Issue 19, 2022

Tunable ultrafast electron transfer in WSe2–graphene heterostructures enabled by atomic stacking order

Abstract

Efficient interfacial light-electric interconversion in van der Waals (vdW) heterostructures is crucial for their optoelectronic applications. However, an in-depth understanding of the necessary process for device operation, namely interfacial charge transfer (CT), has thus far remained elusive. In this study, by using photon energy-dependent transient THz spectroscopy, we complementarily investigate the interfacial CT process in heterostructures comprising monolayers of WSe2 and graphene with varying stacking orders on a sapphire substrate. We observe that the CT mechanism of the sub-A-exciton excitation is different from that of the above-A-exciton excitation. Notably, the CT process occurs via a photo-thermionic emission for sub-A-exciton excitations and a direct electron (or hole) transfer for above-A-exciton excitations. Furthermore, we demonstrate that the effective electric field induced by the sapphire substrate could adjust the Schottky barrier from a p-type contact (WSe2/Gr/sapphire) to an n-type contact (Gr/WSe2/sapphire). Consequently, it is more beneficial for the photo-thermionic electrons to transfer from graphene to WSe2 over the Schottky barrier in Gr/WSe2/sapphire. These results can provide new insights into the CT process in graphene–transition metal dichalcogenide (TMDC) vdW interfaces, which are critical to potential optoelectronic applications of graphene-TMDC heterostructures.

Graphical abstract: Tunable ultrafast electron transfer in WSe2–graphene heterostructures enabled by atomic stacking order

Supplementary files

Article information

Article type
Paper
Submitted
22 Nov 2021
Accepted
19 Apr 2022
First published
20 Apr 2022

Nanoscale, 2022,14, 7418-7425

Tunable ultrafast electron transfer in WSe2–graphene heterostructures enabled by atomic stacking order

X. Xing, Z. Zhang, C. Quan, L. Zhao, C. Wang, T. Jia, J. Ren, J. Du and Y. Leng, Nanoscale, 2022, 14, 7418 DOI: 10.1039/D1NR07698A

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