Defects activated photoluminescence in two-dimensional semiconductors: Interplay between bound, charged, and free excitons

Sefaattin Tongay, Joonki Suh, Can Ataca, Wen Fan, Alexander Luce, Jeong Seuk Kang, Jonathan Liu, Changhyun Ko, Rajamani Raghunathanan, Jian Zhou, Frank Ogletree, Jingbo Li, Jeffrey C. Grossman, Junqiao Wu

Research output: Contribution to journalArticlepeer-review

672 Scopus citations

Abstract

Point defects in semiconductors can trap free charge carriers and localize excitons. The interaction between these defects and charge carriers becomes stronger at reduced dimensionalities, and is expected to greatly influence physical properties of the hosting material. We investigated effects of anion vacancies in monolayer transition metal dichalcogenides as two-dimensional (2D) semiconductors where the vacancies density is controlled by α-particle irradiation or thermal-annealing. We found a new, sub-bandgap emission peak as well as increase in overall photoluminescence intensity as a result of the vacancy generation. Interestingly, these effects are absent when measured in vacuum. We conclude that in opposite to conventional wisdom, optical quality at room temperature cannot be used as criteria to assess crystal quality of the 2D semiconductors. Our results not only shed light on defect and exciton physics of 2D semiconductors, but also offer a new route toward tailoring optical properties of 2D semiconductors by defect engineering.

Original languageEnglish (US)
Article number2657
JournalScientific reports
Volume3
DOIs
StatePublished - 2013
Externally publishedYes

ASJC Scopus subject areas

  • General

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