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Proceedings Paper

Understanding variations in circularly polarized photoluminescence in monolayer transition metal dichalcogenides (Conference Presentation)
Author(s): Kathleen McCreary; Aubrey Hanbicki; Marc Currie; Hsun-Jen Chuang; Berend Jonker
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Paper Abstract

The unique electronic band structure in monolayer transition metal dichalcogenides (TMDs) provides the ability to selectively populate a desired valley by exciting with circularly polarized light. The valley population is reflected through the circular polarization of photoluminescence (PL) and a high degree of circular polarization has been theoretically predicted for resonant excitation of TMDs such as MoS2, MoSe2, WS2 and WSe2, yet rarely observed experimentally. In fact, a wide range of values for the degree of circularly polarized emission, Pcirc, has been reported for monolayer TMDs, although the reasons for the disparity are unclear. Here we investigate the room-temperature Pcirc in TMD monolayers synthesized via chemical vapor deposition. In each material system, a wide range of Pcirc and PL intensity values are observed. However, there is a pronounced inverse correlation between Pcirc and PL intensity, which we attribute to sample-dependent variations in the exciton radiative and non-radiative lifetime components. Samples that demonstrate weak PL emission and short exciton relaxation time exhibit a high degree of valley polarization. The short exciton lifetime results in a higher measured polarization by limiting opportunity for depolarizing scattering events. These findings clarify the disparities among previously reported values and suggest a means to engineer valley polarization via controlled introduction of defects and non-radiative recombination sites.

Paper Details

Date Published: 18 September 2018
Proc. SPIE 10732, Spintronics XI, 1073228 (18 September 2018); doi: 10.1117/12.2320733
Show Author Affiliations
Kathleen McCreary, U.S. Naval Research Lab. (United States)
Aubrey Hanbicki, U.S. Naval Research Lab. (United States)
Marc Currie, U.S. Naval Research Lab. (United States)
Hsun-Jen Chuang, U.S. Naval Research Lab. (United States)
Berend Jonker, U.S. Naval Research Lab. (United States)

Published in SPIE Proceedings Vol. 10732:
Spintronics XI
Henri-Jean Drouhin; Jean-Eric Wegrowe; Manijeh Razeghi; Henri Jaffrès, Editor(s)

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