Direct observation of 2D electrostatics and ohmic contacts in template-grown graphene/WS2 heterostructures

Changxi Zheng, Qianhui Zhang, Bent Weber, Hesameddin Ilatikhameneh, Fan Chen, Harshad Sahasrabudhe, Rajib Rahman, Shiqiang Li, Zhenchen Chen, Jack Hellerstedt, Yupeng Zhang, Wen Hui Duan, Qiaoliang Bao, Michael S. Fuhrer

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40 Citations (Scopus)

Abstract

Large-area two-dimensional (2D) heterojunctions are promising building blocks of 2D circuits. Understanding their intriguing electrostatics is pivotal but largely hindered by the lack of direct observations. Here graphene-WS2 heterojunctions are prepared over large areas using a seedless ambient-pressure chemical vapor deposition technique. Kelvin probe force microscopy, photoluminescence spectroscopy, and scanning tunneling microscopy characterize the doping in graphene-WS2 heterojunctions as-grown on sapphire and transferred to SiO2 with and without thermal annealing. Both p-n and n-n junctions are observed, and a flat-band condition (zero Schottky barrier height) is found for lightly n-doped WS2, promising low-resistance ohmic contacts. This indicates a more favorable band alignment for graphene-WS2 than has been predicted, likely explaining the low barriers observed in transport experiments on similar heterojunctions. Electrostatic modeling demonstrates that the large depletion width of the graphene-WS2 junction reflects the electrostatics of the one-dimensional junction between two-dimensional materials.

Original languageEnglish
Pages (from-to)2785-2793
Number of pages9
JournalACS Nano
Volume11
Issue number3
DOIs
Publication statusPublished - 28 Mar 2017

Keywords

  • electrostatics
  • graphene
  • heterostructure
  • ohmic contacts
  • transition-metal dichalcogenides

Cite this

Zheng, C., Zhang, Q., Weber, B., Ilatikhameneh, H., Chen, F., Sahasrabudhe, H., Rahman, R., Li, S., Chen, Z., Hellerstedt, J., Zhang, Y., Duan, W. H., Bao, Q., & Fuhrer, M. S. (2017). Direct observation of 2D electrostatics and ohmic contacts in template-grown graphene/WS2 heterostructures. ACS Nano, 11(3), 2785-2793. https://doi.org/10.1021/acsnano.6b07832