Quantum plasmonic two-dimensional WS-MoS heterojunction

• Published in: Nanoscale 2023-04, Vol.15 (16), p.7318-7328
• Main Authors: Ambardar, Sharad, Withers, Zachary H, Liu, Jiru, Lai, Xiaoyi, Albagami, Abdullah, Zhukova, Alina, Fabris Capelli, Pedro, Sahoo, Prasana K, Voronine, Dmitri V
• Format: Article
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/d3nr00861d

Two-dimensional heterostructures have recently gained broad interest due to potential applications in optoelectronic devices. Their reduced dimensionality leads to novel physical effects beyond conventional bulk electronics. However, the optical properties of the 2D lateral heterojunctions have not been completely characterized due to the limited spatial resolution, requiring nano-optical techniques beyond the diffraction limit. Here, we investigate lateral monolayer WS 2 -MoS 2 heterostructures in a plasmonic Au-Au tip-substrate picocavity using subdiffraction limited tip-enhanced photoluminescence (TEPL) spectroscopy with sub-nanometer tip-sample distance control. We observed more than 3 orders of magnitude PL enhancement by placing a plasmonic Au-coated tip at the resonantly excited heterojunction. We developed a theoretical model of the quantum plasmonic 2D heterojunction, where tunneling of hot electrons between the Au tip and MoS 2 leads to the quenching of the MoS 2 PL, while simultaneously increasing the WS 2 PL, in contrast to the non-resonant reverse transfer. Our simulations show good agreement with the experiments, revealing a range of parameters and enhancement factors corresponding to the switching between the classical and quantum regimes. The controllable photoresponse of the 2D heterojunction can be used in novel nanodevices. Quantum plasmonics enhance photoluminescence in two-dimensional heterostructures.