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Published January 20, 2022 | Accepted Version + Supplemental Material
Journal Article Open

Electrically Tunable and Dramatically Enhanced Valley-Polarized Emission of Monolayer WS₂ at Room Temperature with Plasmonic Archimedes Spiral Nanostructures


Monolayer transition metal dichalcogenides (TMDs) have intrinsic valley degrees of freedom, making them appealing for exploiting valleytronic applications in information storage and processing. WS₂ monolayer possesses two inequivalent valleys in the Brillouin zone, each valley coupling selectively with a circular polarization of light. The degree of valley polarization (DVP) under the excitation of circularly polarized light (CPL) is a parameter that determines the purity of valley polarized photoluminescence (PL) of monolayer WS₂. Here efficient tailoring of valley-polarized PL from monolayer WS₂ at room temperature (RT) through surface plasmon–exciton interactions with plasmonic Archimedes spiral (PAS) nanostructures is reported. The DVP of WS₂ at RT can be enhanced from <5% to 40% and 50% by using 2 turns (2T) and 4 turns (4T) of PAS, respectively. Further enhancement and control of excitonic valley polarization is demonstrated by electrostatically doping monolayer WS₂. For CPL on WS₂–2TPAS heterostructures, the 40% valley polarization is enhanced to 70% by modulating the carrier doping via a backgate, which may be attributed to the screening of momentum-dependent long-range electron–hole exchange interactions. The manifestation of electrically tunable valley-polarized emission from WS₂–PAS heterostructures presents a new strategy toward harnessing valley excitons for application in ultrathin valleytronic devices.

Additional Information

© 2021 Wiley-VCH GmbH. Issue Online: 21 January 2022; Version of Record online: 28 November 2021; Accepted manuscript online: 01 November 2021; Manuscript revised: 03 October 2021; Manuscript received: 25 June 2021. This work was jointly supported by the Army Research Office under the Multi-University Research Initiative (MURI) program (award #W911NF-16-1-0472) and the National Science Foundation under the Physics Frontier Center program for Institute for Quantum Information and Matter (IQIM) at the California Institute of Technology (award #1733907). The authors are also grateful for the support from the Beckman Institute at the California Institute of Technology for access to facilities at the Molecular Materials Research Center. W.-H.L. acknowledges a graduate fellowship from the J. Yang Family Foundation. P.C.W. acknowledges the support from the Ministry of Science and Technology (MOST), Taiwan (Grant number: 107-2923-M-006-004-MY3; 108-2112-M-006-021-MY3; 110-2124-M-006-004), and in part from the Higher Education Sprout Project of the Ministry of Education (MOE) to the Headquarters of University Advancement at National Cheng Kung University (NCKU). P.C.W. also acknowledges the support from the Ministry of Education (Yushan Young Scholar Program). The authors also thank Wen-Hui Cheng for training on the atomic layer deposition (ALD) system. The authors declare no conflict of interest. Data Availability Statement: Research data are not shared.

Attached Files

Accepted Version - adma.202104863_acc.pdf

Supplemental Material - adma202104863-sup-0001-suppmat.pdf


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August 22, 2023
October 23, 2023