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Nonlinear Nano-Imaging of Interlayer Coupling in 2D Graphene-Semiconductor Heterostructures
Wenjin Luo1,2, Renkang Song1, Benjamin G Whetten2
1MOE Key Laboratory of Advanced Micro-Structured Materials, Shanghai Frontiers Science Center of Digital Optics, Institute of Precision Optical Engineering and School of Physics Science and Engineering Tongji University, Shanghai, 200092, China.
Small (Weinheim an Der Bergstrasse, Germany)
|January 27, 2024
Summary
Energy transfer, not charge transfer, dominates optical responses in 2D heterostructures. This study uses nanoscale imaging and modeling to measure interlayer energy transfer times, even with sample defects.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- Quantum properties of 2D heterostructures depend on interlayer coupling and charge/energy transfer.
- Interlayer dynamics are sensitive to structural variations like defects and grain boundaries.
- Distinguishing between charge and energy transfer is challenging due to nanoscale heterogeneities.
Purpose of the Study:
- To resolve intra- and inter-layer dynamics in graphene/WSe2 heterostructures.
- To differentiate between charge and energy transfer mechanisms.
- To measure interlayer energy transfer times independent of structural defects.
Main Methods:
- Utilized nanoscale imaging with coherent four-wave mixing (FWM) and incoherent two-photon photoluminescence (2PPL).
- Employed a tip distance-dependent coupled rate equation model.
- Incorporated hexagonal boron nitride (hBN) spacer layers to control interlayer distance.
Main Results:
- Demonstrated that energy transfer, rather than charge transfer, governs the interlayer-coupled optical response.
- Observed distinct tip-sample distance-dependent modifications in interlayer and intralayer relaxation via nano-FWM and -2PPL.
- Derived an interlayer energy transfer time of ~1 ps, consistent with existing literature.
Conclusions:
- Energy transfer is the dominant mechanism in the optical response of these 2D heterostructures.
- The combined imaging and modeling approach can determine intrinsic sample properties despite heterogeneity.
- This technique offers a pathway to precisely characterize interlayer dynamics in complex 2D materials.
