Researchers identify ultra-fast dynamics in monolayer MoS₂ / ReSe₂ heterostructures

Forskere identificerer ultrahurtig dynamik i monolag MoS2/ReSe2 heterostrukturer

Measured THz electric field waveforms emitted from ReSe2/Moss2 and MoS2/ ReSe2 heterostructures with 800 nm pump excitation. Credit: Yang Jin

A collaborative team led by Prof. Su Fuhai of the Hefei Institutes of Physical Science (HFIPS) at the Chinese Academy of Sciences (CAS) recently identified the ultra-rapid dynamics of monolayer MoS2/ ReSe2 heterostructures.

After studying the ultra-fast carrier dynamics of this heterostructure, the researchers identified the relaxation pathways and intermediate processes of carrier transfer, free carrier development and interlayer exciton, etc. within different time scales ranging from sub-picoseconds to hundreds of picoseconds. The results are published in ACS Nano.

The construction of van der Waals (vdW) heterostructures, using various two-dimensional (2D) transition metal dichalcogenides (TMDs) films, provides a promising way to tailor the physical properties of individual layers and further expand their application in photoelectric devices. . Meanwhile, understanding the dynamics of photo carriers in vdW 2-D-TMDs, including various intermediate excitation species and relaxation pathways, play significant roles in the development of devices.

The complete scenario of photocarrier dynamics, especially in the heterostructures of the Rhenium dichalcogenides-based 2D-TMD, which are important in the near-infrared spectrum polarization-sensitive photoelectric devices, remains intangible until further notice.

Forskere identificerer ultrahurtig dynamik i monolag MoS2/ReSe2 heterostrukturer

Time-resolved and frequency-resolved THz photoconductivity excited with 800 nm pump pulses in ReSe2 monolayer and MoS2-ReSe2 heterostructures. Credit: Yang Jin

In this research, with vertically stacked heterostructures on a large scale manufactured by their collaborators, the researchers examined the dynamics of photo carriers via THz emission spectroscopy, time-resolved THz spectroscopy, and near-infrared optical pump probe spectroscopy, which enabled the direct probe of out-of-plane charge transfer. (CT), in-plane charge transport and interband transition.

Supported by the theory calculations and simulations, they established the path of photocarrier dynamics across charge separation, including the initial CT, intermediate evolution from free electron-hole plasma to interlayer excitons and free-carrier capture, as well as the long-lived interexciton recombination.

CT tends to significantly increase transient THz photoconductivity (~ 2.8-fold), non-linear saturable absorption (~ 5-fold), and interband recombination lifetime (> 10-fold) in the heterostructures compared to the isolated ReSe2 monolayer, which is most interesting to them as it demonstrated the wide range tuning in photocarrier dynamics based on the heterostructural construction.

This work provides comprehensive insight into the dynamics of photo carriers across charge separation, and it will help with the development of optoelectronic devices based on ReSe.2-Moss2 heterostructures.

Intermediate layer excitation formation, relaxation and transport in TMD’s van der Waals heterostructures

More information:
Jin Yang et al., Identification of the intermediate free carrier dynamics across the tax separation in monolayer MoS2 / ReSe2 heterostructures, ACS Nano (2021). DOI: 10.1021 / acsnano.1c06822

Provided by the Chinese Academy of Sciences

Citation: Researchers Identify Ultrafast Dynamics in Monolayer MoS₂ / ReSe₂ Heterostructures (2021, November 1) Retrieved November 1, 2021 from

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