Nonvolatile Control of Valley Polarized Emission in 2D WSe2‑AlScN Heterostructures

• Published in: ACS nano Vol. 18; no. 27; pp. 17958 - 17968
• Main Authors: Singh, Simrjit, Kim, Kwan-Ho, Jo, Kiyoung, Musavigharavi, Pariasadat, Kim, Bumho, Zheng, Jeffrey, Trainor, Nicholas, Chen, Chen, Redwing, Joan M., Stach, Eric A., Olsson, Roy H., Jariwala, Deep
• Format: Journal Article
• Language: English
• Published: American Chemical Society 09.07.2024
• Subjects: ferroelectric; valley-polarization; WSe2; nitrides; non-volatile
• ISSN: 1936-0851; 1936-086X; 1936-086X
• DOI: 10.1021/acsnano.4c04684

Achieving robust and electrically controlled valley polarization in monolayer transition metal dichalcogenides (ML-TMDs) is a frontier challenge for realistic valleytronic applications. Theoretical investigations show that the integration of 2D materials with ferroelectrics is a promising strategy; however, an experimental demonstration has remained elusive. Here, we fabricate ferroelectric field-effect transistors using a ML-WSe2 channel and an Al0.68Sc0.32N (AlScN) ferroelectric dielectric and experimentally demonstrate efficient tuning as well as non-volatile control of valley polarization. We measure a large array of transistors and obtain a maximum valley polarization of ∼27% at 80 K with stable retention up to 5400 s. The enhancement in the valley polarization is ascribed to the efficient exciton-to-trion (X-T) conversion and its coupling with an out-of-plane electric field, viz., the quantum-confined Stark effect. This changes the valley depolarization pathway from strong exchange interactions to slow spin-flip intervalley scattering. Our research demonstrates a promising approach for achieving non-volatile control over valley polarization for practical valleytronic device applications.