Absence of a Band Gap at the Interface of a Metal and Highly Doped Monolayer MoS2

Alexander Kerelsky, Ankur Nipane, Drew Edelberg, Dennis Wang, Xiaodong Zhou, Abdollah Motmaendadgar, Hui Gao, Saien Xie, Kibum Kang, Jiwoong Park, James Teherani, Abhay Pasupathy

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

High quality electrical contact to semiconducting transition metal dichalcogenides (TMDCs) such as MoS2 is key to unlocking their unique electronic and optoelectronic properties for fundamental research and device applications. Despite extensive experimental and theoretical efforts reliable ohmic contact to doped TMDCs remains elusive and would benefit from a better understanding of the underlying physics of the metal-TMDC interface. Here we present measurements of the atomic-scale energy band diagram of junctions between various metals and heavily doped monolayer MoS2 using ultrahigh vacuum scanning tunneling microscopy (UHV-STM). Our measurements reveal that the electronic properties of these junctions are dominated by two-dimensional metal-induced gap states (MIGS). These MIGS are characterized by a spatially growing measured gap in the local density of states (L-DOS) of the MoS2 within 2 nm of the metal-semiconductor interface. Their decay lengths extend from a minimum of ∼0.55 nm near midgap to as long as 2 nm near the band edges and are nearly identical for Au, Pd, and graphite contacts, indicating that it is a universal property of the monolayer semiconductor. Our findings indicate that even in heavily doped semiconductors, the presence of MIGS sets the ultimate limit for electrical contact.

Original languageEnglish (US)
Pages (from-to)5962-5968
Number of pages7
JournalNano Letters
Volume17
Issue number10
DOIs
StatePublished - Oct 11 2017
Externally publishedYes

All Science Journal Classification (ASJC) codes

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

Keywords

  • 2D semiconductor
  • Transition metal dichalcogenide
  • band mapping
  • molybdenum disulfide
  • ohmic contact
  • scanning tunneling microscopy/spectroscopy

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