Spectroscopic correlation of chalcogen defects in atomically thin MoS2(1−x)Se2x alloys

Research output: Contribution to journalArticlepeer-review


  • Rahul Sharma
  • Juhi Pandey
  • Krishna Rani Sahoo
  • Kewal Singh Rana
  • Ajay Soni
  • Tharangattu N. Narayanan

Colleges, School and Institutes

External organisations

  • Tata Institute of Fundamental Research
  • Indian Institute of Technology
  • Nanoscale Physics Research Laboratory


Engineering of atomically thin transition metal dichalcogenides (TMDs) is highly sought after for novel optoelectronic and spintronic devices. With the limited number of naturally existing TMDs, chalcogen based alloying has become a viable solution for developing TMDs for optical modulators and photovoltaics. Here, we report on detailed optical and microscopic studies of ternary TMD alloys of molybdenum, sulfur, and selenium grown via a single step method. The developed material has tunable band gaps in a broad range 1.5–1.9 eV with the variation in sulfur compositions. Further, the existence of trions, bi-excitons, and defect bound excitons are shown using temperature dependent (4 K−300 K) photoluminescence spectroscopy. A detailed analysis on MoS1.34Se0.66 alloy system shows the evidence of new types of defect bound excitons originating at low temperatures along with the presence of bi-excitons having a binding energy of ∼41 meV. The prospects of defect induced quasiparticles are observed in scanning transmission electron microscope assisted analyses and verified using density functional theory calculations. The thermal conductivity values, calculated using micro-Raman studies, of MoS2, MoSe2, and MoS1.34Se0.66 are found to be 69(±2) W m1 K1, 33(±2) W m1 K1 and 17(±2) W m1 K1 respectively, in agreement with the theoretical predictions. Tunable optical properties of these ternary atomic layers along with moderate thermal conductivity reveal the potential of these layers in modern opto-electronic devices and sensors.

Bibliographic note

Funding Information: Authors thank support from the intramural grants at TIFR Hyderabad from the Department of Atomic Energy (DAE). RS thanks Sumit Bawari for helpful discussion about DFT calculations. Ravi K. Biroju and Wolfgang Theis acknowledge the Marie-Sklodowska-Curie individual fellowship under EU H2020 Programme (H2020-MSCA-IF-2017; Grant No: 750929) to carry out some part of this work. AS acknowledges IIT Mandi for low temperature Raman PL facilities. Publisher Copyright: © 2020 The Author(s). Published by IOP Publishing Ltd


Original languageEnglish
Article number045001
JournalJPhys Materials
Issue number4
Publication statusPublished - 20 Aug 2020


  • 2D materials, Bi-excitons, Defect bound excitons, Density functional theory, Photoluminescence, Thermal conductivity, TMDs