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Flexible metallic nanowires with self-adaptive contacts to semiconducting transition-metal dichalcogenide monolayers

Abstract

In the pursuit of ultrasmall electronic components1,2,3,4,5, monolayer electronic devices have recently been fabricated using transition-metal dichalcogenides6,7,8. Monolayers of these materials are semiconducting, but nanowires with stoichiometry MX (M = Mo or W, X = S or Se) have been predicted to be metallic9,10. Such nanowires have been chemically synthesized11,12,13. However, the controlled connection of individual nanowires to monolayers, an important step in creating a two-dimensional integrated circuit, has so far remained elusive. In this work, by steering a focused electron beam, we directly fabricate MX nanowires that are less than a nanometre in width and Y junctions that connect designated points within a transition-metal dichalcogenide monolayer. In situ electrical measurements demonstrate that these nanowires are metallic, so they may serve as interconnects in future flexible nanocircuits fabricated entirely from the same monolayer. Sequential atom-resolved Z-contrast images reveal that the nanowires rotate and flex continuously under momentum transfer from the electron beam, while maintaining their structural integrity. They therefore exhibit self-adaptive connections to the monolayer from which they are sculpted. We find that the nanowires remain conductive while undergoing severe mechanical deformations, thus showing promise for mechanically robust flexible electronics. Density functional theory calculations further confirm the metallicity of the nanowires and account for their beam-induced mechanical behaviour. These results show that direct patterning of one-dimensional conducting nanowires in two-dimensional semiconducting materials with nanometre precision is possible using electron-beam-based techniques.

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Figure 1: Fabrication of nanowires from TMDC monolayers using a focused electron beam.
Figure 2: In situ electrical measurement of a MoSe nanowire.
Figure 3: Atomic structure of the nanowire.
Figure 4: Flexing and discrete rotations of a nanowire between junctions.

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Acknowledgements

The authors thank H. Conley for helping with the transfer of the samples, E. Rowe, E. Tupitsyn and P. Bhattacharya for early technical assistance on the samples, and R. Ishikawa, R. Mishra, B. Wang and J. Lou for discussions. This research was supported in part by the US Department of Energy (DOE; grant DE-FG02-09ER46554 to J.L. and S.T.P.), a Wigner Fellowship through the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC, for the US DOE (W.Z.), the Office of Basic Energy Sciences, Materials Sciences and Engineering Division, US DOE (A.R.L., N.J.G., J.Q.Y., D.G.M., S.J.P. and S.T.P.) and through a user project supported by ORNL's Center for Nanophase Materials Sciences (CNMS), which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US DOE (J.C.I.). K.I.B. and D.P. were supported by ONR N000141310299. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the US DOE (contract no. DE-AC02-05CH11231). O.C. and K.S. acknowledge the Japan Science and Technology Agency (JST) research acceleration programme for financial support. N.T.C., M.O. and S.O. acknowledge support from the JST-CREST programme.

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J.L. and O.C. designed and carried out the experiments and analysed the data. J.L. performed the STEM experiments and first-principles calculations. O.C. performed in situ transport measurements. D.P. and K.I.B. participated in sample preparation. D.C. and A.B. provided the bulk MoSe2 sample. N.J.G., J.Y. and D.G.M. provided the bulk MoSe2 and WSe2 samples. N.T.C., M.O. and S.O. contributed to DFT calculations. W.Z., J.C.I. and A.R.L. participated in STEM experiments. W.Z., K.S., S.J.P. and S.T.P. supervised the project. J.L., O.C. and W.Z. wrote the manuscript, with advice from K.S., S.J.P. and S.T.P. This work was performed in partial fulfilment of the requirements for a PhD degree by J.L.

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Correspondence to Junhao Lin or Wu Zhou.

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The authors declare no competing financial interests.

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Lin, J., Cretu, O., Zhou, W. et al. Flexible metallic nanowires with self-adaptive contacts to semiconducting transition-metal dichalcogenide monolayers. Nature Nanotech 9, 436–442 (2014). https://doi.org/10.1038/nnano.2014.81

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