December 1 - 6, 2024
Boston, Massachusetts
Symposium Supporters
2024 MRS Fall Meeting & Exhibit
EL03.12.15

Indirect-to-Direct Bandgap Crossover and Room-Temperature Valley Polarization of Multilayer MoS2 Achieved by Electrochemical Intercalation

When and Where

Dec 4, 2024
8:00pm - 10:00pm
Hynes, Level 1, Hall A

Presenter(s)

Co-Author(s)

Seungwoo Song1,Min-kyung Jo1,2,Eunji Lee3,Jeongyong Kim3,Kibum Kang2

Korea Research Institute of Standards and Science1,Korea Advanced Institute of Science and Technology2,Sungkyunkwan University3

Abstract

Seungwoo Song1,Min-kyung Jo1,2,Eunji Lee3,Jeongyong Kim3,Kibum Kang2

Korea Research Institute of Standards and Science1,Korea Advanced Institute of Science and Technology2,Sungkyunkwan University3
Monolayer (1L) group VI transition metal dichalcogenides (TMDs) exhibit broken inversion symmetry and strong spin-orbit coupling, offering promising applications in optoelectronics and valleytronics. Despite their direct bandgap, high absorption coefficient, and spin-valley locking in K or K’ valleys, the ultra-short valley lifetime limits their room-temperature applications. In contrast, multilayer TMDs, with more absorptive layers, sacrifice the direct bandgap and valley polarization upon gaining inversion symmetry from the bilayer structure. We demonstrate that multilayer MoS2 can maintain 1) a structure with broken inversion symmetry and strong spin-orbit coupling, 2) a direct bandgap with high photoluminescence (PL) intensity, and 3) stable valley polarization up to room temperature. Through the intercalation of organic 1-ethyl-3- methylimidazolium (EMIM+) ions, multilayer MoS2 not only exhibits layer decoupling but also benefits from an electron doping effect. This results in a hundredfold increase in PL intensity and stable valley polarization, achieving 55% and 16% degrees of valley polarization at 3 K and room temperature, respectively. The persistent valley polarization at room temperature, due to interlayer decoupling and trion dominance facilitated by a gate-free method, opens up potential applications in valley-selective optoelectronics and valley transistors.

Keywords

electrochemical synthesis | van der Waals

Symposium Organizers

Deji Akinwande, The University of Texas at Austin
Cinzia Casiraghi, University of Manchester
Carlo Grazianetti, CNR-IMM
Li Tao, Southeast University

Session Chairs

Cinzia Casiraghi
Carlo Grazianetti

In this Session