Excitonic processes in atomically-thin MoSe2/MoS2 vertical heterostructures

Victor Carozo, Kazunori Fujisawa, Rahul Rao, Ethan Kahn, Jose Renato Cunha, Tianyi Zhang, Daniel Rubin, Mario Flores Salazar, Andrés De Luna Bugallo, Swastik Kar, Mauricio Terrones

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The relaxation of complex excitons in 2D materials is a topic of immense interest, due to their relevance in various optical and optoelectronic applications. In particular, relatively little is known regarding the dynamics in directly-synthesized heterostructures of dissimilar 2D materials, which are prototype architectures for atomically-thin optoelectronic devices. In this work, we have investigated vertical heterostructures (VH) of as-grown MoSe2 on MoS2. Specifically, we studied spatially-resolved photoluminescence at room and low temperatures, thermal stability and power dependence through photoluminescence spectroscopy combined with atomically resolved scanning transmission electron microscopy (STEM). The VH structure forms a Moiré pattern which was observed by high-resolution STEM imaging. At room temperature, we observed a tenfold suppression of the neutral exciton of MoSe2 in the VH area compared with individual MoSe2 layer, due to negative charge transfer from MoSe2 to MoS2. As a result, trions were found in MoS2. At low temperature, the intensity of the neutral exciton from the MoS2 in the VH area is suppressed. The thermal quenching of the neutral exciton at temperatures below 140 K is related to the trapping of the neutral excitons in mid-gap states induced by defects. These states are effective at trapping excitons to form bound excitons. Finally, using power dependence experiments, we identified three types of the excitonic complexes at 77 K besides the neutral exciton: trions, biexcitons and bound excitons.

Original languageEnglish (US)
Article number031016
Journal2D Materials
Volume5
Issue number3
DOIs
StatePublished - Jun 27 2018

Fingerprint

Excitons
Heterojunctions
excitons
Optoelectronic devices
trapping
Transmission electron microscopy
photoluminescence
LDS 751
Dissimilar materials
Temperature
transmission electron microscopy
Scanning electron microscopy
scanning electron microscopy
turbogenerators
Photoluminescence spectroscopy
room temperature
optoelectronic devices
Charge transfer
Quenching
Photoluminescence

All Science Journal Classification (ASJC) codes

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

Cite this

Carozo, V., Fujisawa, K., Rao, R., Kahn, E., Cunha, J. R., Zhang, T., ... Terrones, M. (2018). Excitonic processes in atomically-thin MoSe2/MoS2 vertical heterostructures. 2D Materials, 5(3), [031016]. https://doi.org/10.1088/2053-1583/aacbe8
Carozo, Victor ; Fujisawa, Kazunori ; Rao, Rahul ; Kahn, Ethan ; Cunha, Jose Renato ; Zhang, Tianyi ; Rubin, Daniel ; Salazar, Mario Flores ; De Luna Bugallo, Andrés ; Kar, Swastik ; Terrones, Mauricio. / Excitonic processes in atomically-thin MoSe2/MoS2 vertical heterostructures. In: 2D Materials. 2018 ; Vol. 5, No. 3.
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Carozo, V, Fujisawa, K, Rao, R, Kahn, E, Cunha, JR, Zhang, T, Rubin, D, Salazar, MF, De Luna Bugallo, A, Kar, S & Terrones, M 2018, 'Excitonic processes in atomically-thin MoSe2/MoS2 vertical heterostructures', 2D Materials, vol. 5, no. 3, 031016. https://doi.org/10.1088/2053-1583/aacbe8

Excitonic processes in atomically-thin MoSe2/MoS2 vertical heterostructures. / Carozo, Victor; Fujisawa, Kazunori; Rao, Rahul; Kahn, Ethan; Cunha, Jose Renato; Zhang, Tianyi; Rubin, Daniel; Salazar, Mario Flores; De Luna Bugallo, Andrés; Kar, Swastik; Terrones, Mauricio.

In: 2D Materials, Vol. 5, No. 3, 031016, 27.06.2018.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Excitonic processes in atomically-thin MoSe2/MoS2 vertical heterostructures

AU - Carozo, Victor

AU - Fujisawa, Kazunori

AU - Rao, Rahul

AU - Kahn, Ethan

AU - Cunha, Jose Renato

AU - Zhang, Tianyi

AU - Rubin, Daniel

AU - Salazar, Mario Flores

AU - De Luna Bugallo, Andrés

AU - Kar, Swastik

AU - Terrones, Mauricio

PY - 2018/6/27

Y1 - 2018/6/27

N2 - The relaxation of complex excitons in 2D materials is a topic of immense interest, due to their relevance in various optical and optoelectronic applications. In particular, relatively little is known regarding the dynamics in directly-synthesized heterostructures of dissimilar 2D materials, which are prototype architectures for atomically-thin optoelectronic devices. In this work, we have investigated vertical heterostructures (VH) of as-grown MoSe2 on MoS2. Specifically, we studied spatially-resolved photoluminescence at room and low temperatures, thermal stability and power dependence through photoluminescence spectroscopy combined with atomically resolved scanning transmission electron microscopy (STEM). The VH structure forms a Moiré pattern which was observed by high-resolution STEM imaging. At room temperature, we observed a tenfold suppression of the neutral exciton of MoSe2 in the VH area compared with individual MoSe2 layer, due to negative charge transfer from MoSe2 to MoS2. As a result, trions were found in MoS2. At low temperature, the intensity of the neutral exciton from the MoS2 in the VH area is suppressed. The thermal quenching of the neutral exciton at temperatures below 140 K is related to the trapping of the neutral excitons in mid-gap states induced by defects. These states are effective at trapping excitons to form bound excitons. Finally, using power dependence experiments, we identified three types of the excitonic complexes at 77 K besides the neutral exciton: trions, biexcitons and bound excitons.

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Carozo V, Fujisawa K, Rao R, Kahn E, Cunha JR, Zhang T et al. Excitonic processes in atomically-thin MoSe2/MoS2 vertical heterostructures. 2D Materials. 2018 Jun 27;5(3). 031016. https://doi.org/10.1088/2053-1583/aacbe8