Lattice Expansion Enables Large Surface Carrier Diffusion in WS<sub>2</sub> Monolayer

Two-dimensional (2D) materials hold great promise for next-generation optoelectronic devices, with photogenerated charge carrier transport being critical to their performance. However, the influence of photoexcitation-induced commensurate lattice thermal effects on surface charge carrier dynamics is poorly understood. Traditional photon-pump/photon-probe methods have constraints in capturing the subtle yet critical surface dynamics, especially for these ultrathin materials due to challenges in spatial resolution and penetration depth. In this study, we utilized scanning ultrafast electron microscopy (SUEM), a technique that offers unparalleled sensitivity to surface phenomena that are entirely inaccessible through other methods. Our findings reveal a ∼1.4% negative thermal expansion at elevated temperatures, inducing internal strain that modifies the electronic structure and significantly enhances surface carrier transport, resulting in an order-of-magnitude improvement in photodetection performance. Moreover, we demonstrate that photoinduced charge carrier diffusion occurs predominantly within the first tens of picoseconds after photoexcitation, a regime characterized by thermal excitation resulting from carrier–phonon interactions. These results establish a direct link among lattice thermal expansion, carrier dynamics, and optoelectronic performance.

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Publication Details

Journal
ACS Energy Letters
Published
2025-03-17
DOI
https://doi.org/10.1021/acsenergylett.5c00307
Citations
7
Primary Topic
2D Materials and Applications
Type
article
Field-Weighted Citation Impact
3.62

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article

Lattice Expansion Enables Large Surface Carrier Diffusion in WS2 Monolayer

Tulai Sun, Omar F. Mohammed, Haiting Cai, Osman M. Bakr et al.
7 citations
ACS Energy Letters
2D Materials and Applications
3.62
article

Lattice Expansion Enables Large Surface Carrier Diffusion in WS2 Monolayer

Tulai Sun, Omar F. Mohammed, Haiting Cai, Osman M. Bakr, Xiangming Xu, Bingyao Shao, Husam Niman Alshareef, Hongwei Zhu, Jun Yin, Yue Liu, Lijie Wang, Jie Yang, Yihan Zhu
article en
7 citations

Abstract

Two-dimensional (2D) materials hold great promise for next-generation optoelectronic devices, with photogenerated charge carrier transport being critical to their performance. However, the influence of photoexcitation-induced commensurate lattice thermal effects on surface charge carrier dynamics is poorly understood. Traditional photon-pump/photon-probe methods have constraints in capturing the subtle yet critical surface dynamics, especially for these ultrathin materials due to challenges in spatial resolution and penetration depth. In this study, we utilized scanning ultrafast electron microscopy (SUEM), a technique that offers unparalleled sensitivity to surface phenomena that are entirely inaccessible through other methods. Our findings reveal a ∼1.4% negative thermal expansion at elevated temperatures, inducing internal strain that modifies the electronic structure and significantly enhances surface carrier transport, resulting in an order-of-magnitude improvement in photodetection performance. Moreover, we demonstrate that photoinduced charge carrier diffusion occurs predominantly within the first tens of picoseconds after photoexcitation, a regime characterized by thermal excitation resulting from carrier–phonon interactions. These results establish a direct link among lattice thermal expansion, carrier dynamics, and optoelectronic performance.

ACS Energy LettersVol. 10(4)
Ministry of Education of the People's Republic of China (CN), Hong Kong Polytechnic University (HK), Zhengzhou University (CN), Renewable Energy Systems (United States) (US), Green Chemistry (PL), Zhejiang University of Technology (CN), King Abdullah University of Science and Technology (SA)
National Natural Science Foundation of China, Research Grants Council, University Grants Committee, King Abdullah University of Science and Technology, Hong Kong Polytechnic University, Natural Science Foundation of Henan Province, National Key Research and Development Program of China, Key Scientific Research Project of Colleges and Universities in Henan Province
Affordable and clean energy
Openalex Percentile: Top 7%
2D Materials and Applications
3.62
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