholar 

  34. Popov, I., Seifert, G. & Tománek, D. Designing electrical contacts to MoS2 monolayers: A computational study. Phys. Rev. Lett. 108, 156802 (2012).

    Google Scholar 

  35. Buscema, M. et al. Large and tunable photothermoelectric effect in single-layer MoS2 . Nano Lett. 13, 358–363 (2013).

    CAS  Google Scholar 

  36. Ghatak, S., Pal, A. N. & Ghosh, A. Nature of electronic states in atomically thin MoS2 field-effect transistors. ACS Nano 5, 7707–7712 (2011).

    CAS  Google Scholar 

  37. Fang, H. et al. Degenerate n-doping of few-layer transition metal dichalcogenides by potassium. Nano Lett. 13, 1991–1995 (2013).

    CAS  Google Scholar 

  38. Eda, G. et al. Photoluminescence from chemically exfoliated MoS2 . Nano Lett. 11, 5111–5116 (2011).

    CAS  Google Scholar 

  39. Voiry, D. et al. Enhanced catalytic activity in strained chemically exfoliated WS2 nanosheets for hydrogen evolution. Nature Mater. 12, 850–855 (2013).

    CAS  Google Scholar 

  40. Dines, M. B. Lithium intercalation via n-butyl lithium of the layered transition metal dichalcogenides. Mater. Res. Bull. 10, 287–291 (1975).

    CAS  Google Scholar 

  41. Joensen, P., Frindt, R. F. & Morrison, S. R. Single-layer MoS2 . Mater. Res. Bull. 21, 457–461 (1986).

    CAS  Google Scholar 

  42. Py, M. A. & Haering, R. R. Structural destabilization induced by lithium intercalation in MoS2 and related compounds. Can. J. Phys. 61, 76–84 (1983).

    CAS  Google Scholar 

  43. Mulhern, P. J. Lithium intercalation in crystalline LixMoS2 . Can. J. Phys. 67, 1049–1052 (1989).

    CAS  Google Scholar 

  44. Kertesz, M. & Hoffmann, R. Octahedral versus trigonal-prismatic coordination and clustering in transition-metal dichalcogenides. J. Am. Chem. Soc. 106, 3453–3460 (1984).

    CAS  Google Scholar 

  45. Enyashin, A. N. & Seifert, G. Density-functional study of LixMoS2 intercalates (0 ≤ x ≤ 1). Comput. Theor. Chem. 999, 13–20 (2012).

    CAS  Google Scholar 

  46. Chhowalla, M. et al. The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets. Nature Chem. 5, 263–275 (2013).

    Google Scholar 

  47. Joensen, P., Crozier, E. D., Alberding, N. & Frindt, R. F. A study of single-layer and restacked MoS2 by X-ray diffraction and X-ray absorption spectroscopy. J. Phys. C 20, 4043–4053 (1987).

    CAS  Google Scholar 

  48. Jiménez Sandoval, S., Yang, D., Frindt, R. & Irwin, J. Raman study and lattice dynamics of single molecular layers of MoS2 . Phys. Rev. B 44, 3955–3962 (1991).

    Google Scholar 

  49. Yang, D., Sandoval, S. J., Divigalpitiya, W. M. R., Irwin, J. C. & Frindt, R. F. Structure of single-molecular-layer MoS2 . Phys. Rev. B 43, 12053–12056 (1991).

    CAS  Google Scholar 

  50. Heising, J. & Kanatzidis, M. G. Structure of restacked MoS2 and WS2 elucidated by electron crystallography. J. Am. Chem. Soc. 121, 638–643 (1999).

    CAS  Google Scholar 

  51. Wypych, F. & Schollhorn, R. 1T-MoS2, a new metallic modification of molybdenum disulfide. J. Chem. Soc. Chem. Commun. 19, 1386–1388 (1992).

    Google Scholar 

  52. Tsai, H-L., Heising, J., Schindler, J. L., Kannewurf, C. R. & Kanatzidis, M. G. Exfoliated–restacked phase of WS2 . Chem. Mater. 9, 879–882 (1997).

    CAS  Google Scholar 

  53. Eda, G. et al. Coherent atomic and electronic heterostructures of single-layer MoS2 . ACS Nano 6, 7311–7317 (2012).

    CAS  Google Scholar 

  54. Fuhrer, M. S. & Hone, J. Measurement of mobility in dual-gated MoS2 transistors. Nature Nanotech. 8, 146–147 (2013).

    CAS  Google Scholar 

  55. International Technology Roadmap for Semiconductorswww.itrs.net (ITRS, 2012)

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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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Authors and Affiliations

  1. Materials Science and Engineering, Rutgers University, 607 Taylor Road, Piscataway, New Jersey 08854, USA

    Rajesh Kappera, Damien Voiry & Manish Chhowalla

  2. MPA-11 Materials Synthesis and Integrated Devices, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

    Sibel Ebru Yalcin, Brittany Branch, Gautam Gupta & Aditya D. Mohite

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Contributions

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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