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Controlling phase transition in WSe2 towards ideal n-type transistor

Abstract

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have been rapidly established as promising building blocks for versatile atomic scale circuits and multifunctional devices. However, the high contact resistance in TMDs based transistors seriously hinders their applications in complementary electronics. In this work, we show that an Ohmic homojunction n-type tungsten diselenide (WSe2) transistor is realized through spatially controlling cesium (Cs) doping region near the contacts. We find that the remarkable electron doping effect of Cs stimulates a semiconductor to metal (2H to 1T’) phase transition in WSe2, and hence the formation of 2H-1T’ hetero-phase contact. Our method significantly optimizes the WSe2 transport behavior with a perfect low subthreshold swing of ∼ 61 mV/dec and ultrahigh current on/off ratio exceeding ∼ 109. Meanwhile, the electron mobility is enhanced by nearly 50 times. We elucidate that the ideal n-type behavior originates from the negligible Schottky barrier height of ∼ 19 meV and low contact resistance of ∼ 0.9 kΩ·µm in the 2H-1T’ homojunction device. Moreover, based on the Ohmic hetero-phase configuration, a WSe2 inverter is achieved with a high gain of ∼ 270 and low power consumption of ∼ 28 pW. Our findings envision Cs functionalization as an effective method to realize ideal Ohmic contact in 2D WSe2 transistors towards high performance complementary electronic devices.

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Acknowledgements

Authors acknowledge the financial support from the National Natural Science Foundation of China (Nos. U2032147, 21872100 and 62004128), Singapore MOE Grants MOE-2019-T2-1-002, the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDB30000000) and Fundamental Research Foundation of Shenzhen (Nos. JCYJ20170817100405375 and JCYJ20190808152607389).

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Correspondence to Du Xiang or Wei Chen.

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Zheng, Y., Xiang, D., Zhang, J. et al. Controlling phase transition in WSe2 towards ideal n-type transistor. Nano Res. 14, 2703–2710 (2021). https://doi.org/10.1007/s12274-020-3275-x

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  • DOI: https://doi.org/10.1007/s12274-020-3275-x

Keywords

  • WSe2
  • Cs intercalation
  • semiconductor to metal phase transition
  • ideal hetero-phase transistor
  • high gain homo-inverter