Strain Engineering for exciton dynamics: Exciton funneling in 2D artificial potential landscapes decorated by reassembled micro-bubbles

The joint team from Nankai University and Peking University has proposed a novel approach using annealing-driven reassembly of micro-bubbles to engineer controllable artificial potential landscapes in atomically thin semiconductors. This technique facilitates active spatiotemporal control of exciton dynamics at room temperature, opening new avenues for high-performance sensing, energy harvesting, and quantum information processing.

In the post-Moore era, excitonic devices have emerged as promising candidates to overcome the limitations of conventional electronic and photonic elements in operational speed and integration capabilities. Transition metal dichalcogenides (TMDs) have garnered significant attention due to their high binding energy and tunable valley degrees of freedom, making them ideal platforms for exploring excitonic physics and devices at room temperature. However, actively controlling exciton transport and dynamics within 2D energy landscapes remains a major challenge, hindering the advancement of practical excitonic devices.

The Solution:The joint team has engineered artificial potential landscapes in atomically thin semiconductors through annealing-driven reassembly of microbubbles.. This approach enables precise modulation of exciton dynamics via strain-induced potential wells, offering a powerful tool for developing practical excitonic devices.. By correlating micro-photoluminescence (PL) mappings with strain maps derived from AFM topography and strain modeling, the researchers demonstrated efficient localized exciton emission and spectral exciton funneling. Spatial imaging confirmed that excitons migrate towards bubble centers, driven by  both conventional diffusion and strain gradient-induced drift, a phenomenon accurately described by a customized drift-diffusion model.

The study reveals that minor surface fluctuations in WSe₂/hBN heterostructures merge into stable microbubbles after four annealing cycles, significantly reducing interfacial roughness. At the bubble apex, a maximum biaxial tensile strain of approximately 0.60% induces localized exciton states. Photoluminescence mapping shows efficient exciton funneling into low-energy states 30–61 meV below the primary exciton, with excitons migrating toward high-strain regions even when excited several micrometers away. Numerical simulations confirm that in strain-gradient regions, drift dominates over diffusion, validating the observed directional exciton transport.

The Future: The annealing-driven micro-bubble assembly for controlling exciton dynamics in 2D energy landscapes opens up a series of promising scenarios:
1. Actively control micro-bubbles on demand.
2. Enhanced performance of optoelectronic devices.
3. Dynamic strain engineering for exciton control.

The Impact: This research paves the way for actively controlling micro-bubbles on demand, enhancing the performance of optoelectronic devices, and achieving dynamic strain engineering for exciton control in spatio-temporal.

The research has been recently published in the online edition of Materials Futures, a prominent international journal in the field of interdisciplinary materials science research.

Reference: Wenqi Qian, Haiyi Liu, Guangyi Tao, Fangxun Liu, Sihan Lin, Tengteng Gao, Xueying Wang, Qihong Hu, Dalin Zhang, Dong Xiang, Lie Lin, Pengfei Qi, Zheyu Fang, Weiwei Liu. Exciton funneling in 2D artificial potential landscapes decorated by reassembled micro-bubbles[J]. Materials Futures. DOI: 10.1088/2752-5724/adc8c1

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