Van der Waals Bonded Co/h-BN Contacts to Ultrathin Black Phosphorus Devices

Ahmet Avsar, Jun Y. Tan, Xin Luo, Khoong Hong Khoo, Yuting Yeo, Kenji Watanabe, Takashi Taniguchi, Su Ying Quek, Barbaros Özyilmaz

Research output: Journal article publicationJournal articleAcademic researchpeer-review

45 Citations (Scopus)


Because of the chemical inertness of two dimensional (2D) hexagonal-boron nitride (h-BN), few atomic-layer h-BN is often used to encapsulate air-sensitive 2D crystals such as black phosphorus (BP). However, the effects of h-BN on Schottky barrier height, doping, and contact resistance are not well-known. Here, we investigate these effects by fabricating h-BN encapsulated BP transistors with cobalt (Co) contacts. In sharp contrast to directly Co contacted p-type BP devices, we observe strong n-type conduction upon insertion of the h-BN at the Co/BP interface. First-principles calculations show that this difference arises from the much larger interface dipole at the Co/h-BN interface compared to the Co/BP interface, which reduces the work function of the Co/h-BN contact. The Co/h-BN contacts exhibit low contact resistances (∼4.5 kω) and are Schottky barrier-free. This allows us to probe high electron mobilities (4,200 cm2/(V s)) and observe insulator-metal transitions even under two-terminal measurement geometry.
Original languageEnglish
Pages (from-to)5361-5367
Number of pages7
JournalNano Letters
Issue number9
Publication statusPublished - 13 Sept 2017


  • black phosphorus
  • boron nitride
  • encapsulation
  • tunnel barrier
  • Work-function

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering


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