Defect-Tolerant Monolayer Transition Metal Dichalcogenides

Mohnish Pandey, Filip Anselm Rasmussen, Korina Kuhar, Thomas Olsen, Karsten Wedel Jacobsen, Kristian Sommer Thygesen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Localized electronic states formed inside the band gap of a semiconductor due to crystal defects can be detrimental to the material's optoelectronic properties. Semiconductors with a lower tendency to form defect induced deep gap states are termed defect-tolerant. Here we provide a systematic first-principles investigation of defect tolerance in 29 monolayer transition metal dichalcogenides (TMDs) of interest for nanoscale optoelectronics. We find that the TMDs based on group VI and X metals form deep gap states upon creation of a chalcogen (S, Se, Te) vacancy, while the TMDs based on group IV metals form only shallow defect levels and are thus predicted to be defect-tolerant. Interestingly, all the defect sensitive TMDs have valence and conduction bands with a very similar orbital composition. This indicates a bonding/antibonding nature of the gap, which in turn suggests that dangling bonds will fall inside the gap. These ideas are made quantitative by introducing a descriptor that measures the degree of similarity of the conduction and valence band manifolds. Finally, the study is generalized to nonpolar nanoribbons of the TMDs where we find that only the defect sensitive materials form edge states within the band gap.
Original languageEnglish
JournalNano letters
Volume16
Issue number4
Pages (from-to)2234-2239
Number of pages6
ISSN1530-6984
DOIs
Publication statusPublished - 2016

Keywords

  • 2D materials
  • Defect tolerance
  • Density functional theory
  • Descriptor
  • Fingerprint
  • Nanoribbon

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